Quasi‐Stationary Atlantic Cod Bycatch Estimation in the Maine American Lobster Homarus americanus Trap Fishery

Abstract

The Atlantic Cod Gadus morhua population in the Gulf of Maine (GOM) is currently near historically low levels of abundance. Reliable estimates of incidental Atlantic Cod bycatch from Maine's American lobsterHomarus americanus fishery, which are unavailable and not included in the current stock assessment, are potentially critical for understanding complete catch dynamics and are thus essential for rebuilding the stock. Available fishery-dependent data cannot be used directly in estimating Atlantic Cod bycatch because of nonrandom spatial and temporal sampling efforts. We developed a standardized framework for estimating Atlantic Cod bycatch in Maine's inshore lobster fishery for the years 2006-2013. We employed environmental covariates in a bootstrapped generalized additive model framework to standardize monthly zonal Atlantic Cod bycatch per unit effort (BCPUE) and lobster CPUE. Bootstrapped distributions of standardized CPUE and BCPUE were combined with landings data to estimate spatiotemporally explicit confidence intervals of Atlantic Cod discards in the Maine lobster fishery. Modeling results remained consistent throughout the study years, suggesting robustness in our approach. The estimates of Atlantic Cod discards in the lobster fishery improve the understanding of the total GOM Atlantic Cod bycatch and help to address current stock assessment deficiencies.

Bycatch estimation of narrow‐clawed crayfish (Pontastacus leptodactylus) in Turkish fyke net fisheries

“…Discard rates due to lesions were higher in Eğirdir Lake and Porsuk Dam than other lakes, possibly due to lower virulence of the disease due to environmental effects (e.g., pH, temperature, or conductivity). Some illegal or inadvertently detained bycatch can be sold (Boenish & Chen, 2018), although some portion of the catch may be thrown back into the water dead or in poor condition. Bycatch can sometimes turn into an economic gain for fishermen, but most is discarded (e.g., dumped overboard; Raby et al, 2011).…”

“…Bycatch is one of the most pervasive problems in modern‐day fisheries (Boenish & Chen, 2018), commonly identified as ‘catch of organisms that are not targeted’ (Pérez Roda et al, 2019). Bycatch and discards cause unnecessary mortalities in fisheries that threaten fisheries sustainability by causing overfishing (FAO, 2018; Pérez Roda et al, 2019).…”

Estimating the Discard Mortality of Atlantic Cod in the Southern Gulf of Maine Commercial Lobster Fishery

“…Moreover, Atlantic Cod CPUE in commercial lobster gear is relatively low. Models that were produced using observer data indicated that the probability of capturing Atlantic Cod as bycatch in a commercial lobster trap was less than 0.1% in LMZ G from 2006 to 2013, with approximately 40,000–50,000 Atlantic Cod discarded per year (Boenish and Chen 2017). To estimate the weight of Atlantic Cod discards from 2006 to 2013, it was assumed that individuals observed in this study reflected the length distribution of Atlantic Cod bycatch within the commercial lobster fishery.…”

“…Although this estimate was provided as evidence to support a ban on lobster gear in known Atlantic Cod spawning grounds (Bell 2014a), industry stakeholders and the Maine Department of Marine Resources fought this measure due to the absence of a dedicated study of Atlantic Cod bycatch in the fishery and concerns about the validity of the data in the Marine Stewardship Council’s report (MEDMR 2012; Keliher 2014; Bell 2014b). While this bycatch estimate has raised concerns for the Atlantic Cod stock (Keliher 2014; Bell 2014), understanding whether these fish survive after capture and handling is necessary to document the true impact of the GOM commercial lobster fishery on Atlantic Cod (MEDMR 2012; Boenish and Chen 2017, 2020).…”