Abstract
Northern shortfin squid (Illex illecebrosus) have presented a challenge for US fishery management because of their life history traits and broad population distribution. They are characterized by a short semelparous lifespan and high interannual variability in recruitment. Much of the stock resides outside of the boundaries of existing US fisheries surveys and US fishing effort. Based on the annual migration pattern and broad geographic distribution of shortfin squid, it is believed that the US squid fishery in the Mid-Atlantic has not had a substantial impact on the stock; however, recent catches are viewed as tightly constrained by quotas. To better estimate the potential impact of fishing on the resource, we worked with industry representatives, scientists, and managers to estimate the availability of the northern shortfin squid stock on the US continental shelf to the US fishery. Taking a novel analytical approach, we combine a model-based estimate of the area occupied by northern shortfin squid with the empirical US commercial shortfin squid fishery footprint to produce estimates of the area of overlap. Because our method overestimates the fishery footprint and underestimates the full distribution of the stock, we suggest that our estimates of the overlap between the area occupied by the squid and the fishery footprint is a way to develop a conservative estimate of the potential fishery impact on the stock. Our findings suggest a limited degree of overlap between the US fishery and the modeled area occupied by the squid on the US continental shelf, with a range of 1.4–36.3%. The work demonstrates the value of using high-resolution, spatially explicit catch and effort data in a species distribution model to inform management of short-lived and broadly distributed species, such as the northern shortfin squid.
Highlights
There are many uncertainties inherent in fisheries science and management
We propose to use the proportion of the occupied area on the US continental shelf as estimated by a species distribution model overlapped by the US fishery footprint to calculate a conservative estimate of stock availability to the fishery as an approximation of the potential impact of the fishery
Some proportion of the shortfin squid stock migrates inshore from the shelf edge to occupy summer and fall feeding and spawning habitats (Hendrickson, 2004) on the US and Canadian continental shelf and in waters managed by the Northwest Atlantic Fisheries Organization (NAFO), while the remaining proportion of adults and juveniles remain in the shelf slope sea (e.g., Rathjen, 1981; Roper et al, 2010; Shea et al, 2017)
Summary
There are many uncertainties inherent in fisheries science and management. For example, natural mortality, catchability, and recruitment dynamics are often unknown. Some proportion of the shortfin squid stock migrates inshore from the shelf edge to occupy summer and fall feeding and spawning habitats (Hendrickson, 2004) on the US and Canadian continental shelf and in waters managed by the Northwest Atlantic Fisheries Organization (NAFO), while the remaining proportion of adults and juveniles remain in the shelf slope sea (e.g., Rathjen, 1981; Roper et al, 2010; Shea et al, 2017). We adopted a conservative approach to develop estimates of the availability of shortfin squid to the fishery (ρ) and proportional escapement (1 - ρ) by confining analysis to fishery-dependent and fishery-independent survey data collected in US continental shelf waters. We discuss the value of our approach and findings to precautionary fisheries management
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