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Michael P. Seki 



Southwest Fisheries Center Honolulu 



Laboratory 

 National Marine Fisheries Service, NOAA 

 2570 Dole St. 

 Honolulu, HI 96822-2396 



Michael W. Callahan 



Hawaii Cooperative Fishery Research Unit 

 University of Hawaii 

 Honolulu, HI 96822 



SEASONALITY AND DEPTH DISTRIBUTION 



OF LARVAL FISHES IN 



THE NORTHERN GULF OF MEXICO 



ABOVE LATITUDE 26°00 N 



Justification and Methods 



Information on early life stages of fishes is impor- 

 tant for a better understanding of recruitment pro- 

 cesses and for the proper management of fisheries. 

 Knowledge of seasonal occurrence and depth dis- 

 tribution of larval fishes is essential for planning and 

 scheduling ichthyoplankton cruises (Colton et al. 

 1979) and juvenile surveys, so that sampling for 

 target species can be concentrated during periods 

 and at depths where effort will be most effective 

 (Saville 1964). In addition, knowledge of the seasonal 

 occurrence of early life stages is an important aid 

 in identifying larvae. Because eggs and yolk-sac lar- 

 vae are planktonic for only a relatively few days 

 after being spawned, the presence and distribution 

 of early life stages also suggests proximity of adult 

 spawning concentrations (Houde 1974), aiding the 

 definition of spawning areas and seasonal spawn- 

 ing migrations of adults. Since some commercial and 

 recreational fisheries (e.g., red drum, Sciaenops 

 ocellatus, and black drum, Pogonias cromis) exploit 

 spawning aggregations, encroachment on these 

 aggregations could have an adverse impact on the 

 fishery. 



Colton et al. (1979) summarized larval seasonality 

 data and spawning areas for marine continental 

 shelf fishes between Nova Scotia and North Caro- 

 lina; whereas, Herrema et al. (1985) inferred spawn- 

 ing seasons of coastal fishes off eastern Florida 

 based on examination of enlarged gonads. The sea- 

 sonal occurrence of larvae of many species from the 

 northern Gulf of Mexico (GOMEX), however, is not 

 well documented. The northern GOMEX is herein 

 defined as waters north of lat. 26°00'N; this area 

 approximates the U.S. Fishery Conservation (i.e.. 

 Exclusive Economic) Zone. For discussion, the study 

 area was subdivided into three regions (Fig. 1) based 

 on longitude as follows: eastern GOMEX (waters 

 east of long. 86°00'W), central GOMEX (those 

 between 86°00'W and 94°00'W), and western 

 GOMEX (waters west of 94°00'W). Seasonality data 

 are scattered throughout the grey literature, and 

 many studies have focused on either select taxa or 

 are limited in spatial or temporal coverage. The most 

 comprehensive studies of the larval ichthyofauna 

 community in the northern GOMEX were those of 

 Houde et al. (1979) from continental shelf waters 



FISHERY BULLETIN: VOL. 86, NO. 4. 1988. 



811 



