Survival of Atlantic cod (Gadus morhua) in the northwest Atlantic longlinefishery

Longline fishing has often been promoted as a clean, low impact fishing met hod. Some longline fishermen and biologists have expressed concern that the re is a high mortality rate for cod and haddock that pass through a dehooki ng device prior to release. The device, aptly called the "crucifier, " usua lly consists of two steel cylinders placed vertically on the gunwale of the vessel. During hauling, the gear passes through the opening between the cy linders while the fish, too large to pass through the narrow opening, is ex cluded. This process pulls the hook from the mouth of the fish and can infl ict severe injuries such as torn and broken jaws. A study was conducted to determine the survival rate of sub-legal cod caugh t in the longline fishery using 11/0 circle hooks. The focus of the researc h was to assess the rate of mortality of sub-legal catch after the cod were placed in cages for 72 hours. The results of the study showed that there w as high mortality (69%) associated with capture using the 11/0 circle hook when the fish were injured by the process of having the hooks removed from their mouths by the crucifier. Furthermore, sublegal cod that had wounds fr om the dehooking process and were under 39 cm were statistically more likel y to die as compared to cod between. 38 and 49 mn. An ancillary set of observations on the predation by sea birds of released sublegal cod was included. Despite low numbers, the findings from these obs ervations show that sea bird predation should be included when estimating t he survival of fish caught by a longline.