In situ determination of food daily ration in fish: review and field evaluation

Abstract

SynopsisA literature review showed that numerous studies have dealt with the estimation of fish daily ration in the field. Comparisons of results from different studies are often difficult due to the use of different approaches and methods for parameter estimations. The objective of the present study was to compare the most commonly used approaches to estimate fish daily ration and to propose a standardized procedure for their estimation in the field. Comparisons were based on a field experiment specifically designed to investigate these questions and on data and theoretical considerations found in the literature. The results showed that (1) the gut fullness computed with entire digestive tract content is preferable to the stomach content only, supporting recent research done on other fish species; (2) it is important to consider the data distribution before estimating parameters; (3) estimates of experimental evacuation rates should be used rather than maximum evacuation rate for species showing no feeding periodicity; (4) it is necessary to exclude parasites from gut content in the computation of daily ration as they may significantly decrease daily ration estimates (by an average of 29.3% in this study); and (5) the Eggers (1977) model is as appropriate as, and less complex than, the Elliott & Persson (1978) model for estimating fish daily ration in the field, again supporting recent experiments done on other fish species.

Gut evacuation rates in <i>Nephrops norvegicus</i> (L., 1758): laboratory and field estimates

“…At time intervals of 1, 2, 3.5, 5 and 7 hours one group of 10 individuals were sacrificed by immersion in 10% buffered formalin ("serial slaughter method"; Windell, 1967) (Thorpe, 1977;Héroux and Magnan, 1996); 48 hours later, in the laboratory, they were transfered into 70º ethyl-alcohol. The biological sampling analysis included carapace length measurements (to the nearest 0.01 mm), sex determination and stomach removal (preserved in 70º alcohol).…”

“…This method assumes that laboratory conditions, starvation before feeding, and lack of prey diversity may have a limited effect on the evacuation rate (Héroux and Magnan, 1996). According to the same authors, one advantage of this method is that individuals are presumed to be unstressed after acclimatisation and during the experience; it is also possible to control the quantity of food ingested by each individual.…”

“…Determination of R using field experiments has also been carried out for fish (Garcia and Adelman, 1985;Boisclair and Leggett, 1988;Parrish and Margraf, 1990;Héroux and Magnan, 1996). However, in crustaceans, in situ experiments have been limited to non-decapods such as copepods (Kiørboe and Tiselius, 1987;Dam and Peterson,1988), amphipods (Clarke et al, 1988;Perissinotto and Pakhomov, 1996).…”

“…However, in crustaceans, in situ experiments have been limited to non-decapods such as copepods (Kiørboe and Tiselius, 1987;Dam and Peterson,1988), amphipods (Clarke et al, 1988;Perissinotto and Pakhomov, 1996). An alternative method for estimating R is based on the R max procedure (Héroux and Magnan, 1996;Maynou and Cartes, 1998). In field studies it is assumed that the stress due to capture and holding may have negligible effects on the evacuation rate.…”

“…Gut evacuation rates have been mainly determined in fish, during either field or laboratory experiments (Persson, 1979;Jobling, 1980aJobling, , 1980bBrodeur, 1984;Garcia and Adelman, 1985;Brodeur and Pearcy, 1987;Amundsen and Klemetsen, 1988;Héroux and Magnan, 1996). However, the methodologies used for fish have rarely been applied to invertebrates such as decapod crustaceans.…”