Modelling gastric evacuation in gadoids feeding on crustaceans

Area of Science:

• Ecology
• Fisheries Science
• Animal Physiology

Background:

• Gastric evacuation models are crucial for understanding fish feeding ecology and estimating food consumption rates.
• Previous models often simplify prey digestion, particularly for armored prey like crustaceans.
• Predatory fish consume various crustacean species, necessitating models that account for prey structural differences.

Purpose of the Study:

• To expand a mechanistic, prey surface-dependent model for gastric evacuation in predatory fish.
• To incorporate the effect of robust crustacean exoskeletons into digestion and evacuation rate predictions.
• To provide a tool for estimating fish food consumption from stomach content data.

Main Methods:

• Modified a mechanistic model by adding a resistance layer to simulate crustacean exoskeleton digestion.
• Split prey evacuation into two stages: exoskeleton cracking and digestion/evacuation of remains.
• Parameterized the model using data from Atlantic cod (Gadus morhua) and whiting (Merlangius merlangus) fed various crustaceans (krill, shrimp, crabs).

Main Results:

• The model successfully described gastric evacuation independent of meal and prey size, based on exoskeleton mass.
• Increased chitin and ash content (armor level) in crustaceans prolonged the first evacuation stage (0-33 h) and halved the rate of both stages.
• Potential for interspecific model parameterization within prey categories (krill, shrimp, crab) if armor content is similar.

Conclusions:

• Crustacean exoskeleton properties significantly influence gastric evacuation rates in predatory fish.
• The enhanced model provides a more accurate method for estimating evacuation rates and fish food consumption.
• This approach is valuable for fisheries management and ecological studies, particularly when digestion stage data is available.