MEPS 134:27-35 (1996)  -  doi:10.3354/meps134027

Effect of gut contents and lipid degradation on condition measures in larval fish

Lochmann SE, Maillet GL, Taggart CT, Frank KT

The importance of gut contents to estimates of lipid class composition was evaluated by comparing the lipid composition of gut contents and larval Atlantic cod Gadusmorhua body tissue analyzed separately. Ingested prey accounted for an average of 56% (range = 4 to 95%) of the total lipids from individual larvae. Energy reserves and structural lipids were both influenced by contributions from gut contents. Lipids from prey in the gut biased condition indices based on lipid class composition (triacylglycerol to sterols ratio and triacylglycerol content). A review of studies in the literature, where biochemical measures of condition were assessed, determined that 75% of studies on condition may be biased by prey in the guts. We further investigated the effects of collection and handling protocol on lipid class composition of cod larvae. Triacylglycerol, phospholipids and free fatty acids increased significantly during a simulated collection process. We also examined the effect of time delays between death and preservation on lipid composition. Concentration of free fatty acids, mono- and diacylglycerol increased and triacylglycerol and phospholipids decreased with increasing time between death and preservation. However, the time trend explained only a small portion (2 to 32%) of the overall variability. We suggest studies employing other biochemical measures of condition may also suffer from the variability we identified as being introduced by collection and processing protocols.

Marine larvae . Condition indices . Lipid composition . Degradation . Biochemical measures . Gut contents . Iatroscan TLC-FID . Atlantic cod

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