Spawning site fidelity by Atlantic cod (Gadus morhua) in the Gulf of Maine: implications for population structure and rebuilding

Abstract

Rebuilding the Gulf of Maine stock of Atlantic cod (Gadus morhua) has been much slower than expected. An important source of scientific uncertainty contributing to the difficulties in managing rebuilding has been the lack of understanding of cod population structure. Previous research indicates that the stock functions as a metapopulation that is made up of multiple subpopulations and many finer-scale spawning components. This study investigated fine-scale, multiyear spawning site fidelity by a spring-spawning component of Atlantic cod in the western Gulf of Maine. Movements of acoustically tagged cod (n = 63) with respect to a known spawning site were tracked using passive acoustic telemetry. A large proportion (38–67%) of tagged cod exhibited spawning site fidelity between 2010 and 2012. After adjusting for fishing mortality, natural mortality, and skipped spawning, the estimated rate of spawning site fidelity ranged between 47 and 95% in 2011. Multiyear spawning site fidelity was also observed, with individuals being tracked for up to four consecutive spawning seasons. Spawning site fidelity serves as one of the multiple mechanisms that contribute to the formation and maintenance of the observed metapopulation structure. Spawning site fidelity also reduces the reproductive connectivity among spawning sites, thus delaying both recolonization of abandoned spawning sites and stock rebuilding. Future stock assessment models and fishery management plans that incorporate the metapopulation structure of cod in the Gulf of Maine are expected to be more effective at preventing continued declines in spawning diversity and promoting rebuilding.

Assessing reproductive behavior important to fisheries management: a case study with red drum, Sciaenops ocellatus

“…These site fidelity rates are similar to those observed in Atlantic cod in the Gulf of Maine, where it has been recognized that inclusion of the metapopulation structure in stock assessments and fishery management plans would help prevent continued declines in spawning diversity and help promote the rebuilding of the stock (Zemeckis et al. ). However, in this study, a relatively large number of acoustically tagged adults were never detected ( n = 23), potentially due to delayed mortality after the implantation process.…”

“…Spawning site fidelity is a mechanism that contributes to the formation and maintenance of metapopulation structure, reducing reproductive connectivity between spawning sites and delaying recolonization of fished out spawning sites (Zemeckis et al. ). Spawning site fidelity is commonly assumed to occur at the lifetime scale.…”

“…, Zemeckis et al. ) and how movement patterns associated with this behavior can affect fisheries selectivity (Nielsen and Berg , Villegas‐Ríos et al. ), productivity (Goethel et al.…”

Acoustic telemetry and fisheries management

“…, Zemeckis et al. ). Similarly, the common snook ( Centropomus undecimalis ) has also been shown to exhibit strong spawning site fidelity (Lowerre‐Barbieri et al.…”

“…To put the power of such integrated network collaborations into context, see the work of Jorgensen et al. (), which pooled the acoustic data from several independent research groups to describe the Pacific migrations of white sharks ( Carcharadon carcharius ).…”