A comparison of larval and 

 postlarval gulf menhaden, 

 Brevoortia patronus, growth rates 

 between an offshore spawning 

 ground and an estuarine nursery 



Richard C. Raynie* 

 Richard F. Shaw 



Coastal Fisheries Institute 

 Louisiana State University 

 Baton Rouge, Louisiana 70803 



The fishery for gulf menhaden, 

 Brevoortia patronus, was the larg- 

 est by weight in the United States 

 from 1963 through 1988 and has 

 had a significant impact on the 

 economy of the northern Gulf of 

 Mexico coast. The species is also an 

 ecologically important prey item for 

 a number of commercially and 

 recreationally important species 

 (Lassuy, 1983). 



Gulf menhaden early life history 

 has been reviewed by a number of 

 authors (Lassuy, 1983; Deegan, 

 1985; Powell and Phonlor, 1986; 

 Shaw et al., 1988; Christmas and 

 Waller 1 ). Adults spawn in offshore 

 and coastal waters in depths rang- 

 ing from 11 to 128 m; peak spawn- 

 ing occurs between the 10- and 60- 

 m isobaths (Shaw et al., 1988). 

 Most spawning generally occurs 

 between October and March; peak 

 spawning occurs in December 

 (Fore, 1970; Shaw et al., 1985; 

 Christmas and Waller 1 ). Once 

 spawned, gulf menhaden eggs are 

 pelagic and hatch within about two 

 days. The offshore larval drift pe- 

 riod may last from 4 to 10 weeks 

 (Deegan and Thompson, 1987; 

 Shaw et al., 1988). Peak immigra- 

 tion through tidal passes into es- 

 tuarine nurseries generally occurs 



890 



between December and March 

 (Suttkus, 1956; Lassuy, 1983). 



In the estuary, larval gulf men- 

 haden move into bayous and other 

 low salinity areas at the onset of 

 transformation into juveniles (Fore 

 and Baxter, 1972; Simoneaux, 

 1979; Deegan, 1990; Raynie and 

 Shaw, in press). Estuarine resi- 

 dence is typical during summer 

 months. As juveniles grow larger, 

 they tend to move downstream to 

 higher salinity waters and from 

 late summer to winter many emi- 

 grate to open coastal waters (Dee- 

 gan, 1990). 



Daily otolith increment forma- 

 tion has been validated and is esti- 

 mated to begin at the onset of ex- 

 ogenous feeding, which occurs 

 about three days after hatching 

 (Warlen, 1988). Growth rate esti- 

 mates based on larval gulf menha- 

 den otolith analyses have been 

 made from larvae collected off the 

 Mississippi River Delta, Florida 

 and Texas (Warlen, 1988) and from 

 young of the year collected within 

 estuarine waters of Louisiana 

 (Deegan and Thompson, 1987). A 

 comparison between growth rates 

 of gulf menhaden captured from 

 continental shelf and adjacent es- 

 tuarine waters during the same 



time period has not been done. The 

 purpose of this paper is to examine 

 growth rates of larval and postlar- 

 val gulf menhaden from offshore 

 and estuarine habitats and relate 

 the results to metamorphosis. 



Materials and methods 



Sampling procedure 



Gulf menhaden larvae and post- 

 larvae were collected at two sta- 

 tions in the northern Gulf of Mexico 

 (6 and 32 km from shore) on 23 

 January 1990 and from three loca- 

 tions (Lower Bay, Mosquito Island, 

 and Big Carencro Bayou) within 

 the adjacent estuary, Fourleague 

 Bay, Louisiana, on 24-25 January 

 1990 (see Raynie and Shaw, in 

 press). Larvae were collected off- 

 shore with a 60-cm bongo frame 

 equipped with a 505-um mesh net 

 fitted with a flow meter (General 

 Oceanics Model no. 2030). Within 

 Fourleague Bay, collections were 

 made with a bow-mounted plank- 

 ton push net of the same diameter 

 and mesh size as that used offshore. 

 One three-minute collection was 

 taken at each station offshore and 

 at each station each day within 

 Fourleague Bay. Plankton push 

 nets have been shown to be effec- 

 tive at collecting larval fish (Miller, 

 1973; Raynie and Shaw, in press) 

 and juvenile fish (Herke, 1969; 

 Kriete and Loesch, 1980). The use 

 of this gear in this highly turbid 

 and shallow estuarine system 

 (mean depth=1.5 m; Teague et al., 

 1988) minimizes net avoidance. 



Address correspondence to Louisiana De- 

 partment of Natural Resources, Coastal 

 Restoration Division, RO. Box 94396, Ba- 

 ton Rouge, Louisiana 70804-9396 

 1 Christmas, J. Y., and R. S. Waller. 1975. 

 Location and time of menhaden spawn- 

 ing in the Gulf of Mexico. CCRL/NMFS 

 Contract Rep. 03-4-042-24. 



Manuscript accepted 16 March 1994. 

 Fishery Bulletin 92:890-894. 



