Modelling gastric evacuation in gadoids feeding on crustaceans

Abstract

A mechanistic, prey surface-dependent model was expanded to describe the course and rate of gastric evacuation in predatory fishes feeding on crustacean prey with robust exoskeletons. This was accomplished by adding a layer of higher resistance to the digestive processes outside the inner softer parts of a prey cylinder abstraction and splitting up the prey evacuation into two stages: an initial stage where the exoskeleton is cracked and a second where the prey remains are digested and evacuated. The model was parameterized for crustaceans with different levels of armour fed to Atlantic cod Gadus morhua or whiting Merlangius merlangus and recovered from the stomachs at different post-prandial times. The prey species were krill Meganyctiphanes norvegica; shrimps and prawns Crangon crangon, Pandalus borealis, Pandalus montagui and Eualus macilentus; crabs Liocarcinus depurator and Chionoecetes opilio. In accordance with the apparent intraspecific isometric relationship between exoskeleton mass and total body mass, the model described stage duration and rate of evacuation of the crustacean prey independently of meal and prey sizes. The duration of the first stage increased (0-33 h) and the evacuation rate of both stages decreased (by a half) with increasing level of the crustacean armament in terms of chitin and ash. A common, interspecific parameterization of the model within each of the categories krill, shrimp and crab can probably be used if the contents of chitin and ash are similar among prey species per prey category. The model offers a simple way for estimating evacuation rates from stomach content data in order to obtain food consumption rates of wild fishes, provided that information about digestion stage of crustacean prey is available.

Parameterizing an expanded square root model to account for the effects of temperature, meal size, and body size on gastric evacuation rate in farmed brown trout

“…The generic value of the square root model to adequately describe the course of GE independently of meal size has been (3a) dt = −0.00245W 0.41 e 0.06T √ S t (g/h), where W is a total fish weight (g), T is the temperature (°C), and t is time (h). Based on this parameterized GER model, a fish size of 100 g ( ) fed a meal size of 2% body weight at temperature 12°C ( ) required 11.4, 24.9, 42.5, and 85.1 h to evacuate 25%, 50%, 75% and 100% proportions of the meal, respectively [Colour figure can be viewed at wileyonlinelibrary.com] confirmed for various wild fishes, for example saithe Pollachius virens, whiting Merlangius merlangus, and cod Gadus morhua, fed a variety of prey species (Andersen, 1998(Andersen, , 2001Andersen et al, 2016;Temming & Herrmann, 2001), and farmed fish, for example brook trout Salvelinus fontinalis, Russian sturgeon, Acipenser gueldenstaedtii and Siberian sturgeon, A. baerii (Khan et al, 2016;Mazlum & Alabdullah, 2019;Mazlum et al, 2020). This has been supported by the use of a mechanistic cylinder model based upon simple surfacearea considerations of the food or prey that is digested allometrically by continuous peeling off its curved side (Andersen & Beyer, 2005a, 2005b).…”

The forgotten feeding ground: patterns in seasonal and depth‐specific food intake of adult cod Gadus morhua in the western Baltic Sea

“…Differences in prey-specific gastric evacuation rates of crustacean species may lead to the fact that invertebrates with chitinous exoskeletons such as C. maneas remain longer in the stomachs than for example fish prey (Andersen et al, 2016;dos Santos & Jobling, 1995;Temming & Herrmann, 2003). Therefore, the relative composition of stomach contents described here is not the actual prey composition of cod in terms of food intake.…”

Gastric evacuation in European seabass Dicentrarchus labrax (Linnaeus, 1758), forced-fed on commercial pellets

“…The rate of peeling off the mass of the total stomach contents is always the same length as the stomach. If the stomach content is significantly heterogeneous in composition (resistance to digestion or energy density), the mechanistic cylinder model may need to be expanded, according to Andersen et al (2016). Thus, it might be expected that the square root function would also perform better if European seabass is fed voluntarily instead of force-feeding.…”