Using model selection to choose a size‐based condition index that is consistent with operational welfare indicators

Abstract

Quantitative and qualitative measures of fish health and welfare are essential for management of both wild capture and aquaculture species. These measures include morphometric body condition indices, energetic condition and aquaculture operational welfare indicators (OWIs). Measures vary in ease of measurement (and may require destructive sampling), and it is critical to know how well they correlate with fish health and welfare so appropriate management decisions can be based on them. Lumpfish (Cyclopterus lumpus) is a new farming species that needs nondestructive OWIs to be developed and validated. In this study, we developed a C. lumpus fin damage score. Four different body condition indexes based on individual weight relative to either length–weight relationships or relative to other fish in its local environment were tested (using model selection) as predictors of individual fin damage. Results showed severity of fin damage was predicted by small size relative to the other individuals in the tank or cage. Body condition based on length–weight relationship was not found to predict fin damage, indicating that using established indices from fisheries or from other species would not predict welfare risks from fin damage. Implications are that especially in hatchery conditions grading will improve the condition index, and is expected to mitigate fin damage, but that low weight at length was not of use in predicting fin damage. Model selection to choose between a suite of possible indices proved powerful and should be considered in other applications where an easily measured index is needed to correlate with other health measures.

Welfare Indicators in Tilapia: An Epidemiological Approach

“…The decrease in fish weight is one of the main concerns among aquaculturists; it is very difficult to observe growth with the naked eye but, feasible to follow the development of the pond over time, during cultivation, in the unfolds and pond changes. According to Rey et al ( 57 ), the weight and the comparison of this value must be done by pond because each cage or pond behaves differently. They have their environment.…”

The behavior and welfare of neglected species: some examples from fish and mammals

“…Atlantic lumpfish ( Cyclopterus lumpus ) are a teleost (bony) marine fish that are used as biological control agents in Atlantic salmon ( Salmo salar ) farming where their role is to act as “cleaner fish” to eat sea lice from the bodies of sea caged salmon ( Boissonnot et al, 2023 ). Cleaner fish also include other species such as fishes from the Labridae family (ballan ( Labrus bergylta ), corkwing ( Symphodus melops ) and goldsinny wrasse ( Ctenolabrus rupestris ) ( Powell et al, 2018 ; Rey et al, 2021 ), and these were first used in salmon aquaculture in the 1980s ( Bjordal, 1988 ; Deady, Varian & Fives, 1995 ). However, currently only two species are farmed for this purpose, and these are ballan wrasse and lumpfish ( Brooker, Skern-Mauritzen & Bron, 2018 ).…”

“…After 1 year the adults move to the open ocean where they feed on plankton before returning 2–4 years later to coastal areas to spawn ( Imsland & Reynolds, 2022 ). They are a non-shoaling species so do not form groups but there is evidence of aggression and the formation of dominance hierarchies ( Rey et al, 2021 ). Lumpfish feed on large planktonic organisms at the surface or mid-water and their diet includes zooplankton, fish eggs, and small crustaceans ( Davenport, 1985 ; Kennedy et al, 2016 ).…”

“…These tanks were 1.3 m 3 round PVC black tanks (150 cm diameter × 80 cm depth) at stocking densities of 10–15% (~12 kg/m 3 ). The temperature ranged from 8.2 °C (January) to 14.2 °C (October) suggesting a flow through system since temperature was not constant ( Rey et al, 2021 ). No enrichment is described but it is possible these lumpfish could adhere to the bottom or sides of the tanks to meet their behavioral needs since wild individuals at this development stage are found adhering to rocks or algae.…”

“…Growth rates, body condition and survival (or mortality) rates have been used by several studies at different developmental stages of lumpfish including larval, on growing and adult lumpfish ( Powell et al, 2018 ; Dahle et al, 2020 ; Geitung et al, 2020 ; Rey et al, 2021 ). Of course, the premise used here is that if the animals are growing, are in better condition and are surviving between different experimental groups one can identify the optimal welfare conditions to house or farm lumpfish in.…”