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Cod Conservation

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By William Hoffman
Project Leader for Fisheries Dependent Investigations and Special Projects

MarineFisheries has embarked on a new conservation strategy for Atlantic cod (Gadus morhua): surgical temporal and spatial closures now protect remnant Gulf of Maine cod spawning aggregations. Research conducted on these protected aggregations shows this approach has tremendous promise.

Atlantic cod is a mainstay of the Gulf of Maine (GOM) groundfish fishery. It is highly sought after and has supported large-scale commercial and recreational fisheries for generations. Due to high demand, over-harvesting led to past collapses of cod stocks throughout the species’ range in Europe, Canada, and the US.

Protecting spawning aggregations is a critical component of meeting the challenges to rebuild and restore the historic size and distribution of GOM cod and ensure its long-term commercial and biological sustainability. Through scientific studies and interviews with commercial fishermen, it has been reported there are two components of the GOM stock: one found near-shore (between 20-30 nautical miles off the coast) and another on offshore banks and sills of deep basins (both components typically aggregate inshore to spawn). However, the GOM cod stock complex is a mosaic of distinct or semi-distinct spawning groups (subpopulations), many of which are migratory.

Through tagging and acoustic telemetry studies, it has been shown that mature cod show a high level of spawning site fidelity, and some aggregations over-winter in close proximity to their spawning grounds.


Newly published work has demonstrated that spawning groups are genetically unique, indicating they function independently of one another. Conservation and rebuilding of inshore stocks will help protect genetic diversity and increase resiliency enabling cod to better adapt to change and disruptions. The more subpopulations that exist in the GOM system, the more likely larvae will find suitable settlement habitat, resulting in improved recruitment.

Research also suggests protecting the remaining inshore stocks could act as a source for recolonizing unoccupied spawning grounds in Massachusetts, New Hampshire and Maine, resulting in the resurrection of historic spawning areas. The restoration of inshore stocks would strengthen smallboat commercial fisheries and private/charter recreational fisheries thereby increasing their financial contributions to local economies.

For the past several decades, cod have been managed according to large geographical units (e.g. Gulf of Maine, Georges Banks, etc), as managers have preferred to set targets for large areas rather than micro-manage individual sub-populations. Although some success has been achieved with this method, restoring the historical redistribution, and thereby ensuring long-term sustainability, has proven difficult. A major challenge has been the demise of many of the spawning aggregations that once existed on Nantucket shoals, Massachusetts Bay, Ipswich Bay and downeast Maine.

Cod Closure Underwater.psd

MarineFisheries has created winter and spring Cod Conservation Zones (CCZ) in state waters. By protecting Massachusetts Bay and Ipswich Bay spawners, which have already been found to be genetically isolated, researchers and managers are working together to understand the fine-scale population structure of cod and prevent depletion of these subpopulations through localized overexploitation.

Working through the Massachusetts Marine Fisheries Institute (MFI), a partnership between MarineFisheries and the University of Massachusetts/School for Science and Marine Technology (SMAST), studies using acoustic telemetry, data storage tags, traditional tags, and underwater video have improved understanding of the fine-scale population structure of inshore cod, as well as their behavior and movement patterns. Results of these efforts support protection of spawning aggregations that represent the few known remnants of once numerous and diverse historical spawning groups in the Gulf of Maine.

Current research projects are occurring not a moment too soon. The New England Fishery Management Council’s new system of groundfish management (sector management) has direct consequences for inshore GOM cod. Rather than using time-area closures (rolling closures) and trip limits to control fishing effort, sector management apportions total allowable catch into catch shares. As a result, areas that were once closed to control fishing effort under the old management scheme are now open for harvest. Unfortunately, some of these areas include critical cod spawning grounds.

One such area known as “Whaleback” is located in northern Ipswich Bay, adjacent to New Hampshire state waters. Not only is this unique aggregation now vulnerable to commercial fishing, the recreational fishing fleet has also become aware of its existence and is currently exerting significant pressure. If left unprotected, it is likely that Whaleback will be unable to withstand this level of exploitation, and the aggregation may disappear like so many others along the inshore GOM.

Current management of the GOM cod complex has been effective to a point; however, until the protection of inshore spawning aggregations is secured, complete rebuilding may not be possible. Through continued research efforts such as the ongoing MarineFisheries CCZ projects, we will be able to enhance our understanding of GOM cod behavior and population structure. We are hopeful that this information will prove instrumental in formulating creative management solutions that will allow GOM cod to continue to rebuild, ultimately resulting in a more sustainable fishery for the future. The CCZ closures are set to expire in February 2011, MarineFisheries will be looking to renew this conservation measure in the coming months.

Regulations in red are new this year.

Purple text indicates an important note.

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