Isotopic offset between muscle and scales of three Mediterranean fishes: Dentex dentex, Argyrosomus...

Isotopic offset between muscle and scales of three Mediterranean fishes: Dentex dentex, Argyrosomus regius and Xyrichtys novacula

Andreu BLANCO1*, Salud DEUDERO2, Antonio BOX3

1* Laboratory Biology and Physiology Fish Larvae, Instituto Investigaciones Marinas (CSIC) 2 Centro Oceanográfico de Baleares, Instituto Español de Oceanografía

3 Laboratorio Biologia Marina, Univesidad Illes Balears

Outline • Background • Objective • Materials and methods

• Main results

• Discussion

39th CIESM Congress, Venice (Italy)

Background • Stable Isotopes Analysis Importance - Simple collecting technique - More studies on sampled organisms - Short and long-term diet identification: tissue dependent - Record source and trophic level information


Background • δ13C and δ15N

Trophic Enrichment (Δ): δORGANISM – δDIET δ13C Δ = 1‰ δ15N Δ = 3‰ Isotopic Offset: δTISSUE 1 – δTISSUE 2 Analysing different tissues = timescale to assimilate Stable isotopes and turnover

Consumer 2

Consumer 1

PP


Background • Lethal vs Non-lethal sampling


Objective • Aim: assess, contrast and interpret SI ratios of Dentex dentex,

Argysrosomus regius Xyrichtys novacula.

• Testing the hypotheses: 1) Differences in correlation between muscle and scale 2) Constant isotopic offset in wild and caged fishes


Contribution of the study Increase the non-lethal methods on isotopic studies: - Conservation purposes - Avoid species decrease - Preservation of resources - Maintenance of gene pools


Materials and Methods • Farmed fishes Dentex dentex: TL = 500 - 614 mm W = 2153.7 - 4730.0 g Argyrosomus regius: TL = 420 - 575 mm W = 579.5 - 1400.7g • Wild fishes Xyrichtys novacula: TL = 109 - 184 mm

Ministry of the Environment and Rural and Marine Affairs


Materials and Methods • Stable isotopes - MUSCLE Fish dissection Left side back to the dorsal fin (Kennedy et al 2005)

- SCALES Fish scraping Front left side dorsal to the lateral line (Kennedy et al 2005)

All samples Analysed for SIA by CF-IRMS


Results • δ13C and δ15N muscle-scale: Significant differences (p < 0.01)

for all species Kurtosis (total length distribution):

Dentex dentex k > 0 Argyrosomus regius k < 0.5 Xyrichtys novacula k < 0.5


Results • Dentex dentex: Isotopic offset No relationship Enrichment Δ13C = 3.02 ± 0.06‰ Depletion Δ15N = 0.91 ± 0.14‰

Ministry of the Environment and Rural and Marine Affairs


δ13C and δ15N signif. diff.

Results • Argyrosomus regius: Isotopic offset Signif. relationship Enrichment Δ13C = 2.27 ± 0.07‰ Depletion Δ15N = 1.69 ± 0.06‰



Results • Xyrichtys novacula: Isotopic offset Signif. relationship Enrichment Δ13C = 2.52 ± 0.04‰ Depletion Δ15N = 0.96 ± 0.03‰



Results • Isotopic Offset:

Between species: Signif. diff. (p < 0.05) No signif. diff. between D. dentex and X. novacula (p > 0.05) Between muscle and scales: Signif. diff. (p < 0.001) Exception: Δ13C between A. regius and X. novacula (p > 0.05) Δ15N between D. dentex and X. novacula (p > 0.05)


Discussion • Importance of non-lethal methodolgies

• Scales instead of muscle

• Isotopic dispersion and diet

• Isotopic dispersion and length


Discussion • Correction factor No Dentex dentex (non-correlation values) Yes Argyrosomus regius Xyrichtys novacula Non-lethal methodologies: Decrease impact on bio-ecological studies Catch-and-release: no dead Further studies between lethal and non-lethal tissues

Linear correlation


Acknowledgment • Financially supported by Project JACUMAR (LIMIA, Andratx)

• S. Tejada, J.M. Valencia


Isotopic offset between muscle and scales of three Mediterranean fishes: Dentex dentex, Argyrosomus...

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