452 



AbStraCt.-Declines in world fish- 

 ery landings have prompted new inter- 

 est in the use of cultured fishes to help 

 replenish depleted fish populations. 

 The hypothesis that hatchery releases 

 can increase population size has at 

 least two corollaries that need to be 

 tested: 1 ) released cultured fish survive, 

 grow, and contribute to recruitment; 

 and 2) cultured fish do not displace wild 

 stocks. The former corollary is consid- 

 ered here for striped mullet, Mugil 

 cephalus L., in nursery habitats. 



Results from pilot experiments were 

 used to modify release strategies to test 

 marine stock enhancement potential in 

 Kaneohe Bay, Hawaii. Of 80,507 na- 

 tive, cultured, striped mullet finger- 

 lings tagged with coded wire and re- 

 leased during spring and summer, 

 2,642 fish were recovered by cast-net 

 sampling during 11 months. Recapture 

 rate increased 600% compared with ini- 

 tial studies in Kaneohe Bay. This in- 

 crease was the result of confining re- 

 leases to the vicinity of fresh-water 

 streams and of imposing a minimum 

 size of 70 mm TL during summer re- 

 leases. After 11 months, cultured fish 

 represented 50% of the striped mullet 

 in collections at the release site, 20% 

 in a nursery habitat 1 km to the north, 

 and 10% in a nursery 3 km north. The 

 location of releases (stream mouth vs. 

 upstream lagoon) significantly affected 

 dispersal patterns but did not affect 

 growth or recapture rate. This study 

 corroborated earlier results which 

 showed that the smallest fish released 

 (45-60 mm) could survive relatively 

 well if released in spring. At least three 

 measures were needed to describe 

 hatchery effect: 1) hatchery contribu- 

 tion (% cultured fish in samples), 2) 

 catch per unit of effort for cultured and 

 wild striped mullet, and 3) recovery 

 rate (no. captured/no. released). This 

 study documents that survival of cul- 

 tured fish in coastal nurseries can be 

 significantly improved by using infor- 

 mation from pilot release experiments 

 to revise release parameters. 



Marine stock-enhancement potential in 

 nursery habitats of striped mullet, 

 Mugil cephalus, in Hawaii 



Kenneth M. Leber 

 Steve M. Arce 

 David A. Sterritt* 

 Nathan R Brennan** 



The Oceanic Institute 

 Makapuu Point 

 Waimanalo, Hawaii 96795 



Manuscript accepted 9 January 1996. 

 Fishery Bulletin 94:452-471 (1996). 



The need for improved understand- 

 ing and management of coastal fish- 

 eries is clear (New, 1991; NMFS, 

 1991, 1992; Anthony, 1993; Sissen- 

 wine and Rosenberg, 1993; Schnute 

 and Richards, 1994). In 1990, 

 growth in annual world fishery pro- 

 duction peaked at 100 million met- 

 ric tons (t) (FAO, 1992). Without 

 more effective control of marine 

 fisheries, seafood availability and 

 recreational fishing opportunities 

 are likely to decline at a rapid pace 

 as demand increasingly outweighs 

 supply during the next century 

 (New, 1991; FAO, 1992). Ricker 

 (1969) estimated maximum sus- 

 tainable annual production levels of 

 wild fisheries may be limited to 160 

 million t. More recently, the Food 

 and Agriculture Organization of the 

 United Nations (FAO) revised the 

 estimate to 100 million t (WRI, 

 1990). Larkin (1993) suggests that 

 sea farming could increase annual 

 yields several fold over this level. 



One form of sea farming, supple- 

 menting wild stocks with releases 

 of cultured organisms (hatchery- 

 based stock enhancement), may 

 have considerable potential in ma- 

 rine and estuarine environments. 

 Whether stock enhancement can 

 help significantly increase world 

 production levels of seafood is un- 

 clear (Schnute and Richards, 1994; 

 Smedstad et al., 1994). Increased 



emphasis on quantitative evalua- 

 tion is needed to determine the ac- 

 tual potential of stock enhance- 

 ment. Norway and the United 

 States first conducted large-scale 

 hatchery releases of yolk-sac larvae 

 of marine fishes at the end of the 

 last century (Solemdal et al., 1984; 

 Grimes, 1995); Japan followed with 

 releases of hatched larvae of cod, 

 herring, and king crab in the early 

 1900's (called "sea farming" in Ja- 

 pan; Kitada et al., 1992; Honma, 

 1993). A century later, the central 

 issue remains largely unresolved — 

 can propagation and release of cul- 

 tured marine organisms into the wild 

 increase coastal fish populations? 



Although marine stocking pro- 

 grams in the USA were abandoned 

 earlier this century for lack of a 

 clear impact on fisheries landings, 

 the potential for using hatchery re- 

 leases to increase populations of 

 coastal fishes was never critically 

 tested (Richards and Edwards, 

 1986). Now, modern marking meth- 

 ods and new aquaculture capabili- 



* Present address: Point Whitney Shellfish 

 Laboratory, Washington Department of 

 Fish and Wildlife, 1000 Point Whitney 

 Road, Brinnon, WA 98320. 

 ** Present address: Tennessee Technological 

 University, Tennessee Cooperative Fish- 

 ery-Research Unit, P.O. Box 5114, Cooke- 

 ville, TN 38505. 



