A century of fish growth in relation to climate change, population dynamics and exploitation

Abstract

Marine ecosystems, particularly in high‐latitude regions such as the Arctic, have been significantly affected by human activities and contributions to climate change. Evaluating how fish populations responded to past changes in their environment is helpful for evaluating their future patterns, but is often hindered by the lack of long‐term biological data available. Using otolith increments of Northeast Arctic cod (Gadus morhua) as a proxy for individual growth, we developed a century‐scale biochronology (1924–2014) based on the measurements of 3,894 fish, which revealed significant variations in cod growth over the last 91 years. We combined mixed‐effect modeling and path analysis to relate these growth variations to selected climate, population and fishing‐related factors. Cod growth was negatively related to cod population size and positively related to capelin population size, one of the most important prey items. This suggests that density‐dependent effects are the main source of growth variability due to competition for resources and cannibalism. Growth was also positively correlated with warming sea temperatures but negatively correlated with the Atlantic Multidecadal Oscillation, suggesting contrasting effects of climate warming at different spatial scales. Fishing pressure had a significant but weak negative direct impact on growth. Additionally, path analysis revealed that the selected growth factors were interrelated. Capelin biomass was positively related to sea temperature and negatively influenced by herring biomass, while cod biomass was mainly driven by fishing mortality. Together, these results give a better understanding of how multiple interacting factors have shaped cod growth throughout a century, both directly and indirectly.

Multidecadal changes in fish growth rates estimated from tagging data: A case study from the Eastern Baltic cod (Gadus morhua, Gadidae)

“…Denechaud et al. (2020), using otolith increments data, revealed significant variations in Northeast Arctic cod growth over the last century, but no declining trend has been detected in the recent period. Long time series of weight‐at‐age data are available and routinely used for stock assessment also for the other North Atlantic cod stocks.…”

Genomic prediction of growth in a commercially, recreationally, and culturally important marine resource, the Australian snapper (Chrysophrys auratus)

“…These characteristics make growth and related traits major targets for selective breeding and human-induced evolution studies (Sharpe and Hendry 2009; Gjedrem et al . 2012; Denechaud et al . 2020; Huang et al .…”

“…Fish growth rates can respond rapidly to external selective pressures by phenotypic plasticity or by changes in genotypic frequencies in the population (Bowles et al . 2020; Denechaud et al . 2020; Oke et al .…”

“…2021). Fish growth is also a quantitative trait that is easy to measure, and as such, can be used to assess physiological and demographic responses to human-mediated environmental changes (Denechaud et al . 2020).…”

“…2016; Dijoux and Boukal 2021). However, size-selective harvesting and climatic effects could be species and system specific (Denechaud et al . 2020), and despite increasing concerns, the evolutionary consequences have so far been investigated in only a limited number of species.…”