Effects of marine reserve protection on the mud crab Scylla serrata in a sex-biased fishery in subtropical Australia

Abstract

The impact of sex-biased fishing and marine reserve protection on the mud crab Scylla serrata was examined by comparing the catch rates (catch-per-unit-effort, CPUE), mean size, sex ratios and movement of crabs in 2 coastal marine reserves (1.9 and 5.7 km 2 ) and 4 fished non-reserve sites in subtropical Australia. Five years after closure, both marine reserves supported higher catch rates and a larger mean size of S. serrata than non-reserve sites. Males dominated catches of S. serrata in both marine reserves, where CPUE was at least twice as high within the reserves compared to non-reserve sites. Male crabs were also 10% larger in the reserves compared to adjacent fished areas, and of the total male catch, over 70% were equal to or greater than legal size compared to less than 50% outside the reserves. The sex ratio of S. serrata was skewed towards females in all nonreserve sites, which was most likely a result of the ban on taking female S. serrata in Moreton Bay. As only male crabs of ≥15 cm CW made up the S. serrata fishery in Moreton Bay, sex ratios of mature male and female crabs were examined, revealing a strong skew (2:1) towards mature males in both marine reserves. Of the 472 S. serrata captured in this study, 338 were tagged in the reserves in order to document movement of the crabs between the reserve and non-reserve sites. Of the 37 recaptured crabs, 73% were recorded inside the reserves, with some spillover (i.e. cross-boundary movement) of crabs recorded in fished areas. This study demonstrates the effectiveness of small (< 6 km

Life-history, movement, and habitat use of Scylla serrata (Decapoda, Portunidae): current knowledge and future challenges

“…In Queensland, Australia, the fishing regulations only allow large (C150 mm CW) males to be taken, which results in increasing numbers of large females compared to males. This shift can be reversed with the implementation of marine protected areas (MPAs) where fishing is prohibited (Pillans et al, 2005;Butcher et al, 2014;Alberts-Hubatsch, pers. observation).…”

Impacts of Large Male-Selective Harvesting on Reproduction: Illustration with Large Decapod Crustacean Resources

“…the large male-selective harvesting) (e.g. Ennis et al 1990;Smith and Jamieson 1991;Rugolo et al 1998;Pillans et al 2005). Such harvesting affects the demography of the population by skewing the sex ratio towards females and decreasing mean male body size (Smith and Jamieson 1991;Abbe and Stagg 1996;Rowe and Hutchings 2003;Pillans et al 2005;Fenberg and Roy 2008).…”

“…Ennis et al 1990;Smith and Jamieson 1991;Rugolo et al 1998;Pillans et al 2005). Such harvesting affects the demography of the population by skewing the sex ratio towards females and decreasing mean male body size (Smith and Jamieson 1991;Abbe and Stagg 1996;Rowe and Hutchings 2003;Pillans et al 2005;Fenberg and Roy 2008). In such harvested populations, small males replace large males in reproduction and remaining males participate in more matings than in pristine populations (Ennis et al 1990;Sainte-Marie 1993;Carver et al 2005;Milner et al 2007).…”

The Relative Importance of the Sedge Island Marine Conservation Zone for Adult Blue Crabs in Barnegat Bay, New Jersey

“…The abundance of males is higher in the SIMCZ compared with other SAV-dominated locations, although not Blue Crabs within Marine Conservation Zonesignificantly, compared with the neighboring location, suggesting the SIMCZ does not significantly enhance the abundance of males in adjacent areas via a ''spill-over'' effect, as seen in other species protected by MPAs (Pillans et al, 2005;Russ, Alcala, and Maypa, 2003;Stobart et al, 2009). Additionally, the SIMCZ has a distinct size frequency distribution of males compared with all other locations, with more males greater than 115 mm carapace width.…”

“…MPAs have been established worldwide, and their effects on species assemblages and diversity (Barrett, Buxton, and Edgar, 2009;Bell, 1983;Holland and Schnier, 2006;Lipej, Bonaca, and Sisko, 2003), fisheries productivity (Alcala et al, 2005;Gell and Roberts, 2003;Goni, Quetglas, and Renones, 2006;Hart, 2006;Roberts et al, 2001), and population characteristics of a variety of fish (Le Port, Lavery, and Montgomery, 2012;Macpherson, Garcia-Rubies, and Gordoa, 2000) and invertebrates (Barrett, Buxton, and Edgar, 2009;Branch, and Odendaal, 2003;Jack and Wing, 2010;Leite et al, 2009) have been well studied. Although the positive effects of MPAs are not universal (Edgar et al, 2014), the benefits of MPAs to individual species as a result of reduced fishing effort include increased abundance (Curley et al, 2013;Golbuu and Friedlander, 2011;Jack and Wing, 2010;Moland et al, 2013) and body size (BeukersStewart et al, 2005;Bevacqua et al, 2010;Branch and Odendaal, 2003;Pillans et al, 2005), particularly of reproducing adults, suggesting MPAs can enhance the reproductive capacity of species they protect (Kaiser et al, 2007). Assessing the influence of MPAs on particular species often involves comparisons of population characteristics or life history traits of organisms inside an MPA with those outside the MPA.…”