Identification of Habitat of Juvenile 

 Snappers in Hawaii 



Deepwater snappers have high commercial and 

 recreational value throughout the tropics, and 

 their fisheries and species biology have been 

 widely studied. However, little is known about 

 the ecologj' of the juveniles between settlement 

 to the demersal habitat and recruitment to the 

 adult population (Munro 1987). In Hawaii, no 

 information regarding location, size, or habitat 

 of juvenile lutjanids has emerged after more 

 than a decade of concentrated studies of adult 

 stocks (Ralston 1980; Humphreys 1986). The ab- 

 sence of observations and collections of juvenile 

 lutjanids or of their occun-ence as prey items in 

 the adult habitat suggests that they settle else- 

 where prior to recruitment. 



Adult snappers have been frequently reported 

 as being associated with structural relief at 

 depths of 100-500 m (Parrish 1987). In contrast, 

 juveniles have not been caught or visually ob- 

 served in such habitats in surveys made with 

 scuba or submersible vehicles (Ralston et al. 

 1986; Moffitt et al. 1989). Owing to the lack of 

 conventional scientific evidence about the habi- 

 tat of juveniles, occasional reports of juveniles 

 captured by shallow-water recreational fisher- 

 men in Hawaii continued to go largely unnoticed 

 by researchers until one angler brought back live 

 juvenile specimens of both Pristipomoides 

 filanie)itosus and Aprion viresceus in Septem- 

 ber 1988. This tangible evidence provided the 

 stimulus to conduct some exploratory fishing in 

 relatively shallow waters and to attempt to visu- 

 ally observe the fishes' habitat. This report sum- 

 marizes the results of that investigation. 



Methods 



During October 1988, the bottom was fished 

 and observed with scuba at three stations off the 

 eastern side of the Hawaiian Island of Oahu. 

 Stations 1 and 2, separated by 2 km along the 

 coast, were situated outside the barrier reef and 

 between the two main entrance channels of 

 Kaneohe Bay; station 3 was located southeast of 

 Mokapu Peninsula in Kailua Bay (Fig. 1). Most 

 fishing was done in midmorning (0800-1200). At 

 station 3, one afternoon and evening sampling 

 was taken in addition to the morning sampling. 



A single day of intensive fishing was done at 

 each station from a small boat with two lines, 

 each bearing three No. 10 circle hooks baited 



Manuscript accepted .June 1989. 



Fishery Bulletin, U.S. 87:1001-100.5, 1989. 



with live shrimp. Fishing was limited to depths 

 of 31-76 m, to allow observation of habitat by 

 scuba. At each station, the boat drifted or occu- 

 pied sequential, anchored positions along a tran- 

 sect across the bottom contours while the fishing 

 lines were bounced off the bottom. The depth 

 was measured periodically during fishing and 

 immediately following the landing of juvenile 

 bottom fishes. 



Habitat observations with scuba were per- 

 formed at the three stations on mornings soon 

 after the samphng was completed, at the loca- 

 tions and depths where target species had been 

 caught earlier. Fishing with a single line helped 

 confirm observation locations on two occasions: 

 target species were landed immediately before 

 or during the dive. At least two dives were made 

 at each station, one or more in shallow (40-50 m) 

 and the other in deep (51-76 m) water. At sta- 

 tions yielding no fish in either depth range, ob- 

 servations were conducted at depths similar to 

 those yielding fish at the other stations. With the 

 exception of the 52 m dive at station 2, dives in 

 the deep ends of the transects occurred at what 

 proved to be the most productive fishing depths 

 (>61 m). Restricted bottom time at these depths 

 limited diving activities to observing habitat and 

 scanning an area of about 6,000 ni" for target 

 species. 



Additional specimens were concurrently col- 

 lected from waters off Lahilahi Point on western 

 Oahu by the same methods, except that artificial 

 bait was used on a single line and depth was only 

 estimated (60-90 m) by the amount of hne de- 

 ployed. Stomachs and hindguts of P. filanien- 

 tosus from all sources were examined, and prey 

 items were counted and roughly classified. The 

 P . filamentosus containing food items were used 

 in the analysis of occurrence (prey type as a 

 percentage of all individuals eaten) and fre- 

 quency (percentage of fish containing each prey 

 type). 



Results and Discussion 



A total of 36 juvenile lutjanids were collected 

 from the three stations (Table 1). Pristi- 

 poinoides filcnite)itosus (h = 30) were caught at 

 all three stations, all at 61-73 m depths; 25 were 

 captured at station 1. Five Aprion virescens and 

 the one Aphareus rutilans were taken at station 

 2 at 40 m. At stations 1 and 2, the catch rate 

 consistently dechned at all depths in the late 

 morning hours. At station 3, no fish were caught 

 until dusk, when four P. filamottosus were 



1001 



