Using otolith chronologies to understand long‐term trends and extrinsic drivers of growth in fisheries

Abstract

Identifying trends and drivers of fish growth in commercial species is important for ongoing sustainable management, but there is a critical shortage of long-term datasets in marine systems. Using otolith (ear bone) sclerochronology and mixed-effects modeling, we reconstructed nearly four decades (37 yr) of growth across four oceanographically diverse regions in an iconic fishery species, snapper (Chrysophrys auratus). Growth was then related to environmental factors (sea surface temperature, chlorophyll-a, and Southern Oscillation Index) and population performance indicators (recruitment and commercial catch). Across the decades, growth rates declined in the two most productive fishery regions. Chlorophylla (a measure of primary productivity) was the best predictor of growth for all regions, but direction and magnitude of the relationships varied, indicating regional-specific differences in intra-specific competition. Sea surface temperature was positively correlated with fish growth, but negatively correlated after temperature reached optimum thermal maxima, which suggests individuals in warmer regions may be under thermal stress. Growth also decreased at the extremes of the Southern Oscillation Index, indicating fish growth is impeded in significant climatic events. Contrasting relationships between growth, catch, and recruitment indicated regional-specific density-dependent effects, with growth positively correlated with population size in one region but negatively correlated in another. Our results indicate that under future ocean warming and increased frequency of extreme climate events, fish growth and fisheries productivity are likely to be affected. Furthermore, the interactive effects of extrinsic factors also indicated that stressors on fisheries should be managed collectively. We show that otolith chronologies are an effective method to assess long-term trends and drivers of growth in fishery species. Such informed ecological predictions will help shape the sustainable management of fisheries under future changing climates.

Port Jackson Shark Growth Is Sensitive to Temperature Change

“…variation of growth rates (Conover and Present, 1990). It is anticipated that under forecast climate scenarios, species are likely to be increasingly exposed to periods of suboptimal local environmental conditions, which in turn exacerbates the frequency and magnitude of variability in population growth (Neuheimer et al, 2011;Martino et al, 2019). More broadly, these findings provide indirect support of Bergmann's Rule in poikilotherms (Conover, 1990;Meiri, 2011), and suggest that in the absence of genetic variability within the Gulf St Vincent Port Jackson shark subpopulation (Izzo, unpublished data), population growth is primarily influenced by local environmental factors (Lombari-Carlson et al, 2003).…”

“…However, targeted fishing pressure has been attributed to shifts in shark population growth (Lombari-Carlson et al, 2003) and length-at-age dynamics (Walker et al, 1998), as well as other broader ecological processes (Stevens et al, 2000). Biochronologies provide a means to explore the influence of fishing on population growth (e.g., Martino et al, 2019).…”

Century-long cod otolith biochronology reveals individual growth plasticity in response to temperature

“…In the third step, we used within-group centering 21 to determine if average population growth response to the temperature variability was dominated by a within-individual or an among-individual effect, i.e. individual phenotypic plasticity or among-individual differences in the environmental conditions 9,44 . Using this technique, we replaced a temperature variable in the model by two new variables: (1) the average temperature conditions experienced by individuals across their lifetime and (2) the deviations of temperature from this mean; and compared to the baseline extrinsic model using AICc.…”

Growth impacts in a changing ocean: insights from two coral reef fishes in an extreme environment

“…calendar growth year ('Year') were respectively assigned to each increment (Table 3). The first two annual increments were not used in the analysis due to poor visualization in the inner region of the otolith, while the last (marginal) increments were excluded because they did not represent a full year of growth (Doubleday 2015;Martino et al 2019). For each region, the sample size was at least five increment measurements per calendar year.…”