TY - JOUR

T1 - The utility of carbon and nitrogen isotope analyses to trace contributions from fish farms to the receiving communities of freshwater lakes

T2 - a pilot study in Esthwaite Water, UK

AU - Grey, Jonathan

AU - Waldron, Susan

AU - Hutchinson, Rebecca

PY - 2004/8

Y1 - 2004/8

N2 - A pilot study was conducted to assess the potential for stable isotope analyses to reveal the fate of waste pelleted food material from fish farms in freshwater food webs. Esthwaite Water (Cumbria, UK) was selected as the study site, as it hosts an established salmonid farm, and a wealth of complementary limnological data exists. Salmonid pellet feed consists of primarily marine-derived material and thus exhibits carbon and nitrogen stable isotopic compositions distinct to most freshwater organic material. Comparison of the isotopic ratios of organisms at the cage site with an unaffected control site, supports incorporation of pellet-derived material to the diet of planktonic and benthic communities. Moreover, after allowing for a number of trophic transfers, stable isotope analyses revealed the predatory cladoceran Leptodora kindti also utilised pellet material, while roach were probably short-circuiting the food chain by directly consuming particulate pellet material, as well as via ingestion of their zooplankton prey. Isotope data substituted into a simple two-source mixing model suggested that approximately 65% of Daphnia, and >80% of roach body carbon may be derived from pellet material in the plankton, and that chironomid larvae may incorporate >50% in the sediment environs. However, contributions calculated from both δ 13C and δ 15N values were inconsistent, which may simply be due to the constraints of the model and parameters used, but may also reflect different routing of isotopes from the original pellet source, via soluble or particulate routes.

AB - A pilot study was conducted to assess the potential for stable isotope analyses to reveal the fate of waste pelleted food material from fish farms in freshwater food webs. Esthwaite Water (Cumbria, UK) was selected as the study site, as it hosts an established salmonid farm, and a wealth of complementary limnological data exists. Salmonid pellet feed consists of primarily marine-derived material and thus exhibits carbon and nitrogen stable isotopic compositions distinct to most freshwater organic material. Comparison of the isotopic ratios of organisms at the cage site with an unaffected control site, supports incorporation of pellet-derived material to the diet of planktonic and benthic communities. Moreover, after allowing for a number of trophic transfers, stable isotope analyses revealed the predatory cladoceran Leptodora kindti also utilised pellet material, while roach were probably short-circuiting the food chain by directly consuming particulate pellet material, as well as via ingestion of their zooplankton prey. Isotope data substituted into a simple two-source mixing model suggested that approximately 65% of Daphnia, and >80% of roach body carbon may be derived from pellet material in the plankton, and that chironomid larvae may incorporate >50% in the sediment environs. However, contributions calculated from both δ 13C and δ 15N values were inconsistent, which may simply be due to the constraints of the model and parameters used, but may also reflect different routing of isotopes from the original pellet source, via soluble or particulate routes.

KW - benthos

KW - carbon

KW - fish farms

KW - nitrogen

KW - plankton

KW - stable isotopes

U2 - 10.1023/B:HYDR.0000036144.49795.dd

DO - 10.1023/B:HYDR.0000036144.49795.dd

M3 - Journal article

VL - 524

SP - 253

EP - 262

JO - Hydrobiologia

JF - Hydrobiologia

SN - 0018-8158

IS - 1

ER -