Abstract. — Gonad-somatic in- 

 dex (GSI), the relation of ovarian to 

 somatic weight, was calculated for 

 14 species of finfish that are yearlong 

 residents of the New York Bight. 

 Specimens were collected monthly 

 from June 1974 through June 1975 

 in the ocean and associated estuarine 

 waters of the Bight. Analysis indi- 

 cated that alewife and yellowtail 

 flounder are spring spawners; silver 

 and red hake, black sea bass, butter- 

 fish, striped and northern searobin, 

 and fourspot flounder are summer 

 spawners; and summer and winter 

 flounder are fall-winter spawners. 

 Offshore hake e.xliibited a protracted 

 spawning season with ripe females 

 collected from spring through fall, 

 while spotted hake and windowpane 

 exhibited bimodal spawning patterns 

 with two GSI peaks per year. Tl'ke 

 co-occurrence of spawning with ap- 

 propriate food supply and environ- 

 mental conditions is discussed on an 

 individual-species as well as species- 

 complex basis. 



Annual Cycles of Gonad-Somatic 

 Indices as Indicators of Spawning 

 Activity for Selected Species of 

 Finfish Collected from the 

 Mew York Bight 



Stuart J. Wllk 

 Wallace W. Morse 

 Linda L. Stehlik 



Sandy Hook Laboratory, Northeast Fisheries Science Center 



National Marine Fisheries Service, NOAA, Highlands, New Jersey 07732 



Manuscript accepted 10 July 1990. 

 Fishery Bulletin, U.S. 88:775-786. 



In temperate zones, reproduction of 

 marine fish species is usually char- 

 acterized by single annual peaks of 

 spawning activity (Gushing 1969). 

 Seasonal changes in the gonads of 

 fishes, in preparation for reproduc- 

 tion, are known to be controlled by 

 hormones, and triggered, sometimes 

 well in advance of spawning, by 

 photoperiod (Hoar 1969, Bye 1984). 

 Minor variations in spawning time, 

 during any given year, are believed 

 to be related to temperature and to 

 the overall condition of the fish (de 

 Vlaming 1972, Bye 1984). Wootton 

 (1984) defines reproductive "strate- 

 gies" as the genetically determined 

 pattern of spawning behavior, and 

 reproductive "tactics" as the re- 

 sponses to exogenous cues during a 

 single season. 



The gonad-somatic index (GSI), the 

 relation of ovarian weight to somatic 

 weight, provides a measure of spawn- 

 ing readiness while removing vari- 

 ability attributable to fish size (Nikol- 

 skii 1963). The GSI has also been 

 termed the gonosomatic index (de 

 Vlaming et al. 1982) and maturity in- 

 dex (Morse 1981). Annual cycles in 

 GSI can be thought of as an approx- 

 imate measure of the energy ex- 

 pended for reproduction, which 

 makes this information critical in for- 

 mulating energy budgets relating to 

 the balance between fish production 

 and consumption. 



Approximate spawning times for 

 the most common species which oc- 

 cur in the New York Bight have been 

 established based on the distribution 

 of eggs and larvae (Colton et al. 1979) 

 and published life-history information 

 (Grosslein and Azarovitz 1982). How- 

 ever, detailed qualitative and quan- 

 titative information on annual cycles 

 of spawning as determined by exam- 

 ination of maturity stages is lacking 

 for many, if not most, of these same 

 species. This study presents monthly 

 variations in GSI as they relate to 

 hydrographic observations for 14 spe- 

 cies of fish which represent many of 

 the dominant fishes found on the Mid- 

 dle Atlantic continental shelf and in 

 associated estuarine waters (WOk and 

 Silverman 1976ab, Wilk et al. 1977; 

 Colvocoresses and Musick 1984). 



Materials and methods 



Fish were collected from June 1974 

 to June 1975 during monthly bottom 

 surveys in the central portion of the 

 New York Bight at the confluence of 

 the Long Island, New York and New 

 Jersey coastlines and the contiguous 

 Sandy Hook-Lower-Raritan Bay es- 

 tuary (Fig. 1). This area is character- 

 ized by seasonally intensive recrea- 

 tional and commercial fisheries and 

 is influenced by a wide variety of an- 

 thropogenic activities (Gross 1976, 

 Mayer 1982). 



775 



