Abstract
Abstract Effective fishery management measures to protect fish spawning aggregations require reliable information on the spatio-temporal distribution of spawning. Spawning closures have been part of a suite of fishery management actions to rebuild the Gulf of Maine stock of Atlantic cod (Gadus morhua), but difficulties remain with managing rebuilding. The objective of this study was to identify the spatial and temporal distribution of cod spawning during winter in Massachusetts Bay to improve our understanding of cod spawning dynamics and inform fisheries management. Spawning was investigated in collaboration with commercial fishermen during three winter spawning seasons (October 2013–March 2016) using acoustic telemetry and passive acoustic monitoring equipment deployed in fixed-station arrays and mounted on mobile autonomous gliders. Tagged cod exhibited spawning site fidelity and spawning primarily occurred from early November through January with a mid-December peak and some inter-annual variability. The spatial distribution of spawning was generally consistent among years with multiple hotspots in areas >50 m depth. Current closures encompass most of spawning, but important areas are recommended for potential modifications. Utilizing multiple complementary technologies and deployment strategies in collaboration with commercial fishermen enabled a comprehensive description of spawning and provides a valuable model for future studies.
Highlights
The spatial and temporal distribution of the spawning of marine fishes plays a major role in their life history, recruitment success (Cushing, 1990), and interactions with fishing (van Overzee and Rijnsdorp, 2015; Erisman et al, 2017)
The distribution of cod spawning was investigated by combining acoustic telemetry data from individual cod that were tagged when in spawning condition with recordings of cod grunts produced by males as a part of their courtship rituals (Brawn, 1961; Rowe and Hutchings, 2006; Fudge and Rose, 2009) throughout Massachusetts Bay and on Stellwagen Bank (Figure 1b), including portions of the Stellwagen Bank National Marine Sanctuary (NOAA National Centers for Coastal Ocean Science (NCCOS), 2006). Combining data from both approaches provides a holistic description of the spatial and temporal distribution of cod spawning: acoustic telemetry identifies when and where tagged fish returning to the spawning ground aggregate, whereas the passive acoustic recordings provide indications of actual spawning events based on their mating system
This study identified the spatial and temporal distribution of cod spawning during winter in Massachusetts Bay by utilizing multiple acoustic technologies and the local ecological knowledge of collaborating commercial fishermen
Summary
The spatial and temporal distribution of the spawning of marine fishes plays a major role in their life history, recruitment success (Cushing, 1990), and interactions with fishing (van Overzee and Rijnsdorp, 2015; Erisman et al, 2017). Morgan et al, 1997; Dean et al, 2012) and reduce the chances for successful reproduction (Brawn, 1969) These factors make Atlantic cod spawning components vulnerable to extirpation and prime candidates for the application of spawning closures as part of a multifaceted approach to fishery management (Gruss et al, 2014; Zemeckis et al, 2014a; Sadovy de Mitcheson, 2016). Fishery managers have implemented closures to protect spawning aggregations for many cod stocks (e.g. Baltic Sea, International Council for the Exploration of the Sea (ICES), 2004; Iceland, Jaworski et al, 2006), including in the Gulf of Maine (Armstrong et al, 2013) where efforts to eliminate overfishing and achieve rebuilding have not been effective (Rothschild et al, 2014; Northeast Fisheries Science Center, 2017). Declines in abundance of the Gulf of Maine cod stock have been associated with the extirpation of historical spawning components (Ames, 2004; Zemeckis et al, 2014b) and reductions in stock productivity and stability (Reich and DeAlteris, 2009; Kerr et al, 2014)
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