Temporal variability in size and growth of Atlantic herring in the Gulf of Maine

Abstract

Variability in life history traits and structural diversity of commercially exploited fishes in response to stress can impact their population dynamics and sustainability. Using data from a fishery dependent sampling program from 1978 to 2011, we evaluated temporal variability of size and growth of adult Atlantic herring (Clupea harengus) in the Gulf of Maine. We then developed and tested the hypotheses on the links of such temporal changes to population density and environmental factors and found decreases in size and growth potential. Generalized additive models found that density dependence was the main driver of such changes over sea surface temperature and salinity. Our results highlight the importance of density dependent processes in regulating growth and population size structure for Atlantic herring in the Gulf of Maine. 1 | INTRODUCTION The structural diversity of life history traits (e.g., size and age) within and among fish populations is an important consideration that may impact the population dynamics and productivity of managed fish stocks (Hilborn & Walters, 1992; Ricker, 1975). Large variations in size and age diversity have been demonstrated among populations, as well as within populations among years, and can be related to various biotic and abiotic factors (e.g., population density, prey availability, temperature and salinity) (Blaxter, 1992; Chen & Mello, 1999; Hare et al., 2016; Yan et al., 2012). Additionally, truncated size and age distributions can indicate a stressed stock due to overfishing (Brunel & Piet, 2012). As such, an understanding of the complex relationship between fish populations and their environment is important for investigating the potential impact of environmental changes on fish population dynamics (Fischer et al., 2013). An inverse relationship between spawning stock biomass (SSB) and growth, as well as a decline in asymptotic length per unit biomass density, has been described (Lorenzen & Enberg, 2002; Walters & Post, 1993). The parameters of the Von Bertalanffy growth function (VBGF) maximum attainable length (L ∞), maximum attainable weight (W ∞) and the Brody growth rate (K) are influenced by density-dependent growth.

Coherent long‐term body‐size responses across all Northwest Atlantic herring populations to warming and environmental change despite contrasting harvest and ecological factors

“…However, the finding that only three of the seven time‐series examined were negatively correlated with lifetime average biomass contradicts this expectation. The lack of consistency in density‐dependence among populations, despite large changes in herring biomass in a number of locations, suggests that the importance of this process may well have been overestimated in previous analyses on some of these populations (Becker et al., 2020; Brunel & Dickey‐Collas, 2010). It also implies that reductions in population density associated with overfishing and/or low recruitment are unlikely to have resulted in shared compensatory increases in juvenile growth rate across the NWA (Croll et al., 2023; Rose et al., 2001; Trochta et al., 2020).…”

“…The dataset for Canadian herring populations was complemented with published estimates of mean length‐at‐age 4 for herring from the Gulf of Maine obtained from Figure 4a of Becker et al. (2020). These data had originally been collected by purse seines in the months of June and July and subsequently adjusted to the same date of capture, and include herring aged 4 years in cohorts from 1974 to 2007.…”