Leber et al Marine stock-enhancement potential in nursery habitats of Mugil cephalus 



457 



Kaneohe Bay in 1991 as part of a previous pilot study 

 (Leber et al. 3 ). Tags from 39 (1.3%) of the recaptured 

 fish were lost during the extraction process. These 

 39 cultured fish were released either in 1991 or 1992 

 but could not be further identified and were excluded 

 from our analyses. Thus, the decoded tag data are 

 based on 2,946 tags. 



Tag retention in the subsampled fish held for 4 

 months averaged 97.9% (±0.6 SE, n=12 tanks). With 

 one exception (92.6%, lot 1, lagoon release), all tag 

 retention rates within release lots exceeded 97%. 

 After capture data were adjusted for the 2.1% tag 

 loss, a total of about 2,697 cultured fish from the 1992 

 releases were actually captured (3.3% of the 80,507 

 fish released in this study). 



Tagged cultured fish represented about 50% of the 

 5,732 wild and cultured mullet collected from the four 

 study sites (Table 2). Proportions of cultured mullet 

 in Kahaluu samples remained >50% of the total (wild 

 and cultured) mullet sampled in collections through- 

 out the study and were >70% in six often collections 

 (Table 2 ). Proportions of hatchery fish were also high 

 at two streams north of the release site. 



Recovery of yearlings released in 1991 



Sampling periods in the present study ranged from 

 47 weeks to 100 weeks after the 1991 releases. Most 

 (86%) fish from 1991 releases were collected at 

 Kaneohe Stream, where they represented a high pro- 

 portion of 1-yr-old mullet at that site throughout their 

 second year in the wild (Table 3). Only 42 of the 304 

 fish from the 1991 release were collected outside 

 Kaneohe Stream. These 42 fish accounted for <3% of 



the cultured fish collected at any other site. Thus, 

 some fish from 1991 releases continued to occupy 

 juvenile mullet nursery habitats well into their sec- 

 ond year. 



Marine enhancement impact: 1992 releases 



Release impact in nursery habitats About 90% of 

 the 2,946 tags recovered and decoded were from 

 striped mullet released at Kahaluu in 1992. These 

 fish made a substantial contribution to juvenile re- 

 cruitment in three nursery habitats in the north end 

 of the bay: Kahaluu Stream, Kaalaea Stream, and 

 Waiahole Stream (Table 2). 



Impact of the test release was greatest at the re- 

 lease site, Kahaluu Stream; there was a trend to- 

 wards reduced impact with shoreline distance away 

 from that site. Cultured fish consistently outnum- 

 bered wild fish at the release site and averaged 66% 

 of the mullet in monthly collections at Kahaluu. Af- 

 ter 11 months in the wild, cultured fish still repre- 

 sented 50% of the mullet sampled at Kahaluu. Great- 

 est impact outside of the release site was seen at 

 Kaalaea, 1 km north of Kahaluu Stream, where cul- 

 tured fish averaged about 50% of the mullet sampled. 

 A substantial effect was also apparent in Waiahole 

 Stream, a mullet nursery habitat 3 km north of 

 Kahaluu Stream, where cultured fish averaged 28% of 

 the mullet sampled. Proportions of cultured mullet in 

 collections were stable through time at all four nurs- 

 ery habitats sampled until spring, when annual recruit- 

 ment of wild mullet began. Numbers of both wild and 

 cultured fish from the 1992 year class declined in 

 samples in spring at all nursery sites (Table 2). 



Table 3 



Movement patterns following 1991 releases of 91,245 tagged cultured mullet in Kaneohe Bay (half at Kahaluu Stream, half at 

 Kaneohe Stream. ) Release season and release site are identified for 304 tagged fish recovered at the various collection (recapture) 

 sites throughout the Bay. Recapture sites (and distances travelled) are ordered geographically within collection dates, from the 

 northernmost site (Waiahole Stream) to the southernmost site (Kaneohe Stream) at which tagged fish were collected (see Fig. 1). 

 Data are totals (n) recaptured in 300 cast-net samples per site taken over the 10-mo. study period. 



