ELSEVIER Aquaculture 148 (1997) I79- I90

Effects of initial weight and genetic strain on feed training largemouth bass Micropterus salmoides using ground fish flesh and freeze dried krill as

starter diets

Fernando Kubitza a, Leonard L. Lovshin bp*

a ESALQ-USP/DZ, Au. Pridua Dias. II, Piracicaha, SP, 13418-900, Brazil

b Department of Fisheries and Allied Aquacultures, Auburn University, Auburn, AL 36849, USA

Accepted 25 July 1996

Abstract

Experiment 1 compared the feed training success of two genetic strains of largemouth bass (LMB). ASF strain had 69% northern and 3 1% Florida LMB influence, while STATION strain had 35% northern and 65% Florida LMB influence. Both strains were fed ground fish flesh, freeze dried krill (FDK), a commercial moist pellet (BIODIETTM) or a dry pellet with 70% krill meal (KM-70) as starter diets. In experiment 2, fish of 0.6, 0.9 and 1.4 g or 0.2, 0.4, 0.6, 0.9, and 1.4 g initial weight were feed trained using ground fish flesh or FDK, respectively. In both experiments, fish were weaned from the starter diets to a 2 mm trout pellet using gradual feed ingredient transition (GFIT) with diets containing 80, 60, 40, 20, and 0% ground fish or 70, 50, 30, 10, and 0% krill meal. Percent fish feeding on trout pellets (feeders) among ASF bass was 32% and among STATION fish 34% (P > 0.10). Average percent feeders were 58% and 53% starting bass on FDK and ground fish, respectively, compared to only 14% feeders for bass started on KM-70 and 8% feeders among bass started on BIODIETTM (P < 0.01). In experiment 2, percent feeders increased from 7 to 52% (P < 0.01) as initial fish weight increased from 0.2 to 1.4 g for fish started on FDK. Percent feeders increased from 59 to 88% (P < 0.01) as initial fish weight increased from 0.9 to 1.4 g among fish started on ground fish. Average percent feeders was 75% when ground fish was the starter diet compared to 41% for FDK with 0.9 to 1.4 g fish (P < 0.011.

Keywords: Techniques-culture methods; Techniques-feeding and nutrition; New feeds; Larval rearing; Krill meal; Largemouth bass

* Correspondence author. Auburn University, Dep. of Fisheries and Allied Aquacultures, Auburn, AL

36849. USA.

0044-8486/97/$17.00 Copyright 0 1997 Elsevier Science B.V. All rights reserved.

PIf SOO44-8486(96)0 I4 19-6

180 F. Kubitza, L.L. Lovshin/Aquaculture 148 (1997) 179-190

1. Introduction

Freeze dried krill (FDK) and krill meal (KM) are suitable components in diets to wean 1 g largemouth bass (LMB) from natural food to dry pellets. Seventy-nine to 95% of bass fed FDK accepted it. However, only 50 to 65% of LMB started on FDK

accepted dry pellets after a gradual feed ingredient transition (Kubitza, 1995). Differ- ences in texture between FDK and dry pellets and an apparent genetic influence on the

ability to feed on dry pellets may partially explain the 30 to 45% difference between percent fish feeding on FDK and on a final dry pellet (Kubitza, 1995).

Genetic factors seem involved with the ability of LMB to accept formulated feeds. Northern LMB were easier to train on moist pellets than Florida LMB (Williamson,

1983; Williamson and Carmichael, 1990). Kubitza (1995) observed that 40% of LMB

trained on FDK but unable to learn to feed on a dry pellet could be retrained on FDK and weaned from FDK to the same dry pellet in a second opportunity. However, bass

retrained on FDK had a poorer weaning from FDK to dry pellets compared to bass trained on FDK once, suggesting the existence of a genetic component controlling the ability of LMB to feed on pellets. Identification of strains that readily accept formulated

feeds would improve the intensive culture of LMB. Identification of alternative starter diets and improvements in feed formulation and

processing are still required and may improve feed training of largemouth bass. Ground fish flesh has been widely used to feed train LMB because of its availability and low

cost. The use of ground fish as starter diet for LMB has been investigated (Snow, 1960, 1963; Lovshin and Rushing, 1989; Sloane, 1993). Vitamin deficiency, risk of introduc- ing diseases, and variable weaning success to dry pellets are potential limiting factors in

feeding ground fish to LMB. Largemouth bass fed actively on ground fish, but few fish weaned from ground fish

to dry pellets using gradual feed transition (Sloane, 1993). Gradual feed transition (GFT) is the progressive replacement of the starter diet with the final diet. Kubitza (1995) observed that gradual feed ingredient transition using diets with krill meal was more effective than GFT during weaning of LMB from FDK to dry pellets. Gradual feed ingredient transition replaces a particular starter diet by a sequence of feeds containing decreasing amounts of the main component of the starter diet. Gradual feed ingredient transition using diets with ground fish may improve the weaning of fish trained on

ground fish to dry pellets. As new starter diets are identified, improvements in the methods to feed train LMB

smaller than 1 g are needed. Training bass smaller than 1 g would reduce losses in nursery ponds due to predation and cannibalism, as well as the length of time LMB have to imprint on live food. Feed training success of LMB fry on formulated diets has been varied. Snow (1960) reported that neither ground fish nor fish roe were suitable training diets for 13 to 19 mm fry. However, carp eggs were accepted by 12 to 20 mm fry (Brandenburg et al., 1979; Brandt et al., 1987), while other diets were not adequate. Williamson and Carmichael (1990) successfully weaned 80 to 96% of 0.3 g LMB directly from live food to a commercial moist pellet. Freeze dried krill as a starter diet followed by GFIT using diets with krill meal was an effective strategy to feed train 1 g

F. Kubim, L.L. Loushin /Aquaculture 148 (19971 179-190 181

LMB (Kubitza, 1995). Training fish smaller than 1 g using this strategy was not attempted.

The present study evaluated the use of ground fish flesh as a potential substitute for FDK and krill meal in diets to wean two genetic strains of LMB from live food to dry pellets using GFIT. Training performance of different size fish was also investigated.

2. Materials and methods

2.1. Experiment I

Largemouth bass (Micropterus salmoides) fingerlings from two strains were submit- ted for electrophoretic analysis to quantify their Florida and northern allele frequencies.

One strain of fish was produced at the Agricultural Experiment Station/Fisheries Unit of Auburn University, Auburn, AL (STATION). The other strain of fish originated from a commercial fish hatchery (American Sport Fish, Montgomery, AL); AFS. STATION

strain had 65 and 35% Florida and northern alleles, respectively. Of 23 STATION fish, 4 were pure Florida, 1 was pure Northern, and 18 were hybrids. ASF strain had

frequencies of 3 1 and 69% Florida and northern alleles, respectively. Of 21 ASF fish, 10 were pure Northern, 2 were pure Florida, and 11 were intergrade hybrids. After harvest, fish were graded and held in net cages for 24 h before stocking into 24 0.0.5-m” net

cages (0.38 m X 0.42 m X 0.31 m). The cages were positioned around the perimeter of a 14 m3 circular tank (4.6 m diameter X 0.8 1 m depth) provided with aeration and enough water flow to replace 5% of the tank volume daily. Net cages were stocked with either 200 STATION or 200 ASF fish. Mean initial weight was 1.01 f 0.02 and 1.03 t_ 0.02 g

for STATION and ASF strains, respectively. Four starter diets were evaluated for both strains: a commercial moist pellet (BIO-

DIETTM, Bioproduct Inc., Warrenton, OR), a dry pellet with 70% krill meal (KM-70)

ground fish flesh (GF), and freeze dried krill (FDK, Argent Laboatories Inc., Redmond, WA). Ground fish flesh was prepared by mixing 98% minced catfish muscle with 2%

vitamin premix. The mixture was extruded using a Hobbart extruder (Hobbart Corp.,

Troy, OH), followed by packaging and storage in a freezer. Small quantities of ground fish were defrosted once a day to feed the fish.

Fish were hand fed the starter diets to satiation, four times a day, during a training period of 7 days. After the training period, percent fish feeding on the starter diets (feeders) was determined. Feeders were visually identified by their larger size and distended abdomen which contrasted with the non-feeders smaller size and emaciated appearance. Feeders were returned to the experimental units and weaned to a 2 mm commercial dry, sinking trout pellet (Purina Trout Chow #4, Purina Mills, Inc., St.

Louis, MO). Unequal stocking densities per treatment were used during weaning because of unequal number of feeders.

Diets with 70, 50, 30 and 10% krill meal (KM) or 80, 60, 40, and 20% ground fish were fed in sequence followed by a dry pellet without ground fish or krill meal (KM-00) in a gradual feed ingredient transition (Table 1) to wean fish from FDK or ground fish, respectively, to the trout pellet. Fish trained on BIODIETTM and KM-70 were also

182 F. Kubitza, L.L. Loushin/Aquaculture 148 (1997) 179-190

Table 1

Sequence of diets containing ground fish flesh (GF) or krill meal (KM) used to wean I g largemouth bass

trained on freeze-dried krill (FDK), ground fish flesh (GF), a commercial moist pellet (BIODIET), or a dry

pellet with 70% krill meal (KM-70) to a dry trout pellet (TP) using gradual feed ingredient transition (GFIT)

Starter diets Weaning diets (days) Days on

GFIT

FDK

GF

KM-70

BIODIET

KM-70 (3 d) KM-50 (3 d) KM-30 (2 d) KM-IO (2 d) KM-00 (2 d) TP (4 d) 16 GF-80 (3 d) GF-60 (3 d) GF-40 (2 d) GF-20 (2 d) GF-00 (2 d) TP (4 d) 16

KM-50 (3 d) KM-30 (3 d) KM-IO (2 d) KM-00 (2 d) TP (6 d) 16 KM-30(3 d) KM-lO(3 d) KM-00(4 d) TP (6 d) 16

weaned to trout pellets using GFIT with pellets containing decreasing amounts of krill

meal as detailed in Table 1. Composition of the weaning diets is shown in Table 2.

Dry pellets with krill meal were made by adding 25% water by weight to the feed ingredients and passing the moist mixture through a Hobbart extruder. After extrusion, pellets (1.8 mm diameter and 4-5 mm length) were sun dried about 3 h, cooled and

stored at room temperature. Moist diets containing ground fish were prepared in the same manner. However, addition of water was not required to extrude diets with ground fish. Diets containing ground fish were packed and stored in a freezer immediately after

extrusion. The diet with 80% ground fish (GF-80) had a paste-like consistency, while other diets with ground fish were moist pellets. After the weaning period, percent feeders and feeders growth were determined. Percent feeders can be used as an indicator of fish survival. Morning (8:OO h) and afternoon (16:00 h) dissolved oxygen and water temperature in the circular tank were monitored daily with a dissolved oxygen meter (YSI model 51 B, Yellow Springs, OH). The average values for morning and afternoon

dissolved oxygen and temperature were 7.7 f 0.7 mg/l and 7.5 + 0.8 mg/l, and 24.7 f 2.5”C and 26.0 f 2.5”C, respectively.

Table 2

Percent composition of the weaning diets containing krill meal (KM) or ground fish flesh (GF) used during

gradual feed ingredient transition

Ingredients KM diets GF diets

Anchovy fish meal

Krill meal

Ground fish flesh

Wheat middlings

Menhaden oil

Gelatin

Vitamin premix a

Moisture (%)

KM-00 KM-10 KM-30 KM-50 KM-70

71.00 66.00 64.00 44.00 19.00

10.00 30.00 50.00 70.00

20.00 15.00 - - ”

5.00 5.00 5.00 5.00 10.00

3.00 3.00 - - -

1 .oo 1.00 1.00 1.00 1.00

8.95 8.96 8.72 9.42 9.93

GF-20 GF-40 GF-60 GF-80

74.00 58.00 38.00 18.00 _

20.00 40.00 60.00 80.00 -

4.00 - - -

2.00 2.00 2.00 2.00

14.42 29.12 43.12 56.95

’ Vitamin (mg kg-’ of premix): ascorbic acid (51300), thiamin mononitrate (1530) riboflavin (1530), niacin

(1530), pyridoxine-HCI (1530). cyanocobalamin (1.53), biotin (1.53), pantothenic acid (1,530), folic acid

(3.06). and PABA (920).

F. Kubitza, L.L. Loushin / Aquaculture 148 (1997) 179-I 90 1x3

2.2. Experiment 2

Largemouth bass (STATION strain) were harvested from rearing ponds, graded into different size groups, and stocked into 24 0.05m3 net cages located in a 14 m3 circular tank, as described in experiment 1. Each net-cage was stocked with 200 fish. Fish with initial weights of 0.2, 0.4, 0.6, 0.9 and 1.4 g, or 0.6, 0.9, and 1.4 g were feed trained using FDK or GF, respectively.

Freeze dried krill and ground fish flesh were used as starter diets. Diets with

decreasing levels of krill meal or ground fish were used during the gradual feed

ingredient transition to wean fish trained on FDK or ground fish to a commercial trout pellet. Composition and preparation of the weaning diets was similar to that used in experiment 1 (Table 2). A modification in the preparation of GF-80 resulted in a pelleted

rather than a paste-like diet. To pelletize GF-80, fish meal, ground fish and vitamin premix were blended together and the mixture was refrigerated, almost frozen. The

refrigerated mixture was extruded and pellets were obtained by immediately placing the

“spaghetti-like” threads leaving the extruder inside a plastic, cylindrical container and shaking the container in a circular motion, The pellets obtained were immediately frozen.

Fish were hand fed to satiation four times a day for 6 days. After the training period, percent feeders was determined. Contrary to experiment 1, feeders and non-feeders were returned to the net-cages for a 16-day weaning period. The gradual feed ingredient transition used to wean fish from FDK or GF to trout pellets is detailed in Table 3. At the end of the weaning period, percent feeders, feeders growth and total losses due

cannibalism were determined. The average values for morning and afternoon dissolved oxygen and water temperature were 7.3 f 0.4 mg/l and 6.8 f 0.5 mg/l. and 25.2 f 1.2”C and 26.3 _t 1.8”C, respectively.

2.3. Experimental design and statistical analyses

Experiment 1 was set as a completely randomized design in a 2 X 4 factorial arrangement. Two fish strains and four training diets were the variables tested. Experi-

ment 2 used a completely randomized design in a 2 X 3 factorial arrangement. Two starter diets (FDK and GF) were evaluated at three initial fish weights (0.6, 0.9 and 1.4

g). Freeze dried krill was also used to train 0.2 and 0.4 g LMB. In both experiments treatments were replicated 3 times. Data were submitted to two-way analyses of variance to test for interactions and direct effects of strain and starter diets in experiment 1 or

Table 3

Sequence of weaning diets containing ground fish flesh (GF) or krill meal (KM) used to wean largemouth bass

trained on freeze dried krill (FDK) or ground fish flesh (GF) to a dry trout pellet (TP) using gradual feed

ingredient transition (GFIT)

Starter diets Weaning diets (days) Days on

GFIT

FDK

GF

KM-70 (4 d) KM-50 (3 d) KM-30 (3 d) KM-IO(2 d) TP(4d) 16

GF-80 (4 d) GF-60 (3 d) GF-40 (3 d) GF-20 (2 d) TP(4d) 16

184 F. Kubitza, L.L. Lovshin/Aquaculture 148 (1997) 179-190

initial fish weights and starter diets in experiment 2. Treatment means from experiment 1 were compared using the LSD test (a = 0.05). Orthogonal polynomials were used to detect linear or quadratic effects of initial fish weight on percent feeders and cannibal- ism. Data on percent feeders and cannibalism were transformed using arcsine of the

square root transformation (Steel and Torrie, 1980). Covariance analyses using stocking rate as a covariate were performed on data from the weaning period. Statistical analyses were done using the procedures GLM and BEG of the Statistical Analysis System (SAS

Institute, 1985).

3. Results

3.1. Experiment 1

3.1.1. Acceptance of starter diets Percent feeders for ASF and STATION strains were 47 vs. 50% and not significantly

different (P > 0.10) respectively (Table 4). Percent feeders on FDK (86%), on ground fish (72%) on KM-70 (21%) and on BIODIETTM (16%) were significantly different from each other (P < 0.05). Percent feeders on KM-70 was higher than on BIODIETTM (P < 0.05). No difference (P > 0.10) was found in percent feeders between STATION

and ASF fish trained on FDK ,(85 vs. 86%, respectively) and BIODIETTM (15 vs.16%, respectively). However, difference (P < 0.05) was found for percent feeders between STATION and ASF fish trained on ground fish (82 vs. 61%, respectively) and KM-70

(17 vs. 25%, respectively).

3.1.2. Weaning from starter to final diet Thirty-two percent of the ASF and 34% of the STATION fish that began the study

were feeding on trout pellets by the end of the experiment (P > 0.10) (Table 4).

Table 4

Performance of !argemouth bass from two genetic strains (STATION and ASF) feed trained for 7 days on

freeze dried krill (FDK), ground fish flesh (GF), a dry pellet with 70% krill meal (KM-701 or a moist pellet

(BIODIET), and weaned to a dry trout pellet during a 16-d gradual feed ingredient transition

Initial fish Feeders on the Feeders on Feeders growth Feeders mean (n)

wt. (gl starter diets (%) trout pellets (%) (mg day-‘) wt. Cgl

Fish strains a

STATION 1.01 49.9 34.1 111 3.56 12

ASF 1.03 * 47.1 32.4 134 * * 4.12 * * 12 Starter diets b

BIODIET 1.01 15.5 d 8.4 d 122 3.81 6

KM-70 1.02 21.2 c 14.3 c 119 3.77 6

GF 1.02 71.6 b 52.5 b 129 3.98 6

FDK 1.03 85.7 a 57.8 a 120 3.79 6

sem b 0.0068 1.6239 1.1546 3.5027 0.08 18

a Asterisk in a column indicates a significant difference (ANOVA; * P < 0.05; * * P < 0.01).

b Pooled standard error of diet means (n = 6 and 16 degrees of freedom in the experimental error). Diet

means in the same column not sharing a common letter are significantly different (LSD; P < 0.05).

F. Kubitzu, L.L. Loushin /Ayuuculrure 148 (I 9971 179-I 90 185

Table 5

Growth, percent feeders and cannibalism (CANNIB) among Iargemouth bass of different initial weights

(INIWT) trained for 7 days on freeze dried krill (FDK) or ground fish flesh (GF) and weaned to a dry trout

pellet during a 16-d gradual feed ingredient transition

Starter INIWT Feeders on the Feeders on trout Feeders mean Feeders growth CANNIB n

diets (g) starter diets (%I pellets (%) wt. (g) (mg day-‘) (%)

FDK a 0.17 22.2

0.40 30.7

0.60 51.5

0.93 70.3

1.38 77.5

GF ” 0.60 79.2

0.93 86. I 1.41 85.4

Diet means ’

FDK 0.97 66.4

GF 0.98 83.5 * *

sem ’ 0.0042 1.128.5

6.6 0.69 22 17.5 3

18.8 0.76 1s 4.6 3

30.6 1.38 33 4.1 3

40.1 2.1s 51 4.7 3

51.9 3.17 74 2.1 3

59.2 1.49 37 2.3 3

78.6 2.45 63 2.2 3

87.7 3.43 84 0.2 3

40.9 2.23 53 3.7 * 9

75.2 * * 2.46 * 61 * 1.6 9

0.6134 0.0566 2.3483 0.7040

a Percent feeders on FDK (Y > was quadratically related to INIWT (X1 ( Y = 3.48 +96.784X - 30.66 17X’ ; R* = 0.95; P < 0.01). Percent feeders on trout pellets (Y> was quadratically related to INIWT (X) (Y =

- 3.83 + 65.772 X - 18.5548 X *; R* = 0.99; P < 0.01). Cannibalism (Y) was negatively related to INIWT

!X, (Y = 13.14-9.372X; R* = 0.36; P < 0.01).

Percent feeders on trout pellets was quadratically related to INIWT (X) (Y = - 2.16+ 131.699X -

48.2221 X2; R’ = 0.94; P < 0.01).

’ Diet means for 0.6, 0.9 and 1.4 g fish. Pooled standard error of diet mean (n = 6 and 16 degrees of freedom

in the experimental error). Asterisk in the same column indicate a significant difference (ANOVA, ’ P < 0.05:

** P<O.Ol).

Fifty-eight percent of bass started on FDK and 52% of bass started on ground fish were

feeding on trout pellets by the end of the experiment (P < 0.05). These values were higher than the 14 or 8% feeders on trout pellets when bass were started on KM-70 or BIODIETTM, respectively (P < 0.05). Percent feeders on trout pellets was higher

starting fish on KM-70 than on BIODIETTM (P < 0.05). Percent feeders on trout pellets was 59% for ASF and 56% for STATION strains

when FDK was the starter diet (P > 0.05). Statistical differences in the ability of ASF and STATION fish to accept trout pellets were observed feeding BIODIETTM (11 vs. 6%, respectively), KM-70 (20 vs. 9%, respectively) or ground fish (39 vs. 66%, respectively) as starter diets (P < 0.05). ASF feeders had a mean growth and harvest weight of 134 mg/day and 4.1 g compared to 111 mg/day and 3.6 g, respectively, for STATION feeders (P < 0.01). Feeders growth and mean weight were not affected by the

starter diets (P > 0.05).

3.2. Experiment 2

Percent feeders on FDK or on ground fish (Table 5) improved with increase in initial fish weight (P < 0.01). An average of 84% of the 0.6 to 1.4 g bass were eating ground fish compared to only 66% eating FDK at the end of the training period (P < 0.01).

186 F. Kubitza, L.L. Loushin/Aquaculture 148 (1997) 179-190

Among LMB started on FDK, percent feeders on trout pellets at the end of the weaning period increased from 7 to 52% as the initial fish weight increased from 0.2 to 1.4 g (P < 0.01) (Table 5). Percent feeders on trout pellets increased from 59 to 88% as the initial weight of fish started on ground fish increased from 0.6 to 1.4 g (P < 0.01). Average percent feeders on trout pellets was 75% using ground fish compared to 41% using FDK as starter diets for LMB with initial weights of 0.6 to 1.4 g (P < 0.01).

Feeders on trout pellets started on ground fish grew faster and had higher mean harvest weight compared to feeders on trout pellets started on FDK (P < 0.05) (Table 5). Cannibalism reduced from 18 to 2% as the initial weight of fish started on FDK

increased from 0.2 to 1.4 g (P < 0.01). Cannibalism among 0.6 to 1.4 g bass trained on

ground fish was 1.6% compared to 3.7% for bass trained on FDK (P < 0.05).

4. Discussion

4.1. Starter diets and training success

Ground fish flesh and FDK were better starter diets than BIODIETTM and KM-70. Percent feeders on FDK among 0.9 to 1 g LMB ranged from 70 to 86% in both

experiments (Tables 4 and 5) and correspond to the 79 to 95% feeders on FDK previously reported for LMB (Kubitza 1995). Ground fish flesh was comparable to FDK as a starter diet for 0.9 to 1 g LMB. Percent feeders on ground fish among 0.9 to 1 g LMB ranged from 72 to 86% in both experiments (Tables 4 and 5). Why the percent feeders on FDK dropped from 86 to 70% for experiments 1 and 2, respectively, while

percent feeders on GF increased from 72 to 86% in not understood. Fish accepted ground fish the first time it was offered at the beginning of the experiment, but several feeding attempts were required before FDK was accepted. Freeze dried krill floats on the

water surface while ground fish slowly sinks. Fish were hesitant to come to the surface to eat the first day of feeding, which may explain why FDK was not promptly accepted.

Snow (1960, 1963, 1968)) was a pioneer in feed training LMB. He used ground fish as a training diet and reported 39 to 97% feeders on ground fish. The broad range in percent feeders on ground fish was likely due to differences in bass sizes initiated on ground fish, experimental methods and enviromental parameters.

Kubitza (1995) observed the low palatability of soybean meal and the feed enhancing effects of krill and fish meal in diets for LMB. Krill meal was also an important dietary ingredient to enhance feeds for other fishes (Allahpichay and Shimizu, 1984; Higgs et al., 1985). In the present study, dry pellets with 70% krill meal (KM-70) were formulated using only animal ingredients &ill meal, fish meal and fish oil) to improve its acceptance by young bass. However, only 17 to 25% of the bass accepted KM-70 during the training period. The poor acceptance of KM-70 as a starter diet for LMB appears more a matter of inadequate texture than flavor. Texture of KM-70, although improved by using higher dietary levels of lish oil, was still not as soft as the texture of ground fish or FDK. Soft texture seems to be an important characteristic in starter diets for LMB, but the acceptance of dry/hard pellets can be increased after a learning experience on soft diets (Lovshin and Rushing, 1989; Kubitza, 1995).

F. Kubitza. L.L. Loushin /Aquaculture 148 (1997) 179-I 90 187

Contrary to KM-70, BIODIETTM has a moist/ soft property but probably lacks

adequate flavor, which may explain its poor acceptance as starter diet for LMB during the training period (Table 4). Some studies found BIODIETTM an effective starter diet for LMB. Lovshin and Rushing (1989) observed 90% feeders among 1.2 g LMB offered BIODIETTM 3 times a day, and 88% of these fish weaned to dry pellets. Williamson and Carmichael (1990) reported 80 to 96% feeders among 0.3 g LMB fed BIODIETTM every 5 minutes. However, recent studies using BIODIETTM were not as successful. Sloane (1993) reported that only 28% of 0.3 g LMB and 47% of 0.8 g LMB weaned to a

dry pellet when fed BIODIET TM 4 times a day. Kubitza (1995) observed that only 9 to

12% of 1 g LMB accepted BIODIETTM as a starter diet when offered the feed 4 times a day. Animal products have been frequently replaced by plant materials in commercial feeds. Some plant materials are usually cheaper protein sources, but they often show

reduced palatability to fish. The poor acceptance of BIODIETTM by LMB in recent

studies at Auburn is hard to explain in view of the past successes documented in other studies. Other factors influencing diet acceptance by LMB are differences in training

environments, initial fish size, genetic strains and feeding strategies.

4.2. Effect of strains on training success

Differences among strains may also be involved with the varied results observed during feed training of LMB. Williamson (1983) reported 43% feeders in a strain with 70% intergrade northern and Florida LMB compared to 24% feeders with a pure northern strain fed BIODIET TM Brandt et al. (1987) fed carp eggs to a Florida-northern . intergrade and northern LMB strains and obtained 81 and 57% feeders, respectively. However, Williamson and Carmichael (1990) obtained 96% feeders with northern compared to 80% for Florida LMB using BIODIETTM as the training diet.

The intergrade fish used by Williamson (1983) and Brandt et al. (1987) originated

from a LMB population that was feed trained for numerous generations by Jack Snow in Marion, AL. Lovshin and Rushing (1989) were able to feed train 88% of these Marion fish to a dry pellet. Possibly, Snow successfully selected a strain with improved ability

to accept formulated feeds. In the present study, ASF (69% northern and 3 1% Florida intergrades) and STATION (35% northern and 65% Florida intergrades) LMB showed comparable acceptance of a trout pellet (Table 4). ASF and STATION fish had never been submitted to feed training in previous generations. Therefore, it may be possible that previous feed training history has a stronger effect on the ability of a strain to accept formulated feeds than its northern or Florida LMB contribution.

4.3. Weaning from starter to final diet

Among the 0.9 to 1 g fish used in both experiments of this study, 64 to 91% of the feeders on ground fish, 57 to 79% of the feeders on FDK, 40 to 69% of the feeders on BIODIETTM and 52 to 8 1% of the feeders on KM-70 weaned to trout pellets after GFIT.

Sudden change in dietary texture and flavor seems to be the major factor limiting the weaning of LMB from ground fish or FDK to a dry pellet. Sloane (1993) reported that among 0.8 g fish started on ground fish, followed by a diet sequence in which dry

188 F. Kubitza, L.L. Loushin/Aquaculture 148 (1997) 179-190

pellets progressively replaced ground fish in a gradual feed transition (GFT), only 11% accepted dry pellets. However, 54% of LMB started on ground fish learned to feed on a dry pellet by teaching the bass to accept a combination of ground fish and a moist pellet in GFT and, then, replacing the moist pellet with the dry pellet in GFT. Freeze dried

krill was also an attractive starter diet for largemouth bass, but only 13 to 28% of bass started on FDK accepted a dry pellet (Sloane, 1993; Kubitza, 1995). Kubitza (1995) reported up to 65% feeders among largemouth bass trained on FDK and weaned to a dry

pellet using gradual feed ingredient transition (GFIT). Gradual feed transition from FDK or ground fish to a dry pellet does not seem an

appropriate weaning strategy, since GFT allows feed selection, which favors the most

aggressive fish. The practice of mixing FDK or ground fish with dry pellets has provided mixed results since LMB ingest the FDK and ground fish and reject the pellets. Another procedure with little benefit during GFT is to feed the dry pellets first, leaving

the FDK or ground fish last. Fish wait for the more palatable dietary item, leaving the

dry pellets untouched. In the present study, the use of GFIT overcame many of the problems associated with

the weaning of LMB from ground fish or FDK to a dry pellet. Dietary components are presented in a pelleted form during GFIT, suppressing feed selectivity. During GFIT, texture and flavor of the weaning diets were gradually altered as ground fish or krill meal were progressively replaced by fish meal and other feed ingredients. Changes in texture were less drastic during GFIT from ground fish compared to FDK. Pellets with ground fish were moist and had a texture as soft as the ground fish, while pellets with

krill meal were not as soft as FDK. This may explain why 73 to 90% of the feeders on ground fish switched to trout pellets compared to only 62 to 68% of the feeders on FDK.

4.4. Fish size and training success

Percent feeders on trout pellets improved as initial fish weight increased, independent of the starter diet used (Table 5). The improvement in percent feeders with the increase in initial fish size was observed during the feed training of several other carnivorous fishes (Anderson, 1974; Nelson et al., 19’74; Flickinger et al., 1975; Bromley, 1978; Willis and Flickinger, 198 1, 1982).

Using either FDK or ground fish in experiment 2, percent feeders on trout pellets was highest among 1.4 g LMB. However, pond production of 1.4 g fingerlings would require lower stocking rates to avoid premature zooplankton depletion and growth stunting compared to production of 0.9 g or smaller fish. In addition, fish mortality due to cannibalism in ponds is more likely to occur when larger fingerlings are produced. Additional information on the economics of producing LMB fingerlings beyond 0.9 to 1 g on natural food is required. Meanwhile, the use of 0.9 to 1.0 g fish for feed training is advisable. Fish as small as 0.6 g were effectively trained to accept trout pellets by feeding ground fish as a starter diet followed by GFIT to trout pellets (Table 5). Feed training of fish smaller than 0.6 g using ground fish was not attempted in the present study, and would be an attractive subject for future research.

Cannibalism decreased as initial fish weight increased (Table 5). Cuff (1977) reported frequent cannibalism among walleyes, Stizostedium uitreum, less than 20 days old even

F. Kubina, L.L. Looshin /Ayuuculture 148 (1997) 179-190 189

in the presence of alternative food items. Larger fish, however, did not attempt to

cannibalize if alternative food was available. Snow (1960, 1963) also observed a reduction in cannibalism among LMB as the fish grew and learned to accept formulated feeds.

4.4.1. Fish growth

Individual growth rates of LMB feeding on pellets at the end of experiment 1 ranged

from I 11 to 134 mg/day and were comparable or even superior to growth rates previously reported using similar fish size and duration of training (Lovshin and

Rushing, 1989; Sloane, 1993; Kubitza, 1995). ASF feeders had superior growth and

mean weight compared with STATION feeders (Table 4) which may be attributed to the greater northern LMB influence in ASF compared with STATION strain. Northern LMB

outgrew Florida LMB in pond trials, feeding either on forage fish (Zolczynski and Davies, 1976) or on moist pellets (Williamson and Carmichael, 1990). Pure northern strains or northern X Florida reciprocal hybrids grew faster than pure Florida LMB

during feed training (Williamson and Carmichael, 1990). There were no differences in growth of feeders in experiment 1 attributed to starter

diets. However, in experiment 2 feeders started on ground fish had faster growth than

feeders started on FDK (Table 5). Ground fish flesh was promptly accepted by LMB,

while FDK required at least one day before it was readily accepted. Earlier acceptance of ground fish may have given an initial advantage to LMB trained on ground fish compared to FDK. Ground fish flesh was also supplemented with a vitamin premix,

while FDK was not. Levels of thiamin (2-4 mg/kg), riboflavin (l-2 mg/kg), pantothenic acid (6-9 mg/kg), and biotin (< 0.1 mg/kg) in krill as compiled by

Storebakken (1988), barely meet the requirements of salmonids (NRC, 1993). Sloane

(1993) observed high mortality among 0.35 g LMB trained on FDK, which could be partially caused by a deficiency in ascorbic acid. Kubitza (1995) found that supplement-

ing FDK with vitamins, inc!uding ascorbic acid, did not enhance survival of 1 g LMB compared to 1 g LMB fed unsupplemented FDK, although growth rate was slightly improved.

Acknowledgements

The authors are indebted to Mr. Charles Wright (State Hatchery of Meridian, Meridian, MS, USA) and Mr. Don C. Keller and Mr. Barry W. Smith (American Sport Fish, Montgomery, AL, USA) for providing part of the experimental fish used in this study. Thanks are also due to Dr. John C. Williams (Professor, Auburn University,

Auburn, AL) for the valuable suggestions on the statistical analyses and to Mr. Eduardo A. Ono, graduate student of the Department of Fisheries, Auburn University, for the valuable support in field activities.

References

Allahpichay, I. and Shimizu, C., 1984. Supplemental effect of the whole body krill meal and the eon-muscle

krill meal of Euphasia superba in fish diet. Bull. Jpn. Sot. Sci. Fish., 50: 815-820.

190 F. Kubitza. L.L. Loushin /Aquaculture 148 (1997) 179-I 90

Anderson, R.J., 1974. Feeding artificial diets to smallmouth bass. Prog. Fish-Cult., 36: 145-151.

Brandenburg, A.M., Ray, MS. and Lewis, W.M., 1979. Use of carp eggs as a feed for fingerling largemouth

bass. Prog. Fish-Cult., 41: 97-98.

Brandt, T.M., Jones Jr., R.M. and Anderson, R.J., 1987. Evaluation of prepared feeds and attractants for

largemouth bass fry. Prog. Fish-Cult., 49: 198-203.

Bromley, P.J., 1978. The weaning of hatchery reared turbot larvae (Scophthalmus maxims L.) on a dry diet.

Aquaculture, 13: 339-345.

Cuff, W.R., 1977. Initiation and control of cannibalism in larval walleyes. Prog. Fish-Cult., 39: 29-32.

Flickinger, S.A., Anderson, R.J. and Puttmann, S.J., 1975. Intensive culture of smallmouth bass. In: R. H.

Stroud and H. Clepper (Editors). Black bass biology and management. National Symposium on the

Biology and Management of the Centrarchid Basses, Tulsa, OK, pp. 373-379.

Higgs, D.A., Markert, J.R., Plotnikoff, M.D., McBride, J.R. and Dosanjh, B.S., 1985. Development of

nutritional and environmental strategies for maximizing the growth and survival of juvenile pink salmon

(Oncorhynchus gorbuscha). Aquaculture, 47: 113-130.

Kubitza, F., 1995. Intensive culture of largemouth bass: production of advanced juveniles and food size fish.

Ph.D. Dissertation, Auburn University, Auburn, AL, 145~.

Lovshin, L.L. and Rushing, J.H., 1989. Acceptance by largemouth bass fingerlings of pelleted feeds with a

gustatory additive. Prog. Fish-Cult., 51: 73-78.

Nelson, J.T., Bowker, R.G. and Robinson, J.D., 1974. Rearing pellet-fed largemouth bass in a raceway. Prog.

Fish-Cult., 36: 108- 110.

NRC, 1993. Nutrient Requirements of Fish. National Academy Press, Washington, DC 114 pp.

SAS Institute, 1985. SAS/STAT guide for personal computers, version 6 edition. SAS Institute, Lary, NC.

Sloane. M.B., 1993. Performance of training and grow-out diets for largemouth bass. M.S. Thesis. Auburn

University, Auburn, AL, USA, 66~.

Snow, J.R., 1960. An exploratory attempt to rear largemouth black bass fingerlings in a controlled environ-

ment, In: Proceedings of the 14” Annual Meeting of the Southeastern Association of Game and Fish

Commissioners., Biloxi, MS, pp. 253-257.

Snow, J.R., 1963. Results of further experiments on rearing largemouth bass fingerlings under controlled

conditions. In: Proceedings of the 17” Annual Conference of the Southeastern Association of Game and

Fish Commissioners. Hot Springs, AR, pp. 191-203.

Snow, J.R., 1968. The Oregon moist pellet as a diet for largemouth bass. Prog. Fish-Cult., 30: 235.

Steel, R.G.D. and Torrie, J.H., 1980. Principles and Procedures of Statistics: a Biometrical Approach. 2.ed.

McGraw-Hill, New York. pp. 48 I

Storebakken, T., 1988. Krill as a potential feed source for salmonids. Aquaculture, 70: 193-205.

Williamson, J.H., 1983. Comparing of training success of two strains of largemouth bass. Prog. Fish-Cult., 45:

3-7.

Williamson, J.H. and Camtichael, G.J., 1990. An aquacultural evaluation of Florida, northern and hybrid

largemouth bass, Micropferus salmoides. Aquaculture, 85: 247-257.

Willis, D.W. and Flickinger, S.A., 1981. Intensive culture of largemouth bass fry. Trans. Am. Fish. Sot., 1 IO:

650-655.

Willis, D.W. and Flickinger. S.A., 1982. Common carp eggs as a starter diet for the intensive culture of

smallmouth bass fry. Prog. Fish-Cult., 44: 28-29.

Zolczynski Jr., S.J. and Davies, W.D., 1976. Growth characteristics of the northern and Florida subspecies of

largemouth bass and their hybrid. and a comparison of catchability between the subspecies. Trans. Am.

Fish. Sot., 105: 240-243.