Spillover and recruitment effects

14.3.1 Spillover and recruitment effects

In contrast to the number of studies on abundance and size effects, few studies have addressed the movement of target species across the boundaries of MPAs (Table 14.3). Spatial differences in size and abundance have been used to infer movement, but tagging and tracking can alone indicate, the extent and direction of movements. Holland et al. (1993, 1996) used both to infer the extent of movement by the trevally (Caranx melampygus) and goat- fish (Mulloides flavolineatus) in and out of the MPA around Coconut Island, Hawaii. Funicelli

Table 14.3 Movement of target species in and out of MPAs (* = no movement across MPA boundary recorded, _ = movement in some species not others) and changes in overall fishery catch (increase, * = no change, _ = increase under some conditions, not others) of various marine fishery target

species in areas closed to fishing ( a = seasonal only) either in practice or inferred from simulation ( b = data from modelling only) in different parts of the world.

W. South

Australasia South America America

E. South

Caribbean

W. North

E. North

Western

Southern West

East

South Southeast East

Asia Pacific Spillover

Africa Africa

11. 26. – Marine Protected Areas Yield Fish

– – 1. Funicelli et al. 1988.

15. Bryant et al. 1989, Rutherford et al. 1989.

2. Holland et al. 1993, 1996.

16. Buxton and Allen 1989.

3. Klima et al. 1986, Gitschlag 1986.

17. Beinssen 1989b, 1990.

4. Borley et al. 1923, Margetts and Holt. 1948. 18. M. Corless, B. Hatcher, W. Hunte and S. Scott, unpublished data. 5. Garcia and Demetropoulos 1986.

19. Attwood and Bennet 1994.

6. DeMartini 1993.

20. Davies 1996.

7. Alcala and Russ 1990.

21. ICES 1990.

8. McClanahan and Kaunda-Arara 1996, T.R. McClanahan and

22. Bailey 1991.

S. Mangi, unpublished data 1999.

23. ICES 1999, Pastoors et al. 2000.

9. Sladek Nowlis and Roberts 1999.

24. Beverton and Holt 1957, Horwood et al. 1998.

10. Polacheck 1990, Guénette and Pitcher 1999.

25. Munro 1999.

11. Yamasaki and Kuwahara 1990.

26. Kelly 1999.

12. Klima et al. 1986.

27. Watson 1996.

13. Davis 1977, Davis and Dodrill 1980, 1989.

28. Daan 1993.

14. Chapman and Kramer 2000.

29. Quinn et al. 1993.

Chapter 14

et al. (1988) tagged mullet (Mugil cephalus), drums (Sciaenops spp.) and spotted seatrout (Cynoscion nebulosus ), while Rutherford et al. (1989) tagged grey snapper (Lutjanus griseus), to infer move- ments within and out of MPAs on the east coast of Florida. Other studies have demonstrated movements of decapods, including crabs in Japan (Yamasaki and Kuwahara 1990), and lobsters in Florida and New Zealand (Davis 1977; Davis and Dodrill 1980, 1989; Kelly 1999), and shrimp (Klima et al. 1986; Gitschlag 1986) in Florida. The evidence from such studies is that movement does occur across MPA boundaries, but that the distance over which it occurs routinely in reef- associated species tends to be small; most informa- tion indicates spatial scales of less than one kilo- metre. In other species, such as mullet (Funicelli et al. 1988), or most commercial species in the North Sea, it is evident that the spatial scale of movement can be much greater, although it should be noted that in reef species the scale of movement may be greater than indicated by the short-term studies above. This movement can occur in a variety of contexts, including home-ranging and foraging behaviour (Holland et al. 1996), spawning migration (Holland et al. 1993), and changes in habitat as animals get older (Parrish 1987). The distance range of movement in reef-associated species is similar to that of their home ranges, but such data probably do not include seasonal movements. These move- ments include those for spawning which occur over greater distances and may be important as the sus- ceptibility of species to fishing is likely to be greater in some species during spawning (Fulton et al. 1999).

The build-up in spawning biomass which oc- curs in site-attached species in MPAs may lead to greater egg output, but the consequences of this for recruitment are uncertain and there appear to be no data indicating greater availability of fish to any fishery as a result of the greater supply of larvae. Assuming a metapopulation structure such as may occur in some arrays of patch reefs over dis- tances of tens of kilometres, it is likely that MPAs will enhance yield especially when the fishing mortality is high (Man et al. 1995). In some cases, such as in the southeastern USA, the spawning stock biomass may be so depleted that recruitment

is stock dependent (Plan Development Team 1990; Ault et al. 1998) and will therefore tend to increase as biomass accumulates within MPAs, but clearly this will depend upon the species being relatively sedentary (e.g. DeMartini 1993). The actual range over which such recruitment can be expected to occur is a matter for debate. In a small number of marine fishes (e.g. the scorpaenid Sebastes and eelpout Zoarces) and invertebrates with direct de- velopment, or very limited planktonic lives, the range should be small, but in most cases the fish re- cruitment supported by MPAs maybe distributed over tens to hundreds of kilometres. The shape and orientation of the dispersal envelope will depend on species, season and other factors (Roberts 1997b). The larval longevity of most fishes is prob- ably best viewed as a measure of the range of dis- tances over which dispersal can occur, because of other factors, such as current speed and direction which will affect dispersal in practice (e.g. Carr and Reed 1993).