Oceanographic habitat suitability is positively correlated with the body condition of a coastal‐pelagic fish

Abstract

Species distribution models are commonly used to determine a species’ probability of occurrence but have not been used to examine the effect of environmental habitat suitability on fish condition, which is considered to be an integrated measure of physiological status. Here, we test for a relationship between oceanographic habitat suitability and the body condition of kingfish (Seriola lalandi) from eastern Australia. We (a) test whether individuals sampled from areas of high‐quality habitat were in better condition than individuals sampled from areas of low‐quality habitat, and (b) assess whether the condition of kingfish responded to oceanographic habitat suitability predicted at varying time‐before‐capture periods. Kingfish habitat was modelled as a function of sea surface temperature, sea‐level anomaly and eddy kinetic energy in a generalized additive modelling framework. Model predictions were made over one‐ to six‐week time‐before‐capture periods and compared to field‐derived kingfish condition data measured using bioelectrical impedance analysis. Oceanographic habitat suitability was significantly correlated with kingfish condition at time‐before‐capture periods ranging from one to four weeks and became increasingly correlated at shorter lead‐times. Our results highlight that (a) fish condition can respond sensitively to environmental variability and this response can be detected using oceanographic habitat suitability models, and (b) climate change may drive extensions in species range limits through spatial shifts in oceanographic habitat quality that allow individuals to persist beyond historical range boundaries without their body condition being compromised.

Maximising the utility of bioelectrical impedance analysis for measuring fish condition requires identifying and controlling for sources of error

“…To assess for potential source of error that may influence phase angle values measured during opportunistic field-based sampling, kingfish were sampled from south-eastern Australia using hook-and-line fishing between November 2016 and February 2019 for experimental analyses. Kingfish were chosen so that the experimental results herein could be used to inform a broader ecological study that aimed to measure the body condition of this species across a gradient of oceanographic habitat suitability (Champion et al, 2020). Kingfish from south-eastern Australia represent a single, genetically distinct population (Miller et al, 2011) with a distribution that is influenced by oceanographic variables, including sea surface temperature, sea level anomaly and current velocity (Brodie et al, 2015;Champion et al, 2018).…”

“…Measurements taken within approximately 10 hours of fish death, provided fish are held on ice, should yield robust data. Heintz, 2009 Cox et al, 2011 Experiment 1 herein Comparable condition measures were taken on kingfish (Seriola lalandi) between 0 and 15 hours since death while fish were held on ice (Champion et al, 2020).…”

“…To yield comparable data, temperature effects have been controlled for by icing fish for 1 hour before taking condition measurements (Champion et al, 2020).…”

“…Experiment 3 herein In a comparison of the body condition of kingfish (Seriola lalandi) from eastern Australia, only whole fish were selected for sampling (Champion et al, 2020).…”

“…Measures of fish condition can reveal important biological and ecological relationships, such as variation in growth and recruitment of spatially discrete stocks (Rätz and Lloret, 2003) and the influence of abiotic factors on the physiology of fishes (Adams et al, 2018;Kjesbu et al, 2014). Given that environmental variables are known to influence fish condition (Willis and Hobday, 2008;Champion et al, 2020), and that climate-driven oceanographic changes are rapidly occurring globally (Wu et al, 2012), body condition indices are a useful approach to assess species' responses to environmental change (Miranda et al, 2019).…”