Status of freshwater catfish populations and their habitat within the Cockburn River

Status of freshwater catfish populations and their habitat within the Cockburn River

Craig Boys, Meaghan Rourke, Wayne Robinson, Dean Gilligan and Isabelle Thiebaud

NSW Department of Primary Industries Port Stephens Fisheries Institute

Locked Bag 1, Nelson Bay, NSW, 2315 Australia

Final report for the Namoi Catchment Management Authority

September 2011

Status of freshwater catfish populations and their habitat within the Cockburn River September 2011 Authors: Craig Boys, Meaghan Rourke, Wayne Robinson. Dean Gilligan and Isabelle Thiebaud Published By: NSW Department of Primary Industries Postal Address: Cronulla Fisheries Research Centre of Excellence, PO Box 21, Cronulla, NSW, 2230 Internet: www.dpi.nsw.gov.au

© Department of Primary Industries This work is copyright. Except as permitted under the Copyright Act, no part of this reproduction may be reproduced by any process, electronic or otherwise, without the specific written permission of the copyright owners. Neither may information be stored electronically in any form whatsoever without such permission. DISCLAIMER The publishers do not warrant that the information in this report is free from errors or omissions. The publishers do not accept any form of liability, be it contractual, tortuous or otherwise, for the contents of this report for any consequences arising from its use or any reliance placed on it. The information, opinions and advice contained in this report may not relate to, or be relevant to, a reader’s particular circumstance.

Contents i

Boys et al. Cockburn River catfish survey

TABLE OF CONTENTS

TABLE OF CONTENTS.................................................................................................................................I LIST OF TABLES.......................................................................................................................................... II LIST OF FIGURES ....................................................................................................................................... II ACKNOWLEDGEMENTS..........................................................................................................................III NON-TECHNICAL SUMMARY ................................................................................................................IV 1. INTRODUCTION .................................................................................................................................. 1

1.1. Background and need .................................................................................................................... 1 1.2. Scope and objectives of research................................................................................................... 1

2. METHODS.............................................................................................................................................. 3 2.1. Study area ....................................................................................................................................... 3 2.2. Fish sampling and analyses............................................................................................................ 5 2.3. Habitat mapping............................................................................................................................. 7 2.4. Habitat analyses and comparison to inland NSW reference condition ..................................... 8

3. RESULTS10 3.1. Catfish surveys.............................................................................................................................. 10 3.2. Habitat surveys ............................................................................................................................. 13

4. DISCUSSION........................................................................................................................................ 15 5. CONCLUSIONS AND RECOMMENDATIONS.............................................................................. 18 6. REFERENCES...................................................................................................................................... 19 7. APPENDICES....................................................................................................................................... 21

7.1. Appendix 1 – Site photos.............................................................................................................. 21 7.2. Appendix 2 – Sites and habitat variables used in inland NSW catfish habitat reference

models.................................................................................................................................... 26 7.3. Appendix 3 - Habitat maps of study sites................................................................................... 28 7.4. Appendix 4 – Proposed future research options........................................................................ 42

ii Contents

Cockburn River catfish survey Boys et al.

LIST OF TABLES

Table 1. Fish sampling details and effort ........................................................................................... 5 Table 2. Habitat variables mapped for a 1 km section of each of the seven study sites..................... 7 Table 3. Catch summary from spring-summer 2010/11 fish surveys at the seven study sites in the Cockburn River. ............................................................................................................................... 12 Table 4. Summary of aquatic habitat variables obtained from 1km mapping of each of the study reaches. ............................................................................................................................................. 14 Table 5. Results of discriminant function analysis showing the probability that catfish should occur at a site based on the aquatic habitat surveys. .................................................................................. 14

LIST OF FIGURES

Figure 1. An adult catfish observed occupying a gravel nest in the lower Cockburn River during the current study....................................................................................................................................... 2 Figure 2. Map of the Cockburn River and study sites........................................................................ 3 Figure 3. Photo of the Broadwater showing typical habitat and geomorphology of upstream reaches (TOP) and downstream of Kootingal Bridge (BOTTOM) showing typical habitat of downstream reaches. ............................................................................................................................................... 4 Figure 4. Twelve month daily hydrograph showing discharge at Gauge 419099 (Cockburn River at Kootingal Bridge). Fish sampling dates are identified by dots and habitat mapping dates are identified by a star. Gauge data obtained from the NSW Government Water Information Website (http://waterinfo.nsw.gov.au/). ........................................................................................................... 6 Figure 5. Typical deployment of fyke net. ......................................................................................... 6 Figure 6. Location of the 36 sites used to establish reference conditions for catfish habitat across inland NSW (source: Rourke, Gilligan and Robinson, unpublished). ............................................... 8 Figure 7. Length-frequency histogram showing the size-class structure of the catfish population in the Cockburn River, sampled across all seven sites in the spring-summer of 2010/11. The red line shows the approximate age of catfish at each size (Davis 1977a).................................................... 10 Figure 8. Length-frequency histograms showing size class of catfish within each study site (Bates Place excluded due to absence of catfish). ....................................................................................... 11 Figure 9. Monthly hydrograph showing discharge at Gauge 419099 (Cockburn River at Kootingal Bridge) over the last five years. The spring-summer breeding seasons are shown. Gauge data obtained from the NSW Government Water Information Website (http://waterinfo.nsw.gov.au/). 13

Acknowledgements iii


ACKNOWLEDGEMENTS

This study was funded by the Namoi Catchment Management Authority. Many thanks are extended to Francesca Andreoni and Bronwyn Witts for their time spent on contract preparation and overseeing project delivery. Tony Fowler coordinated fish and habitat surveys. The authors greatly appreciate the local landholders who allowed access to the river from their property. Trent Alexander assisted with data entry and management and also prepared many of the data summaries and figures in this report. Neal Foster assisted greatly with site selection and establishing communication with local landholders. Bob Creese and Tracey McVea assisted with final editing and formatting of the report. All fish surveys were carried out in accordance with the Australian Code of Electrofishing Practice (Anon 1997) and Animal Care and Ethics Research Authority 05/06.

iv Non Technical Summary


NON-TECHNICAL SUMMARY

Status of freshwater catfish populations and their habitat within the Cockburn River

PRINCIPAL INVESTIGATORS: Dr Craig Boys ADDRESS: Industry & Investment NSW

Port Stephens Fisheries Institute Locked Bag 1, Nelson Bay, NSW, 2315 Telephone: 02 4981 1231 Fax: 02 4982 2265

NON TECHNICAL SUMMARY:

Freshwater or eel-tailed catfish (Tandanus tandanus) is an endangered native species that has suffered significant declines in both abundance and distribution throughout inland rivers of New South Wales (NSW). The species is bottom-dwelling and breeds by laying eggs in a semi-saucer shaped nest that is tended to by the male. This breeding strategy leaves eggs and larvae vulnerable to fluctuating water levels. Catfish have been shown to abandon nests when water level drops below critical levels and these fluctuations in water level can also impact on the spawning behaviour of females. This is of concern because failure to successfully breed across multiple seasons may compromise the sustainability of populations. This concern has been raised in the Cockburn River near Tamworth NSW, where some believe that water abstraction for irrigation from the nearby groundwater over summer and the subsequent impact of this on river levels may be causing catfish to abandon their nests. In response to these concerns, it has been proposed that research be undertaken as a way of determining whether water access rules for the Cockburn River are adequate for allowing successful catfish breeding. The purpose of this current study was to conduct a preliminary survey of the status of the catfish population and associated habitat within the Cockburn River and to consider options for further research aimed at determining if there is a link between water abstraction and catfish nest abandonment. To achieve this, catfish were sampled using boat electrofishing from seven sites in the Cockburn River in the spring-summer of 2010/11. In conjunction with these surveys, aquatic habitat was mapped at all sites and quantified for comparison to habitat reference models which have been developed across inland NSW to determine the quality of habitat for catfish. Based on this single survey, there is little evidence to suggest that there has been prolonged suppression of catfish recruitment in the Cockburn River. There was a wide size-range of fish present and these were distributed throughout the study reach. This finding was consistent with the results of habitat surveys, which indicated that habitat within the Cockburn River was typically of good quality to sustain catfish populations when compared to State-wide reference models. The absence of a particular size-class of catfish may indicate a possible failure to breed in the 2008/09 breeding season. However, it must be acknowledged that interpreting population data from a single survey can be misleading and, if greater certainty is required, then follow-up surveys are recommended.

Non Technical Summary v


It was also an objective of this study to consider options for future research aimed at quantifying the potential link between nest abandonment and water abstraction. Some of the techniques for mapping underwater habitat in low-visibility rivers (such as sonar) would be inappropriate for both locating catfish nests and determining their occupancy rates. Because of this, visual census appears the only reasonable alternative. A number of research objectives and methods have been outlined in this report and although each will provide important information in isolation, determining the link between water abstraction and nest abandonment in the Cockburn will likely require a combination of all of these approaches. KEYWORDS:

Breeding, Fish Community Survey, Habitat Mapping, Namoi, Nest Abandonment, Tandanus.

NSW DPI 1


1. INTRODUCTION

1.1. Background and need

The freshwater (or eel-tailed) catfish (Tandanus tandanus) occupies a wide range of habitats, including rivers, creeks, billabongs and lagoons, preferring sluggish or still waters (Clunie and Koehn 2001). The species is demersal (bottom dwelling) and spawns from spring to summer when water temperatures are above 24°C (Lake 1967). During breeding, pairs of individuals construct nests of gravel, rocks and occasionally mud and sticks (Cadwallader and Backhouse 1983). Spawning occurs after nest construction and males remain with the nest to tend to the eggs (Figure 1). Research in Lake Victoria has shown that nests are typically found in less than 1 m water depths (Clunie and Koehn 2001) and recent research of populations in the Nymboida River (north coast of NSW) support this assertion (Gavin Butler, Grafton Fisheries Centre, unpublished data). The Murray-Darling Basin population of freshwater catfish was gazetted as endangered within NSW waters in July 2009. Whilst records show that catfish were once widespread in the western rivers of NSW, being one of the most abundant species, there has been a significant and rapid decline in both abundance and distribution in recent decades (Harris and Gehrke 1997). One cause of this decline is believed to be reduced spawning and recruitment success due to alterations to flow patterns and flooding regimes (FSC 2008). There is evidence that alterations in water level can affect nest establishment and subsequent breeding success. In particular, a sudden drop in water level can expose nests, which may be subsequently abandoned by nesting males (Lake 1967, Clunie and Koehn 2001). Although males may construct an alternative nest, spawned eggs are left without parental care. it has also been shown that frequent drops in water levels which disturb nests can result in females reabsorbing oocytes and failing to spawn (Lake 1967). In the lower Cockburn River near Tamworth NSW, groundwater alluvium aquifers on the floodplain are highly connected to the surface water within the main channel (Cook et al. 2006). Because of this, surface flows in the river can be impacted by groundwater abstraction (Neal Foster, NSW Office of Water, pers. comm.). The degree to which this happens along the lower Cockburn varies due to the presence of low-level weirs which maintain disconnected pools which experience varying degrees of abstraction pressure. There is concern in some sectors of the community that water abstraction from the nearby groundwater alluvium during the summer irrigation season, and the subsequent lowering of pool depth in the main channel, may be causing catfish to abandon their nests (David Ward, NSW Department of Primary Industries (DPI) Tamworth, pers. comm.). Although such concerns remain unproven, controlled rearing experiments (Lake 1967) and similar reports of nest abandonment in the Nymboida River following falling water level (Gavin Butler, Grafton Fisheries Centre, personal communication) give some credence to this belief. In response to these concerns, NSW DPI has proposed that the ecological status of the threatened freshwater catfish in the Cockburn River catchment be updated in the report cards for public exhibition in water sharing plans and that a study be undertaken to scientifically ground-truth whether water access rules for the Cockburn River are adequate for successful catfish breeding.

1.2. Scope and objectives of research

Prior to considering a detailed study aimed at determining if, and to what degree, nest abandonment may be occurring in the Cockburn River, it was prudent to first investigate the status of catfish populations in this region. To this end, in the summer of 2010/11 catfish were sampled from seven

2 NSW DPI


pools in the lower Cockburn River to analyse the age-class structure of local populations and provide an indication of possible extent of recruitment in recent years. Subsequent to that, habitat at these sites was mapped and compared to a State-wide reference model used to define good catfish habitat based on presence/absence data. This was done with the objective of identifying whether habitat or some other variable may be responsible for the quantified level of recruitment detected in the survey. The final objective was to consider and recommend an appropriate approach to quantifying the impact of water abstraction on nest abandonment by catfish. It was also initially planned to investigate differences in catfish abundance and size-classes between individual pools in the Cockburn and start collecting data relating to depth variability and abstraction pressure in these individual pools. Unfortunately, significant flooding and a lack of abstraction during the study period prevented this. Recommendations are made regarding how best to incorporate these activities into future research.

Figure 1. An adult catfish observed occupying a gravel nest in the lower Cockburn River during the current study

NSW DPI 3


2. METHODS

2.1. Study area

The Cockburn River, is located in the Namoi Catchment in NSW. The river is 33.6 km in length and drains a sub-catchment approximately 1,130 km2 in area. It begins at the confluence of Swamp Oak Creek and Jamiesons Creek near the town of Limbri and falls approximately 109 m over its length, flowing south-westerly into the Peel River near Tamworth. Seven sites were chosen for the study, extending from the Broadwater, downstream to the Nemingha Bridge (Figure 2). The geomorphology of the river changes noticeably along its length with upper reaches dominated by granite bedrock and rocky outcrops, with coarse gravel and sand dominating lower reaches (Figure 3). The upper catchment of the Cockburn consists primarily of mixed native vegetation, dominated by Box gum woodlands and some areas of Cypress Pine. Much of the riparian zone in the lower alluvium floodplain has been cleared for irrigated crops and grazing. Flows in the Cockburn are intermittent and, over the past 20 years, the river has ceased flowing on 17 occasions (702 days) (Cook et al. 2006). There is a large degree of exchange between surface water and that in the hyporheic zone (subsurface or groundwater) and subsurface flows make an important contribution to river discharge (Cook et al. 2006). The river is unregulated, but a number of engineered rock weirs with partial width rock ramps help retain water in pools along its length. A number of private irrigators and graziers pump water directly from the river or via nearby bores and it has been estimated that 27 properties bordering the Cockburn River extract a total of about 8 × 105 m3/yr (Cook et al. 2006). Extraction is typically higher in the lower reaches of the river when compared to the upper reaches.

Figure 2. Map of the Cockburn River and study sites.

4 NSW DPI


Figure 3. Photo of the Broadwater showing typical habitat and geomorphology of upstream reaches (TOP) and downstream of Kootingal Bridge (BOTTOM) showing typical habitat of downstream reaches.

NSW DPI 5


2.2. Fish sampling and analyses

Electrofishing was conducted once at each site between November 2010 and January 2011 during daylight hours (Table 1). It was initially planned to complete all fish surveys within a fortnight, but this was prevented by a significant flood which was experienced in the middle of the survey (Figure 4). As a result four sites were not sampled until January, once water levels had subsided. Deeper water sites were sampled using a five metre, twin-hulled aluminium boat (research vessel Electricus) mounted with a Smith-Root 7.5 GPP electrofishing unit. Shallower sites were sampled with a smaller four metre flat-bottom boat (research vessel Pole Volt) mounted with a Smith Root 2.5 GPP electrofishing unit. Both boats had two Wisconsin array anodes suspended from the bow, creating a semi-hemispherical underwater electric field. Pulsed (120 pulses per second) direct electrical current (DC) was used due to the reduced tendency to produce strong and harmful muscular contractions in fish compared with alternating current (Snyder 2003). All other electrofishing settings were not standardised and were adjusted to achieve optimal catch efficiency for the given water conductivity. A total of 1080 electrofishing seconds (on time) was typically performed at each site, with total fishing effort divided into 12 sub-samples (or shots) and allocated across all samplable habitats. Fish were dip-netted from the water and placed in a live-well on the boat to recover until measured and returned alive to the water after each shot. Any fish positively identified but not dip-netted were also recorded. At each site, electrofishing was supplemented by setting four 6 mm mesh, single wing, circular, twin-funnel fyke nets. The only exception being at Bates Place where the flood resulted in a rapid overnight rise in water levels and the loss of all fyke nets. Two fyke nets were attached to the left bank and two to the right bank, pointing downstream and angled slightly towards the centre of the channel (Figure 5). The nets were set at dusk and collected within 2 hours following sunrise. All captured fish were processed and released as per electrofishing surveys. Length frequency histograms were generated for catfish caught across all seven study sites, to examine the abundance of different size cohorts sampled. As a guide to the possible age structure of the sampled population, this histogram was overlayed with a length-age relationship developed by Davis (1977a), derived from spine radius measurements of 480 mixed-sex Tandanus aged between one and eight years collected from the Gwydir River prior to the construction of Copeton Dam. Table 1. Fish sampling details and effort

Site name Date sampled Latitude Longtitude

Electrofishing vessel* and time

(sec) Fyke nets

Nemingha Bridge 30/11/2010 -31.1249 150.99092 BE 1080 4Riverdene 19/01/2011 -31.1058 151.00354 BPV 1080 4Newhaven Park 18/01/2011 -31.0757 151.03636 BPV 1080 4Kootingal Bridge 19/01/2011 -31.0636 151.05569 BPV 1080 4Mavis Place 30/11/2010 -31.0618 151.070234 BE 1080 4Bates Place 1/12/2010 -31.0540 151.09586 BE 1260 0Broadwater 18/01/2011 -31.0604 151.11334 BPV 1080 4

* NSW Fisheries Research Vessels: BE = Electricus, BPV = Pole Volt.

6 NSW DPI


0

1000

2000

3000

4000

5000

6000

7000

8000

9000

1/06/2

010

1/07/2

010

1/08/2

010

1/09/2

010

1/10/2

010

1/11/2

010

1/12/2

010

1/01/2

011

1/02/2

011

1/03/2

011

1/04/2

011

1/05/2

011

1/06/2

011

Dis

char

ge (M

L/d)

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

1/06/2

010

1/07/2

010

1/08/2

010

1/09/2

010

1/10/2

010

1/11/2

010

1/12/2

010

1/01/2

011

1/02/2

011

1/03/2

011

1/04/2

011

1/05/2

011

1/06/2

011

Dis

char

ge (M

L/d)

Figure 4. Twelve month daily hydrograph showing discharge at Gauge 419099 (Cockburn River at Kootingal Bridge). Fish sampling dates are identified by dots and habitat mapping dates are identified by a star. Gauge data obtained from the NSW Government Water Information Website (http://waterinfo.nsw.gov.au/).

Figure 5. Typical deployment of fyke net.

NSW DPI 7


2.3. Habitat mapping

Aquatic habitat was mapped for 1 km at each of the seven sites in January 2011. Attributes relating to geomorphology, hydrology, instream structure (e.g. large wood), aquatic and terrestrial vegetation and substratum (see Table 2 for the full list) were mapped within the bank-full river channel using hand-held PDA units (Dell Axim X51U and MIO Digi-walker pocket PC) with ESRI Arcpad 6.0.3 data acquisition software. Each PDA was linked to a Garmin 72 GPS unit via a bluetooth device (i.Trek Bluetooth Battery Adapter) and loaded with a 1: 50,000 topographical map to record positional data. The channel was divided down the thalweg and the left and right-hand side of the channel were mapped separately. Shallow and narrow reaches were mapped on foot, whereas deeper reaches were mapped from a canoe or kayak. All data were uploaded into a Geographic Information System for processing. Two additional variables were derived from existing spatial data layers; altitude and mean daily flow. Altitude at the downstream extent of the site was extrapolated from a 100 m grid-cell DEM of NSW. Average daily flow for each 1 km reach was derived from a stream network model (Janet Stein, unpublished data). Table 2. Habitat variables mapped for a 1 km section of each of the seven study sites Habitat variable Unit of measure Altitude Metres ASL Large complex snags (branching and >2 m) Count Large simple snags (non-branching and >2 m) Count Small complex snags (branching and ≤2 m) Count Small simple snags (non-branching and ≤2 m) Count Snag Pile Count Large complex rocks Count Large simple rocks Count Small complex rocks Count Small simple rocks Count Willow (Salix spp.) Count Erosion (length) Total length in m Undercut (length) Total length in m Free floating macrophytes Area (m2) Narrow-leaved emergent macrophytes Area (m2) Non-feathery submerged macrophytes Area (m2) Broad-leaved emergent macrophytes Area (m2) Floating attached macrophytes Area (m2) Submerged & emergent feathery macrophytes Area (m2) Maximum depth Metres Average Daily flow ML per day Pool (still or very slowly flowing water) Area (ha) Rapid (very turbulent with the presence of one or more abrupt drops in water level)

Area (ha)

Riffle (flowing water with a turbulent surface) Area (ha) Run (flowing water with little or no turbulence) Area (ha) Bedrock Area (ha) Boulder (> 512 mm diam.) Area (ha) Clay (< 62 µm and pliable) Area (ha) Cobble (64 – 512 mm diam.) Area (ha) Detritus (organic material) Area (ha) Gravel (2 – 64 mm diam.) Area (ha) Mud (< 62 µm diam. and dispersable) Area (ha) Sand (62 µm – 3 mm diam.) Area (ha)

8 NSW DPI


2.4. Habitat analyses and comparison to inland NSW reference condition

To establish whether the aquatic habitat mapped on the lower Cockburn can be considered to be ‘suitable’ catfish habitat, the Cockburn aquatic habitat data were compared to a reference model for catfish habitat established for inland NSW (Meaghan Rourke, Dean Gilligan and Wayne Robinson, NSW DPI, unpublished data). These models were constructed using habitat and catfish presence/absence data obtained during routine fish community surveys throughout NSW since the 1st of January 2000 (NSW DPI, Freshwater Fish Research Database, unpublished data). Thirty six sites were selected across the inland catchments of NSW (Figure 6 and Appendix 2: Table A2.1). Each site had been sampled using boat and/or backpack electrofishing multiples times. If a catfish had been found during the surveys the site was classified as ‘present’. If no catfish had been found, the site was classified as ‘disappeared’. If a young of year catfish (≤ 83 mm, based on Davis 1977a) had been caught during any of the surveys, then the site was classified as ‘breeding’. For the purpose of the current study, only the model relating to the presence/absence of catfish was used, because it most accurately indicates whether there may be a long-term absence of recruitment.

Site included in inland NSW reference modelSite included in inland NSW reference model

Figure 6. Location of the 36 sites used to establish reference conditions for catfish habitat across inland NSW (source: Rourke, Gilligan and Robinson, unpublished).

NSW DPI 9


Aquatic habitat was mapped for each of the 36 1 km reaches between August and September 2009. All the same attributes measured in the Cockburn were mapped in the same way. Some variables were merged. For example the different macrophyte types were classified as either submergent or emergent macrophyte, rapid and riffle were merged, bedrock and boulder were merged and cobble and gravel were merged. Variables that were not found at a minimum of 50% of the sites were removed from the model. Variables were tested for normality and those with many zero values were transformed to presence/absence. The remaining variables were transformed where appropriate. This left 19 potential variables for discriminating between the catfish categories (Appendix 2: Table A2.2). Of these, six variables correctly predicted (at 92% of sites) the presence or absence of catfish. Catfish were more likely to be present with increasing depth, area of bedrock-boulder, area of cobble-gravel, area of emergent macrophytes, length of eroded bank and number of small complex snags (Rourke, Gilligan and Robinson, unpublished). These habitat variables were used from the Cockburn data in a discriminant function analysis (within the SAS statistical package). A probability was calculated which indicated the probability that a site with that particular habitat composition would contain catfish. For example, if the probability was 50 %, then it would be expected that only half of the sites sampled with that habitat composition would contain catfish..

10 NSW DPI


3. RESULTS

3.1. Catfish surveys

A total of 8796 fish representing nine species were captured across all seven study sites in the spring-summer of 2010/11 (Table 3). By far the most abundant species sampled was carp gudgeon (n=8362), with fly-specked hardyhead (179) and carp (110) also being common. Freshwater catfish were moderately abundant (43), being sampled in all but one site (Bates Place). Bates place also had the lowest overall abundance of fish (44) relative to all other sites. A large size range of catfish was sampled across the study sites (Figure 7), with fish between 90 mm and 510 mm caught. Age-size models from nearby populations (Davis 1977a) suggest that these fish may be between one and six years of age. Smaller size classes were found in the most downstream site (Nemingha Bridge), although catches at each site were too low to sufficiently determine site-scale differences in size class structure. Adults greater than 380 mm or approximately 3-6 years of age dominated catches. The two-year old age cohort appeared absent from the catches. Monthly flow records obtained over the past five years show that the spring-summer months two years ago were characterised by above average flows (Figure 9).

0

1

2

3

4

5

6

7

8

9

10

20 40 60 80 100 120 140 160 180 200 220 240 260 280 300 320 340 360 380 400 420 440 460 480 500 520 540 560

Length (mm)

1

2

3

4

5

6

7

8

02.5% 5 %2.5% 2.5% 5 %2.5% 2.5% 7.5% 12.5% 10% 10%22.5% 15%

Freq

uenc

y

1

2

3

4

5

6

7

8

Appr

oxim

ate

age

(yea

rs)

0

1

2

3

4

5

6

7

8

9

10

20 40 60 80 100 120 140 160 180 200 220 240 260 280 300 320 340 360 380 400 420 440 460 480 500 520 540 560

Length (mm)

1

2

3

4

5

6

7

8

02.5% 5 %2.5% 2.5% 5 %2.5% 2.5% 7.5% 12.5% 10% 10%22.5% 15%

Freq

uenc

y

0

1

2

3

4

5

6

7

8

9

10

20 40 60 80 100 120 140 160 180 200 220 240 260 280 300 320 340 360 380 400 420 440 460 480 500 520 540 560

Length (mm)

1

2

3

4

5

6

7

8

0

1

2

3

4

5

6

7

8

02.5% 5 %2.5% 2.5% 5 %2.5% 2.5% 5 %2.5% 2.5%2.5% 2.5% 7.5% 12.5% 10% 10%22.5% 15%7.5% 12.5% 10% 10%22.5% 15%12.5% 10% 10%22.5% 15%

Freq

uenc

y

1

2

3

4

5

6

7

8

Appr

oxim

ate

age

(yea

rs)

Figure 7. Length-frequency histogram showing the size-class structure of the catfish population in the Cockburn River, sampled across all seven sites in the spring-summer of 2010/11. The red line shows the approximate age of catfish at each size (Davis 1977a).

NSW DPI 11


0

5

10

15

20

25

30

35

40

45

50

20 40 60 80 100 120 140 160 180 200 220 240 260 280 300 320 340 360 380 400 420 440 460 480 500 520 540 560

Total length (mm)

% C

atch

a) Nemingha Bridge

0

5

10

15

20

25

30

35

40

45

50

20 40 60 80 100 120 140 160 180 200 220 240 260 280 300 320 340 360 380 400 420 440 460 480 500 520 540 560

Total length (mm)

% C

atch

b) Riverdene

0

5

10

15

20

25

30

35

40

45

50

20 40 60 80 100 120 140 160 180 200 220 240 260 280 300 320 340 360 380 400 420 440 460 480 500 520 540 560

Total length (mm)

% C

atch

c) Newhaven Park

0

5

10

15

20

25

30

35

40

45

50

20 40 60 80 100 120 140 160 180 200 220 240 260 280 300 320 340 360 380 400 420 440 460 480 500 520 540 560

Total length (mm)

% C

atch

d) Kootingal Bridge

0

5

10

15

20

25

30

35

40

45

50

20 40 60 80 100 120 140 160 180 200 220 240 260 280 300 320 340 360 380 400 420 440 460 480 500 520 540 560

Total length (mm)

% C

atch

e) Mavis Place

0

5

10

15

20

25

30

35

40

45

50

20 40 60 80 100 120 140 160 180 200 220 240 260 280 300 320 340 360 380 400 420 440 460 480 500 520 540 560

Total length (mm)

% C

atch

f) Broadwater

0

5

10

15

20

25

30

35

40

45

50

20 40 60 80 100 120 140 160 180 200 220 240 260 280 300 320 340 360 380 400 420 440 460 480 500 520 540 560

Total length (mm)

% C

atch

a) Nemingha Bridge

0

5

10

15

20

25

30

35

40

45

50

20 40 60 80 100 120 140 160 180 200 220 240 260 280 300 320 340 360 380 400 420 440 460 480 500 520 540 560

Total length (mm)

% C

atch

a) Nemingha Bridge

0

5

10

15

20

25

30

35

40

45

50

20 40 60 80 100 120 140 160 180 200 220 240 260 280 300 320 340 360 380 400 420 440 460 480 500 520 540 560

Total length (mm)

% C

atch

b) Riverdene

0

5

10

15

20

25

30

35

40

45

50

20 40 60 80 100 120 140 160 180 200 220 240 260 280 300 320 340 360 380 400 420 440 460 480 500 520 540 560

Total length (mm)

% C

atch

b) Riverdene

0

5

10

15

20

25

30

35

40

45

50

20 40 60 80 100 120 140 160 180 200 220 240 260 280 300 320 340 360 380 400 420 440 460 480 500 520 540 560

Total length (mm)

% C

atch

c) Newhaven Park

0

5

10

15

20

25

30

35

40

45

50

20 40 60 80 100 120 140 160 180 200 220 240 260 280 300 320 340 360 380 400 420 440 460 480 500 520 540 560

Total length (mm)

% C

atch

c) Newhaven Park

0

5

10

15

20

25

30

35

40

45

50

20 40 60 80 100 120 140 160 180 200 220 240 260 280 300 320 340 360 380 400 420 440 460 480 500 520 540 560

Total length (mm)

% C

atch

d) Kootingal Bridge

0

5

10

15

20

25

30

35

40

45

50

20 40 60 80 100 120 140 160 180 200 220 240 260 280 300 320 340 360 380 400 420 440 460 480 500 520 540 560

Total length (mm)

% C

atch

d) Kootingal Bridge

0

5

10

15

20

25

30

35

40

45

50

20 40 60 80 100 120 140 160 180 200 220 240 260 280 300 320 340 360 380 400 420 440 460 480 500 520 540 560

Total length (mm)

% C

atch

e) Mavis Place

0

5

10

15

20

25

30

35

40

45

50

20 40 60 80 100 120 140 160 180 200 220 240 260 280 300 320 340 360 380 400 420 440 460 480 500 520 540 560

Total length (mm)

% C

atch

e) Mavis Place

0

5

10

15

20

25

30

35

40

45

50

20 40 60 80 100 120 140 160 180 200 220 240 260 280 300 320 340 360 380 400 420 440 460 480 500 520 540 560

Total length (mm)

% C

atch

f) Broadwater

0

5

10

15

20

25

30

35

40

45

50

20 40 60 80 100 120 140 160 180 200 220 240 260 280 300 320 340 360 380 400 420 440 460 480 500 520 540 560

Total length (mm)

% C

atch

f) Broadwater

Figure 8. Length-frequency histograms showing size class of catfish within each study site (Bates Place excluded due to absence of catfish).

Cockburn River catfish survey 12

Table 3. Catch summary from spring-summer 2010/11 fish surveys at the seven study sites in the Cockburn River.

Common Name Scientific Name E FN ST E FN ST E FN ST E FN ST E FN ST E FN ST E FN ST GTFreshwater catfish Tandanus tandanus 5 2 7 9 1 10 3 2 5 10 0 10 4 2 6 0 0 0 2 3 5 43Fly-specked hardyhead

Craterocephalus stercusmuscarum fulvus 0 83 83 0 6 6 0 57 57 0 32 32 0 1 1 0 0 0 0 0 0 179

Carp gudgeon Hypseleotris spp 38 4420 4458 4 781 785 39 673 712 6 491 497 57 916 973 24 0 24 16 897 913 8362Golden perch Macquaria ambigua 3 1 4 4 1 5 9 4 13 6 1 7 8 0 8 5 0 5 12 0 12 54Murray cod Maccullochella peelii 0 0 0 2 0 2 1 0 1 2 0 2 5 0 5 2 0 2 0 0 0 12Murray-Darling rainbowfish Melanotaenia fluviatilis 0 1 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1Australian smelt Retropinna semoni 1 0 1 0 0 0 14 0 14 0 0 0 0 1 1 0 0 0 16 0 16 32Carp Cyprinus carpio 7 0 7 19 0 19 2 0 2 11 0 11 24 0 24 16 0 16 31 0 31 110Mosquitofish Gambusia holbrooki 0 0 0 0 0 0 0 1 1 0 5 5 0 0 0 0 0 0 0 0 0 6

GT 54 4507 4561 38 789 827 68 737 805 35 529 564 98 920 1018 44 0 44 77 900 977 8796

Kootingal Br Mavis Place Bates Place BroadwaterRiverdeneNemingha Br Newhaven P

E =Electrofishing; FN = Fyke net; ST = Site total; and GT = Grand total

NSW DPI 13


0

200

400

600

800

1000

1200

1400

1/03/0

6

1/06/0

6

1/09/0

6

1/12/0

6

1/03/0

7

1/06/0

7

1/09/0

7

1/12/0

7

1/03/0

8

1/06/0

8

1/09/0

8

1/12/0

8

1/03/0

9

1/06/0

9

1/09/0

9

1/12/0

9

1/03/1

0

1/06/1

0

1/09/1

0

1/12/1

0

1/03/1

1

1/06/1

1

1/09/1

1

Date

Dis

char

ge (M

L/d)

06/07 08/09 09/10 10/1107/08

0

200

400

600

800

1000

1200

1400

1/03/0

6

1/06/0

6

1/09/0

6

1/12/0

6

1/03/0

7

1/06/0

7

1/09/0

7

1/12/0

7

1/03/0

8

1/06/0

8

1/09/0

8

1/12/0

8

1/03/0

9

1/06/0

9

1/09/0

9

1/12/0

9

1/03/1

0

1/06/1

0

1/09/1

0

1/12/1

0

1/03/1

1

1/06/1

1

1/09/1

1

Date

Dis

char

ge (M

L/d)

06/07 08/09 09/10 10/1107/08

0

200

400

600

800

1000

1200

1400

1/03/0

6

1/06/0

6

1/09/0

6

1/12/0

6

1/03/0

7

1/06/0

7

1/09/0

7

1/12/0

7

1/03/0

8

1/06/0

8

1/09/0

8

1/12/0

8

1/03/0

9

1/06/0

9

1/09/0

9

1/12/0

9

1/03/1

0

1/06/1

0

1/09/1

0

1/12/1

0

1/03/1

1

1/06/1

1

1/09/1

1

Date

Dis

char

ge (M

L/d)

0

200

400

600

800

1000

1200

1400

1/03/0

6

1/06/0

6

1/09/0

6

1/12/0

6

1/03/0

7

1/06/0

7

1/09/0

7

1/12/0

7

1/03/0

8

1/06/0

8

1/09/0

8

1/12/0

8

1/03/0

9

1/06/0

9

1/09/0

9

1/12/0

9

1/03/1

0

1/06/1

0

1/09/1

0

1/12/1

0

1/03/1

1

1/06/1

1

1/09/1

1

Date

Dis

char

ge (M

L/d)

06/07 08/09 09/10 10/1107/0806/07 08/09 09/10 10/1107/08

Figure 9. Monthly hydrograph showing discharge at Gauge 419099 (Cockburn River at Kootingal Bridge) over the last five years. The spring-summer breeding seasons are shown. Gauge data obtained from the NSW Government Water Information Website (http://waterinfo.nsw.gov.au/).

3.2. Habitat surveys

Detailed maps of habitat in each reach are presented in Appendix 3. From these the habitat of each reach was summarised so key variables could be included in the discriminant function analysis for comparison to the inland NSW reference models (Table 4). Based on this analysis all but one site was found to have aquatic habitat sufficient for the presence of catfish. The two most upper sites, Broadwater and Bates Place, were judged to have the most suitable catfish habitat (Table 5: p=0.90 and 0.94, respectively), whereas Riverdene was the only site where catfish were more likely to be absent than present based on habitat (Table 5: p=0.46).

14 NSW DPI


Table 4. Summary of aquatic habitat variables obtained from 1km mapping of each of the study reaches. Data type Site Name Broadwater Bates Place Mavis Place

Kootingal Bridge

Newhaven Park Riverdene

Nemingha Bridge

Altitude 455 441 424 421 416 399 396Count Large complex snags 15 10 21 35 17 39 11Count Large simple snags 30 3 19 34 12 38 14Count Small complex snags 17 9 11 9 14 7 9Count Small simple snags 25 5 17 18 10 11 13Count Snag Pile 6 1 3 9 2 7 1Count Large complex rocks 9 2 0 2 8 0 0Count Large simple rocks 8 4 0 0 3 1 2Count small complex rocks 11 14 0 0 0 0 2Count small simple rocks 7 3 0 0 0 0 2Count Willow 8 2 22 71 12 88 44Total length in m Erosion (length m) 13.0386 32.1089 124.2849 56.0465 175.2277 367.8056 42.2203Total length in m Undercut (length) 23.4985 0 0 0 0 0 0Area in m2 Typha 0.0003 0 0 0.0015 0.9131 0 0Area in m2 Phragmites australis 0.0124 0 0.0004 0 0 0.0121 0.015Area in m2 Cyperus eragrostis 0 0 0.0042 0 0 0 0Area in m2 Juncus usitatus 0.0012 0.0002 0.0001 0 0 0 0Area in m2 Schoenoplectus validus 0.0003 0 0 0.0002 0 0.0003 0Area in m2 Narrow-leaved emergent

macrophytes0.0142 0.0002 0.0047 0.0017 0.9131 0.0124 0.015

Largest value in reach

Maximum depth (m) 2.5 4 2.5 1.6 2 2.2 2.2

ML/Day Average Daily flow 50 50 50 50 50 50 50Area in ha Dry (ha) 0 0 0 0 0 0 0Area in ha Pool (ha) 0.8109 0.4772 2.0569 0.6367 1.0611 0.765 1.0949Area in ha Rapid (ha) 0.1061 0.0531 0.052 0.0286 0.0091 0.0593 0.0469Area in ha Riffle (ha) 0.224 0.2625 0.2362 0.3593 0.1002 0.2075 0.0398Area in ha Run (ha) 0.8987 2.0806 0.4158 0.6522 0.5734 0.8004 0.7127Area in ha Bedrock (ha) 0.3104 0.0987 0 0 0 0.0152 0Area in ha Boulder (ha) 0.1733 0.1212 0 0.0508 0.0072 0.036 0.0351Area in ha Clay (ha) 0 0 0 0 0 0 0Area in ha Cobble (ha) 0.9268 2.0127 0.9604 0.6195 0.4053 0.987 0.6843Area in ha Detritus(ha) 0 0.0061 0.0059 0 0 0 0Area in ha Gravel (ha) 0.3906 0.467 0.7036 0.9601 1.3313 0.794 1.0582Area in ha Mud (ha) 0 0 0.3638 0.0464 0 0 0.1167Area in ha Sand (ha) 0.3906 0.1676 0.7273 0 0 0 0 * This shows macrophyte species before pooling as per Table 2. Table 5. Results of discriminant function analysis showing the probability that catfish should occur at a site based on the aquatic habitat surveys. Site Probability of catfish presence Broadwater 0.90 Bates Place 0.94 Mavis Place 0.68 Kootingal Bridge 0.66 Newhaven Park 0.55 Riverdene 0.46 Nemingha Bridge 0.78

NSW DPI 15


4. DISCUSSION

Freshwater catfish were distributed along the entire study area of the Cockburn River, being found at all but one of the sites (Bates Place). This is somewhat surprising because Bates Place was judged to be the most optimal with respect to catfish habitat. The site had the deepest maximum depth and this has specifically been shown in NSW inland catfish habitat reference models to be a good predictor of catfish presence (Rourke, Gilligan and Robinson, unpublished). The reason for this may be associated with a greater permanency of deeper habitats during prolonged drought (Balcombe et al. 2006). Longitudinal gradient studies of fish communities in rivers typically show that fish abundance is positively related to depth (e.g. Gelwick 1990). The fact that Bates place was characterised by a smaller abundance of most species may reflect the variable nature of fish community surveys through time and demonstrating that this kind of data is best interpreted using temporally replicated surveys. The wide distribution of catfish throughout the Cockburn River was predicted by the State wide habitat reference models. These predicted that catfish should be commonly found at most sites. The only site where catfish were predicted to occur less than 50% of the time was Riverdene. However, considering that the highest abundance of catfish were found at this site, it is clear that the habitat is sufficient to support catfish, even if it may be viewed as less than optimal relative to State wide reference models. Therefore it would appear that habitat within the Cockburn River is generally in good condition to support a viable catfish population. Size and age-class structure can provide important insights into the status of a fish population (Pope and Willis 1996). An absence of an age-cohort may suggest a poor recruitment season in previous years. This may be particularly the case for freshwater catfish, where immigration and emigration may be minimal because they do not disperse widely (Reynolds 1983). This limited dispersal, when compared to other native species, may reflect the fact that they do not have to offset the downstream drift of their eggs, which are laid in the substrate rather than being buoyant and drifting (Reynolds 1983). The current survey revealed an absence of 200-300 mm fish. Age-size models from nearby river populations (Davis 1977a) suggest these fish may be approximately two years of age, or recruits from the 2008/09 breeding season. Assuming that this reflects a genuine absence of this cohort, it may suggest that conditions were not suitable in the spring and summer of 2008/09 to support successful catfish breeding in the Cockburn River. One can only speculate on the reason for this. The five year hydrograph may suggest that significant floods during this season caused a failure of breeding, potentially through destroying nests and/or washing eggs or larvae downstream. If this is the case, then the most recent breeding season (2010/11) is the first since 2008/09 to experience such severe flooding (Figure 9). Future surveys and analysis of this year’s cohort may shed more light on the validity of this hypothesis. Based on this same reasoning, the dominance of catfish greater than 400 mm or four years of age in the population may suggest that conditions in the breeding season four years and previous to that were suitable to support successful breeding events. We were only able to obtain flow data as far back as five years. This revealed that low, below-average flows dominated in the 2006/07 breeding season. This may suggest that pools in the Cockburn provide important breeding refugia during low-flow conditions. When investigating the link between water abstraction and breeding success, measurements of the variability of flows or fluctuation in water depth at specific sites would be of more consequence than mean monthly river discharge. This is because it is the sudden fluctuation in water depth that

16 NSW DPI


is believed to cause nest abandonment (Lake 1967). Catfish have been observed to abandon nests in the Nymboida River when water levels fall below critical levels within the space of a day in response to the operation of upstream regulators (Gavin Butler, Grafton Fisheries Centre, unpublished data). Whilst it was originally planned to monitor water levels within each of the seven sites throughout the study, significant flooding prevented data logger deployment and would have made data uncharacteristic of typical flow conditions, particularly since abstraction during the study year was not typical of that in an average year (Neal Foster, NSW Office of Water, pers. comm.). Because of these environmental disturbances, it was only possible to make generalisations regarding the catfish population collectively across the seven study sites. Insufficient numbers of catfish caught per site, the large degree of site connectivity during the current study as a result of flooding, and the lack of site-specific depth data means that at this stage it is not possible to determine if any site-specific differences in population structure exist and whether this is in any way associated with fluctuating water level within sites or due to abstraction pressure. To better assess the link between water level and site-scale population differences, catfish sampling will need to be replicated over more years, Similarly, depth data will need to be collected over multiple years to better ascertain the relative impact of groundwater abstraction on pool depth relative to background variability resulting from flow pulses and flooding. It should be acknowledged that sampling bias can result in incorrect interpretation of size and age-class attributes (Pope and Willis 1996), particularly if a certain sampling method targets a particular size-class in greater proportion than the true proportion in the population. Differential behaviour, resulting in differential ‘catchability’ can introduce one form of sampling bias. For example, Serns (1985) noted that walleye populations surveyed with fyke nets at the start and end of the breeding season tended to be of a smaller size-class due to the greater activity and abundance of smaller males on the spawning grounds during this time. A similar scenario may have occurred during the spring-summer catfish surveys. Freshwater catfish generally reach sexual maturity between 3-5 years of age in rivers (Davis 1977b). This corresponds with the most dominant size-class surveyed in the Cockburn River and may reflect greater activity of breeding males and females compared to immature individuals during the time of sampling, rather than an absence of these younger individuals. This assumption could be clarified by repeating surveys outside of the breeding season. Follow-up surveys, which sample both within and outside of breeding seasons are strongly recommended as these will reduce any biases which were compounded by the ‘one-off’ nature of this survey and thereby produce more certainty around the presence and absence of particular size-classes from particular pools. It will also enable longer-term patterns in population structure to be distinguished from short-term disturbances that may occur in response to transient disturbance events such as the flooding encountered during the current survey. A population census such as undertaken here will not be sufficient in determining whether a link exists between nest abandonment and water abstraction. To do this a different series of research questions need to be addressed. It was originally planned to run a pilot study testing a variety of different approaches to quantifying nest abandonment, namely, side-scan sonar versus Dual Frequency Identification Sonar (DIDSON) versus visual estimates. After discussions with researchers experienced in the use of these sonar techniques, it became apparent that both would be of limited use in identifying catfish nests and nesting behaviour. Radio tracking is also available to investigate the behaviour of breeding catfish, but radio tracking data can be hard to interpret because it is both extremely invasive and it would be hard to elucidate movements associated with nest occupancy from nest abandonment (Gavin Butler, Grafton Fisheries Centre, pers. comm.). Visual census appears the only suitable method and would need to be conducted when turbidity was low enough to enable a sufficient proportion of nesting habitats to be viewed from a boat or the bank.

NSW DPI 17


A number of separate research objectives have been outlined in Appendix 4. Whilst each is presented separately as they will each provide important information in isolation, it is likely that a combination of all of these would be necessary to best determine the link between water abstraction and nest abandonment in the Cockburn. They involve replicating population estimates, quantifying site-scale water level variability and its link with water abstraction and the availability of catfish nesting habitat. Ultimately a visual census may be the only tool available to try bring all these together with a quantifiable measure of nest occupancy and abandonment.

18 NSW DPI


5. CONCLUSIONS AND RECOMMENDATIONS

In conclusion, based on the evidence of this single survey of catfish in the Cockburn River in the spring-summer of 2010/11, there is little evidence to suggest that there has been prolonged suppression of catfish recruitment in the Cockburn River. There was a wide size-range of fish present and these were distributed throughout the study reach, as generally predicted by the quality of habitat that was present at most sites. The absence of a particular size-class of catfish potentially suggests an absence of a two year old cohort and a failure of fish to recruit to the population from the 2008/09 breeding season. One must caution about over interpreting the data as population studies such as these are open to bias. The ‘one-off’ nature of this survey does compound sampling biases and makes it difficult to draw definitive conclusions about the status of catfish populations, particularly since significant flooding was experience in the river at the time of sampling. This should be acknowledged if the current data are to be used to inform the development of water access rules. This uncertainty can be reduced by follow-up surveys both within and outside of the breeding season and this is recommended. It was an objective of this study to also consider options for future research aimed at quantifying the potential link between nest abandonment and water abstraction. Some of the technological-based techniques for mapping underwater habitat in turbid rivers such as side-scan sonar and DIDSON would be inappropriate for both locating catfish nests and determining their occupancy. Although constrained by turbidity, visual census appears the only reasonable alternative. A number of separate research objectives and methods have been outlined and although each will provide important information in isolation, determining the link between water abstraction and nest abandonment in the Cockburn River will likely require a combination of all of these approaches.

NSW DPI 19


6. REFERENCES

Anon (1997). Australian Code of Electrofishing Practice. Management Publication No. 1. NSW Fisheries, Cronulla.

Balcombe, S. R., Arthington, A. H., Foster, N. D., Thoms, M. C., Wilson, G. A. and Bunn, S. E.

(2006). Fish assemblages of an Australian dryland river: abundance, assemblage structure and recruitment patterns in the Warrego River, Murray–Darling Basin. Marine and Freshwater Research 57: 619-633.

Cadwallader, P. L. and Backhouse, G. N. (1983) A guide to the freshwater fish of Victoria.

Victorian Government Printing Office, Melbourne. Clunie, P. and Koehn, J. D. (2001). Freshwater catfish: A recovery plan. Final report for Natural

Resource Management Strategy Project 7 R7002 to the Murray Darling Basin Commission. Department of Natural Resources and Environment, Heidelberg.

Cook, P., Lamontagne, S., Berhane, D. and Clark, J. (2006). Quantifying groundwater discharge to

Cockburn River, southeastern Australia, using dissolved gas tracers 222Rn and SF6. Water resources research 42: W10411.

Davis, T. L. O. (1977a). Age determination and growth of the freshwater catfish, Tandanus

tandanus Mitchell, in the Gwydir River, Australia. Australian Journal of Marine and Freshwater Research 28: 119-137.

Davis, T. L. O. (1977b). Reproductive biology of the freshwater catfish, Tandanus tandanus

Mitchell, in the Gwydir River, Australia II. Gonadal cycle and fecundity. Australian Journal of Marine and Freshwater Research 28: 159-69.

FSC (2008). Final determination for Tandanus tandanus. Fisheries Scientific Committee. Industry

and Investment NSW, Nelson Bay. Gelwick, F. P. (1990). Longitudinal and temporal comparisons of riffle and pool fish assemblages

in a northeastern Oklahoma Ozark stream. Copeia 1990: 1072-1082. Harris, J. H. and Gehrke, P. C. (eds) (1997) Fish and rivers in stress: the NSW Rivers Survey. NSW

Fisheries Office of Conservation and CRC for freshwater Ecology, Sydney. Lake, J. S. (1967). Rearing experiments with five species of Australian freshwater fishes. I.

Inducement to spawning. Australian Journal of Marine and Freshwater Research 18: 137-153.

Pope, K. L. and Willis, D. W. (1996). Seasonal influences on freshwater fisheries sampling data.

Nebraska Cooperative Fish & Wildlife Research Unit - Staff Publications. 64. Reynolds, L. F. (1983). Migration patterns of five fish species in the Murray- Darling River

system. Australian Journal of Marine & Freshwater Research 34: 857-872. Serns, S. L. (1985). Proportional stock density index - is it a useful tool for assessing fish

populations in northern latitudes? Research Report No. 132. Department of Natural Resources, Madison, WI.

20 NSW DPI


Snyder, D. E. (2003). Invited overview: conclusions from a review of electrofishing and its harmful effects on fish. Reviews in Fish Biology and Fisheries 13: 445-453.

NSW DPI 21


7. APPENDICES

7.1. Appendix 1 – Site photos

22 NSW DPI


Nemingah Bridge looking upstream.

Riverdene looking upstream

NSW DPI 23


Newhaven Park looking upstream.

Kootingal Bridge looking downstream.

24 NSW DPI


Mavis Place looking upstream.

Bates place looking upstream.

NSW DPI 25


Broadwater looking downstream.

26 NSW DPI


7.2. Appendix 2 – Sites and habitat variables used in inland NSW catfish habitat reference models

(source: Rourke, Gilligan, Robinson, unpublished) Table A2.1. Sites used in the inland NSW catfish habitat reference models.

Category Waterbody name Latitude Longitude Breeding Gwydir River -29.8434416 150.524238 Breeding Cockburn River -31.0606299 151.138695 Breeding Tenterfield Creek -29.0311789 151.724585 Breeding Imperial Lake -31.9463019 141.495296 Breeding Severn River -28.7517881 151.835698 Breeding Lachlan River -33.3424 145.83774 Breeding Castlereagh River -31.44841 149.31784 Breeding Quart Pot Creek -28.66726 151.94753 Breeding Swan Brook -29.74331 151.18874 Breeding Washpen Creek -34.576 142.874 Breeding Macintyre River -29.761 151.12 Breeding Widgiewar Lagoon -35.073 146.283 Present Little River -32.6118589 148.687274 Present Horton River -29.8976395 150.342767 Present Namoi River -30.9761866 150.424288 Present Namoi River -30.2330136 149.622804 Present Murray River -34.1244119 142.03566 Present Island Creek -33.22642 147.3326 Present Macquarie River -32.24511 148.29984 Present Ewenmar Creek -31.78962 148.13155 Present Georges Creek -30.21713 151.2429 Present Tycannah Creek -29.70192 150.09497 Present Tenterfield Creek -28.9417 151.59901 Present Severn River -29.38995 151.17115 Present Bogan River -31.6243722 147.18046 Disappeared Darling River -31.8425357 143.145273 Disappeared Edward River -35.6015976 144.993197 Disappeared Bogan River -30.2617278 146.7413 Disappeared Murray River -34.0516787 141.044424 Disappeared Darling River -30.0873 145.93537 Disappeared Murrumbidgee River -34.7699558 146.573957 Disappeared Barwon River -30.0146298 148.059377 Disappeared Warrego River -29.0891099 145.770986 Disappeared Dumaresq River -28.867556 151.163149 Disappeared Macintyre River -28.7003165 150.530502 Disappeared Lachlan River -33.40318 148.0167

NSW DPI 27


Table A2.2. Habitat variables considered in the inland NSW reference models after merging and deletion, showing transformations applied and the variables considered to best explain the presence/absence of catfish. Variable name Transformation applied Used in final reference

model Altitude Square root Yes Large complex snags Square root No Large simple snags Log10 No Small complex snags Square root Yes Small simple snags Square root No Snag Pile Square root No Erosion (length m) Log10 Yes Emergent macrophytes Square root Yes Submerged macrophytes Log10 No 100m Riparian vegetation cover (ha) No 10m Riparian vegetation cover (ha) No Maximum depth (m) Yes Average Daily flow 4th root No Pool (ha) Log10 No Riffle-Rapid (ha) Log10 No Run (ha) Log10 No Bedrock-Boulder (ha) Log10 Yes Cobble-Gravel (ha) Log10 Yes Mud (ha) Log10 No

28 NSW DPI


7.3. Appendix 3 - Habitat maps of study sites

NSW DPI 29


30 NSW DPI


NSW DPI 31


32 NSW DPI


NSW DPI 33


34 NSW DPI


NSW DPI 35


36 NSW DPI


NSW DPI 37


38 NSW DPI


NSW DPI 39


40 NSW DPI


NSW DPI 41


Cockburn River catfish survey 42

7.4. Appendix 4 – Proposed future research options

Objective Method Resources approximate cost 1. Obtain greater temporal replication of fish surveys to achieve greater certainty with respect to the structure of catfish populations

Biannual fish sampling at 7 sites (once within and once outside of breeding season) for 2 years.

2 staff four weeks sampling annually for 2 years ($37K/year which includes associated travel and operating costs); 1 Research scientist 15 days/year to project manage and analyses and report ($11K/year). Total cost for 2.3 year study = $96K

2. Determine site-specific differences in water level fluctuation and abstraction pressure and associate this with site-scale differences in catfish population structure over a number of breeding and non-breeding seasons

Deploy data loggers for a minimum of 2 years (two breeding, two non-breeding seasons); Associate depth data with site-specific information on abstraction pressure and fish survey data collected as part of objective 1.

7 hydrolab depth loggers deployed for 2 years ($15K); Staff costs to deploy, retrieve and analyses data ($30K). Total for 2.3 year study (excluding fish work covered in objective 1) = $45K

3. Quantify relative area of nesting habitat and determine how this fluctuates with fluctuating water level and abstraction each site.

Undertake detailed bathymetric surveys with doppler and undertake substrate mapping to quantify relative area of nesting habitat; This would need to be done in conjunction with the data collection and analyses carried out in objective 2.

Bathymetric surveys two weeks fieldwork and 1 month analyses (including staffing and operating) = $30K; Detailed surveying of nesting habitat 1months fieldwork (including staffing and operating) = $35K; Research scientist 3 months to analyse and correlate datasets from objective 1 and 2 = $66K; Total cost for 2.3 year study (excluding water level work covered in objective 2) = $131K

4. Quantify rate of nest occupancy at the site scale and relate this with fluctuating water level in each site.

Visual census of nest occupancy at seven sites using visual census. Minimum of fortnightly field trips between November and January for 2 breeding seasons; This would need to be done in conjunction with the data collection and analyses carried out in objective 2.

2 staff, six weeks per year for two years for field work ($50K/year) including associated salary, travel and operating costs). 1 Research scientist 15 days/year to project manage and analyses and report ($11K/year). Total cost for 2.3 year study (excluding water level work covered in objective 2) = $122K

Other titles in the series 43


Other titles in this series: ISSN 1440-3544 No. 1 Andrew, N.L., Graham, K.J., Hodgson, K.E. and Gordon, G.N.G., 1998. Changes after 20 years in relative

abundance and size composition of commercial fishes caught during fishery independent surveys on SEF trawl grounds. Final Report to Fisheries Research and Development Corporation. Project no. 96/139.

No. 2

Status of freshwater catfish populations and their habitat within the Cockburn River

Documents

Transcript of Status of freshwater catfish populations and their habitat within the Cockburn River