360 



Abstract — The contribution of the no- 

 take marine reserve at Apo Island, 

 Philippines, to local fishery yield 

 through "spillover" (net export of 

 adult fish) was estimated. Spatial 

 patterns of fishing effort, yield, and 

 catch rates around Apo Island were 

 documented daily in 20C3-2004. 

 Catch rates were higher near the 

 reserve (by a factor of 1.1 to 2.0), but 

 fishing effort was often lowest there. 

 Higher catch rates near the reserve 

 were more likely due to spillover than 

 to low fishing intensity. Lower fishing 

 effort near the reserve may have been 

 due to 1) weather patterns, 2) tra- 

 ditional importance of other fishing 

 grounds, 3) high variability in catch 

 rates, 4) lower market value of target 

 species, and 5) social pressures. The 

 yield taken near the reserve was only 

 10% of the total yield, but the actual 

 spillover contribution was probably 

 much less than this. This study is one 

 of the few to estimate the spillover 

 contribution to overall yield and to 

 document the responses of fishermen 

 to spillover. 



How much does the fishery at Apo Island 

 benefit from spillover of adult fish from 

 the adjacent marine reserve? 



Rene A. Abesamis'- ^ 



Angel C. Alcala^ 



Garry R. Russ^ 



' School of Marine Biology and Aquaculture 

 James Cook University 

 Townsville, Queensland 4811, Australia 

 E-mail address (for G R Russ, contact auttior) garry russm'icu edu au 



^ Silliman University Angelo King Center for Research and Environmental Management 

 Silliman University 

 Dumaguete City 6200, Philippines 



Manuscript submitted 5 November 2004 

 to the Scientific Editor's Office. 



Manuscript approved for publication 



20 September 2005 by the Scientific Editor. 



Fish. Bull. 104:360-375 (2006). 



No-take marine reserves (areas closed 

 to fishing) are now often established 

 with an objective of sustaining or 

 enhancing fisheries (Gell and Roberts, 

 2003). Reserves could achieve such 

 objectives by eventually becoming net 

 exporters of adult biomass, defined as 

 "spillover," and by providing net larval 

 export, known as the "recruitment 

 effect" (Russ, 2002). Fisheries will 

 probably benefit from spillover in a 

 minor way only. Theoretical studies 

 have indicated that potential fishery 

 yield (yield per recruit) from spillover 

 would be insignificant, if any yield at 

 all, except when stock abundance out- 

 side reserves is very low due to high 

 fishing mortality (Polacheck, 1990; 

 Russ et al., 1992; DeMartini, 1993). 

 Thus, potential gains from spillover 

 are predicted to be only moderate. 

 There seems to be general agree- 

 ment that the more important fishery 

 enhancement effect of reserves would 

 be due to net larval export (Carr and 

 Reed, 1993; Russ, 2002). However, the 

 establishment of reserves, particu- 

 larly in developing countries, requires 

 strong support from local stakehold- 

 ers, especially fishermen (Russ and 

 Alcala, 1996; Galal et al., 2002). 

 There is a concern that, in some cases, 

 support for reserves may be difficult 

 to obtain on the pretext of enhanced 

 fisheries through increased recruit- 

 ment (Russ and Alcala, 1996). Net 

 larval export may seem less convinc- 

 ing to fishermen because of the broad 

 spatial scale (tens to hundreds of kilo- 



meters) at which it will probably occur 

 (Russ and Alcala, 1996; Russ, 2002). 

 Yields from spillover, although prob- 

 ably small, may play a critical role 

 in convincing fishermen to support 

 establishment and maintenance of 

 reserves (Russ and Alcala, 1996). For 

 some fishermen, adult fish "spilling- 

 over" from reserves, especially in the 

 case of larger fish, will appear to be a 

 more direct and tangible benefit than 

 larvae recruiting to fishing grounds 

 from distant reserves. Thus, spillover 

 may have a substantial positive psy- 

 chological effect on the attitudes of 

 fishermen toward reserves. 



However, few empirical studies 

 have quantified the effects of spillover 

 on fishery yields, nor the responses 

 of fishermen to spillover, perhaps be- 

 cause some advocates of reserves are 

 sometimes overly optimistic about 

 the potential benefits of spillover. 

 Two studies in one location in Ke- 

 nya showed that after several years 

 of reserve protection, spillover was 

 not enough to compensate for reduc- 

 tion of total yield due to the creation 

 of a large no-take reserve (McClana- 

 han and Kaunda-Arara, 1996; Mc- 

 Clanahan and Mangi, 2000). The 

 reserve, Mombasa Marine Park, took 

 away 50-60% (-6-8 km^) of the total 

 fishing area. In this case the reserve 

 probably occupied too large an area 

 to supplement total fishery yield sub- 

 stantially (McClanahan and Mangi, 

 2000). However, in other countries, 

 no-take reserves as large as Mombasa 



