Dead or alive—estimating post-release mortality of Atlantic cod in the recreational fishery

Abstract

Weltersbach, M. S., and Strehlow, H. V. 2013. Dead or alive—estimating post-release mortality of Atlantic cod in the recreational fishery. – ICES Journal of Marine Science, 70: 864–872. Atlantic cod (Gadus morhua) is one of the most important commercial and recreational target species in European marine waters. Recent recreational fisheries surveys revealed that recreational cod catches and release rates are substantial compared to the commercial fishery, particularly in the western Baltic Sea. Despite high release rates, no literature exists exploring the post-release mortality of cod and potential sublethal effects after catch-and-release in recreational fisheries. This study investigates (i) the post-release mortality of undersized cod, (ii) potential factors affecting mortality, and (iii) consequences of the catch-and-release process on cod. During four experimental trials, western Baltic Sea cod were angled from a charter vessel and thereafter observed together with control fish in netpens for 10 d at holding temperatures between 6.2 and 19.8°C. Adjusted mortality rates for angled cod ranged from 0.0–27.3% (overall mean 11.2%). A logistic regression analysis revealed that bleeding and holding-water temperature were the only significant predictors of mortality. Slow hook injury healing (>10 d) and bacterial wound infections were observed in some surviving cod. The results will help to increase the accuracy of recreational cod removal estimates and thereby improve the management of western Baltic cod stock.

Unexpectedly high catch-and-release rates in European marine recreational fisheries: implications for science and management

“…Although a limited number of post-release mortality studies exist on southern European marine species and Atlantic cod (e.g. Aló s, 2008; Aló s et al, 2009b; Veiga et al, 2011;Weltersbach and Strehlow, 2013), the survival rates for most of the presented species in this paper are unknown. Post-release mortality can contribute substantially to the total recreational fishing mortality (Kerns et al, 2012) and can bias current estimates that are based only on harvest data.…”

“…The overall mean release mortality of cod released by anglers from charter boats in the Baltic Sea was estimated to be 11.2% (Weltersbach and Strehlow, 2013). Compared with other species, this percentage is in the lower range (Bartholomew and Bohnsack, 2005) and may, therefore, not be in conflict with the new CFP.…”

“…Length distributions for harvested and released fish were obtained through on-board sampling of charter vessels and data from community fishing events. An experimental containment study conducted in 2012 provided a first mortality rate estimate and an overview of factors that affect the post-release mortality of cod in the Baltic Sea recreational fishery (Weltersbach and Strehlow, 2013). The study was conducted from April 2012 to July 2012 and estimated the immediate and delayed (10 d) mortality of cod caught by recreational anglers from a charter boat.…”

“…¼ 22.0) after adjustment for handling and caging effects. Bleeding and holding-water temperature were found to be significant factors affecting mortality (Weltersbach and Strehlow, 2013). There were no studies available for other fishing modes in the Baltic Sea (i.e.…”

“…However, while catch-and-release (C&R) practices have been thoroughly studied in marine and freshwater recreational fisheries in the USA, Canada and Australia, and for a few freshwater fisheries in Europe Hühn and Arlinghaus, 2011), only very few peer-reviewed publications exist on C&R practices in European marine recreational fisheries (e.g. Aló s, 2008;Aló s et al, 2009aAló s et al, , 2009bVeiga et al, 2011;Ferter et al, 2013;Weltersbach and Strehlow, 2013). In addition to hook and line (angling) with rod and reel or handlines, marine recreational fishers in Europe are locally also allowed to use other gears such as crab pots, gillnets, fykenets, spearguns, and longlines (Pawson et al, 2008;FAO, 2012).…”