Leber et al.: Marine stock-enhancement potential in nursery habitats of Mugil cephalus 455 



the three largest size intervals were released in sum- 

 mer (none <70 mm TL). There was size variation in 

 all batches of mullet reared for this study. However, 

 the primary difference among the five size intervals 

 offish released was fish age. 



Replicate release lots were introduced biweekly for 

 a 3- to 4-week period in both spring and summer. 

 Fish were transported and then released simulta- 

 neously at the stream inlet and 300 m upstream in a 

 10-ha lagoon. Numbers of tagged and released fish 

 varied between seasons and among size intervals 

 released but were held nearly constant among re- 

 lease lots and between release sites (Table 1). Be- 

 tween 10,200 and 15,100 tagged fish were released 

 in each of six release lots. Releases were conducted 

 around mid-day or early afternoon. Bottom salini- 

 ties at release sites ranged from 12 to 25 ppt. All 

 releases were made near the shoreline in water from 

 0.5 to 1.5 m deep. 



Previous studies revealed a CWT retention rate of 

 97% for striped mullet during 12 months following 

 tagging (Oceanic Institute 4 ). To verify tag-retention 

 rates in this study, at least 59c offish tagged for each 

 release lot were randomly subsampled prior to each 

 release. These subsamples, totalling 4,264 tagged 

 fish, were retained in 12 tanks for up to 4 months; 

 fish were checked monthly to verify when 9c tag re- 

 tention stabilized (Blankenship, 1990). 



Tagged fish from the 1991 study were also recov- 

 ered in this study. Methods in that study were es- 



sentially identical to those here, with two exceptions: 

 1) in 1991, fish of all five size intervals were released 

 in both spring and summer; 2) 1991 release sites in- 

 cluded Kahaluu Stream mouth and Kaneohe Stream 

 mouth (Leber et al. 3 ). The mouth of Kaneohe Stream 

 lies 11.6 km south of Kahaluu Stream mouth. 



Monitoring 



To evaluate the effect of releases on juvenile abun- 

 dance, collections were made monthly with cast nets 

 in four Kaneohe Bay nursery habitats, except for July 

 (when summer releases were conducted). We began 

 to monitor abundances of released and wild striped 

 mullet in Kaneohe Bay on 8 June 1992 and contin- 

 ued to do so for 10 months. Each field collection was 

 conducted during a 1-wk period. Collections were 

 made during the day during an 8-h period at each 

 nursery site (sampling station). Stations were estab- 

 lished in the vicinity of documented striped mullet 

 nursery habitats at various tributaries throughout 

 the bay (Oceanic Institute 4 ). 



To standardize collection effort, two substations 

 were established at each station — one 200 to 300 m 

 upstream, the other in the bay seaward of the stream 

 mouth and on subtidal reef flats running along the 

 bay shore on both sides of the stream mouth. Within 

 substations, 15 cast-net throws were made. A total 

 of 120 cast-net samples were taken each month. To 

 broaden the range of microhabitats and fish size- 



Table 1 



Summary statistics for 80,507 fish tagged and released in 1992 to evaluate hatchery releases in Kaneohe Bay. Unique batch codes 

 were used to identify fish from each cell in the matrix. Spring release lot 1 occurred on 4 May, lot 2 on 15 May, and lot 3 on 29 May. 

 Summer release lot 1 occurred on 13 July, lot 2 on 24 July, and lot 3 on 7 August. 



Release season 



Release 

 site 



Size at 

 release 



Spring release lot 



Summer release lot 



Total 



Grand 



Total total 



Kahaluu (upstream at lagoon) 45-60 mm 



60-70 mm 

 70-85 mm 

 85-110 mm 

 110-130 mm 



Subtotal 



Kahaluu Stream (mouth i 



45-60 mm 

 60-70 mm 

 70-85 mm 

 85-110 mm 

 110-130 mm 



Subtotal 



2,356 



2,372 



1,595 



807 



398 



7,528 



2,356 



2,361 



1,596 



806 



396 



7,515 



2,368 



2,375 



1,594 



807 



399 



2,277 



2,371 



1,591 



805 



399 



7,543 7,443 



2,369 



2,370 



1,593 



806 



399 



7,537 



2,321 



2,344 



1.599 



805 



399 



7,468 



7.001 

 7,118 

 4,780 

 2,419 

 1,196 



22,514 



7,046 

 7,075 

 4,788 

 2,417 

 1,194 



22,520 











2,867 



2,863 



250 



5,980 











2,878 



2,848 



249 



5,975 











2,497 



2,493 



125 



5,115 



ii 







2,494 



2,500 



125 



5,119 









 4,063 

 2,540 



72 



6,675 











4,069 



2,540 







6,61)9 



II 







9,427 



7.896 



447 



17,770 









 9,441 



7.KS.S 



374 



17,703 



Grand total 



7,001 



7,118 



14,207 



10,315 



1,643 



40,284 



7,046 



7,075 



14.229 



10,305 



1,568 



40,223 



15.043 15,080 14,911 45,034 11,955 10,234 13,284 35,473 80,507 



