Identifying the distribution of Atlantic cod spawning using multiple fixed and glider-mounted acoustic technologies

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.

A decade of monitoring Atlantic cod Gadus morhua spawning aggregations in Massachusetts Bay using passive acoustics

“…3S or 7W) and treated as a separate location (Table 1). Although admittedly an arbitrary threshold, 2 km appeared to be a reasonable resolution given the spatial scale and patterns ob served in Zemeckis et al (2019). Most sites that retained their original labels moved far less than 2 km.…”

“…A total of 17 MARUs were deployed, of which 13 provided usable data. The sites were chosen as part of a multidisciplinary study investigating Atlantic cod spawning sites which paired telemetry-based movement of tagged individuals with both bottom-mounted and mobile passive acoustics to target cod spawning aggregations (Zemeckis et al 2019). Site selection was based on various sources, including previous PAM (Morano et al 2012, Hernandez et al 2013, trawl survey data, fishery observer data, and ecological knowledge from collaborating commercial fishermen.…”

“…Long-term PAM is used to study decadal trends in the occurrence and distribution shifts of marine mammals (Van Parijs et al 2009, Davis et al 2017 and is increasingly being used to monitor fish occurrence and behavior (Locascio & Mann 2008, Mann et al 2009, Širović et al 2009, Nelson et al 2011, Aalbers & Sepulveda 2012, Bolgan et al 2018, Zemeckis et al 2019. Calling activity has been linked to reproductive behavior in many other fishes, including pomacentrids (Mann & Lobel 1995), batra choidids (McKibben & Bass 1998), sciaenids (Locascio & Mann 2008), and serranids (Rowell et al 2015).…”

Temporal and spatial distributions of delphinid species in Massachusetts Bay (USA) using passive acoustics from ocean gliders

“…Increased whistle detections closer to Stellwagen Bank, as well as the presence of echolocation clicks and some presumed foraging buzzes on our glider recordings, suggest that the Stellwagen Bank area may be a foraging ground for delphin ids. Acoustic detections of Atlantic cod were concentrated in northern Stell wagen Basin (Zemeckis et al 2019) where few delphinid detections were recorded, suggesting that delphinids were not targeting this species. Several fish species, including silver hake and haddock, move into deeper waters in the Gulf of Maine in winter and are documented prey for Atlantic white-sided dolphins (Craddock et al 2009) and the closely related white-beaked dolphin Lagenorhynchus albi ros tris (Canning et al 2008).…”

“…In 2013, a multi-year effort began to study the winter distribution of spawning Atlantic cod in western Massachusetts Bay using passive acoustics from ocean gliders (Zemeckis et al 2019), which provided an opportunity to concurrently monitor odontocete occurrence using passive acoustics. This work aimed to increase our understanding of delphinid habitat use in Massachusetts Bay during late fall and early winter.…”