Survival of Patagonian scallop (Zygochlamys patagonica, King and Broderip, 1832) after the size selection process on commercial fishing vessels

Estimating survival of discarded scallops in the Patagonian scallop fishery: Comment on “Survival of Patagonian scallop (Zygochlamys patagonica, King and Broderip, 1832) after the size selection process on commercial fishing vessels”, by Bremec et al. 2004

“…The experiment was conducted on four different occasions, each occasion retrieving bags after a different total number of days on the seabed, resulting in experimental durations of 5, 6.5, 8 and 12.5 days. Bremec et al (2004) reported high scallop survival (mean = 96%) and no significant differences in scallop survival between control and treatment groups, concluding that the results justify a minimum size limit as a management tool in the Patagonian scallop fishery. Bremec et al (2004) provided size frequency distributions of scallops used in the survival experiment ( Fig.…”

“…Bremec et al (2004) reported high scallop survival (mean = 96%) and no significant differences in scallop survival between control and treatment groups, concluding that the results justify a minimum size limit as a management tool in the Patagonian scallop fishery. Bremec et al (2004) provided size frequency distributions of scallops used in the survival experiment ( Fig. 1) and reported that the mean size of scallops used in the controls was larger than in the treatment.…”

“…1). Moreover, Bremec et al (2004) did not distinguish between undersize (<55 mm) and legal size (>55 mm) scallops in their analysis of survival of discarded scallops. Indeed, the proportion of undersize scallops was significantly higher (80%) in the treatment group than in the control group (36%, p < 0.001, Fig.…”

“…Therefore, analysis of survival of discarded scallops with management implications should focus on undersize scallops, which are actually discarded during fishing operations. Bremec et al (2004) analyzed scallop survival using a two-factor ANOVA with fixed effects (two levels: control and treatment) and random effects (four levels corresponding to each experiment date/duration). Even though the ANOVA showed no significant differences between the survival of treatment and control groups, it showed a significant effect for the experiment date/duration (Bremec et al, 2004, their Table 2) which is not discussed by the authors.…”

Mortality of Animals that Escape Fishing Gears or Are Discarded after Capture: Approaches to Reduce Mortality

“…Lancaster and Frid (2002) estimated that about 80% of undersized brown shrimp survive the capture and discarding processes in the U.K. Solway shrimp fi sheries. The survival of trawl -caught Patagonian scallops was also high even after being subjected to 30 min of on -deck exposure (Bremec et al 2004 ). Sea urchins caught by beam trawl (Kaiser and Spencer 1995 ) and cephalopods caught in pelagic trawls (Hill and Wassenberg 1990 ) exhibited high discard mortality.…”