WWF Cover photo - Soufriere Marine Management Association ...

species of snappers and grouper are being eliminated by over-fishing throughout the Caribbean (Sadovy 1993,Heyman et al. 2001, Sala et al. 2001). Reserves that protect aggregation sites could significantly reduce overallfishing mortality. In the U.S. Virgin Islands, protection of a spawning aggregation site for Red Hind grouper,Epinephelus guttatus, has led to swift increases in average fish size and an increase in the availability of males inthis hermaphroditic species (Beets and Friedlander 1999), despite covering just 1.5% of the fishing grounds(Bohnsack 2000). There is new evidence that species like cod may home to specific coastal spawning sites andwould benefit from reserve protection in a similar way (Begg and Marteinsdottir 2000, J.A. Hutchings, pers.comm.). Even highly migratory species, like sharks, tuna and billfish, could benefit from reserves targeted toplaces where they are highly vulnerable, such as nursery grounds, spawning sites or aggregation sites likeseamounts (Norse et al. in press).Reserves could also be used to protect migration routes, such as that for female blue crabs, Callinectessapidus, in Chesapeake Bay in the USA (Lipcius et al. 2001b). At present only their spawning area at the mouthof the bay is protected from fishing. Lipcius et al. (2001b) conclude that while this closure protects 11-22% ofthe spawning stock, this is below the level recommended for sustainable exploitation (28%). Lipcius et al.(2001b) propose an expansion of the sanctuary to include a deep-water migration route taken by females to reachspawning sites. This would have the advantage of protecting a sufficient fraction of the spawning stock while thefishery could target mainly males and younger crabs in shallower water.Shipp’s (2002) analysis fails to take into account any effects of habitat protection in reserves on thebehaviour of species. There is a rich literature documenting how animal movement, social, reproductive andforaging behaviours are all influenced by habitat characteristics and food availability (e.g. Stephens and Krebs1986, Krebs and Davies 1993). Animals respond to their surroundings and behaviours are not immutable overtime. As habitats change and populations respond to protection, behavioural changes are inevitable. For example,following protection of the Leigh Marine Reserve in New Zealand, a fish species previously thought to besolitary began adopting haremic behaviour as their densities increased (Ballantine 1991). Improvements inhabitat in reserves, such as increasing structural complexity and prey densities in areas previously trawled(Bradshaw et al. 1999, 2002), will likely increase growth and survival of animals present there (Lindholm et al.1999). Reserves may also change previous behaviour patterns; for example, migratory species may spend longerin protected areas to take advantage of enhanced feeding conditions. Although not a migratory species, thecoelacanth provides a possible example of just such an effect. In the St. Lucia marine reserve in South Africa,coelacanths occur in depths of 80-100m, much shallower than in other places. There is speculation that high preydensities in the reserve allow the fish to forage shallower than in places that are heavily exploited by artisanalfisheries, like the Comoros Islands (Plante et al. 1998, C. Attwood pers. comm.). As the number of long-termstudies of reserves grows, we can expect to see more evidence showing that fishing not only reduces speciesdensities, but also alters their behaviour.Real reserves and fishery closures have already demonstrated benefits for fishery species as diverse asshellfish (Wallace 1999, Murawski et al. 2000), squid (Sauer 1995), crustaceans (Kelly et al. 2000, Rowe 2002),ascidians (Castilla 1999), and fish of a wide range of mobilities (Willis et al. 2001, Wantiez et al. 1997, Hollandet al. 1993, 1996, Murawksi et al. 2000). Few reserves have yet been designed to benefit highly migratoryspecies, but such animals could benefit from protection (Norse et al. in press). Models suggest reserves targetedto places of high stock vulnerability can protect spawning stocks and even enhance catches (Apostolaki et al.2002, Roberts and Sargant 2002). Contrary to claims by some critics (Shipp 2002), we conclude there arereserve designs that will offer some benefit to almost all species, with widely ranging species needingsupplementary management outside reserves.6. What is the evidence that fishery catches benefit from reserves?It is evident from the foregoing account that the precondition for fishery benefits has been met: spawning stocksdo build up in reserves. But do these gains translate into greater catches? Studies of fishery closures providedearly evidence that year-round protection, or even seasonal protection, could increase yields. For example, inJapan, a 13.7km 2 area was closed to all fishing to protect Zuwai (Tanner) crab (Chionoecetes opilio) in 1983(Yamasaki and Kuwahara 1990). Fisheries had been in decline for this species, partly due to by-catch mortalityof juveniles in the unselective seine fishery, and in fish trawls. The closure was located at an average depth of270m in an area where female crabs aggregated to mate each August to November. Over four years the closureincreased the fraction of large male crabs in the area from 10 to 42%. CPUE data from experimental fishing inthe closed area indicated an increase in crab densities over time. By the end of the study, seine vessels had begunconcentrating fishing effort around the refuge and boats close to the refuge generally achieved higher catches oflarge male crabs (the fishery is entirely for males). Tagging showed that crab movements regularly tookindividuals from the refuge into fishing grounds, thereby supplying the fishery through spillover (Yamasaki andKuwahara 1990).11