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Fishery Bulletin 88(4), 1990 



which drive cycles of productivity. An abundant source 

 of food must be available for adult fish to produce 

 stored fat for subsequent gamete production (de Vlam- 

 ing 1972). Plankton of the right size, density, and qual- 

 ity must be available to pelagic larvae at the critical 

 time of first feeding. As an example, the spawning of 

 yellowtail flounder corresponds to the spring increase 

 in zooplankton off southern New England (Sherman 

 et al. 1984). The maximum concentration of zooplank- 

 ton in the Middle Atlantic occurs from mid- to late- 

 summer which coincides with the peak concentrations 

 of larval searobins and butterfish as well as numerous 

 other species (Sherman et al. 1984). The fishes that 

 reproduce in the New York Bight during winter have 

 already accumulated fat reserves during the summer 

 and fall. Releasing eggs during winter may give a sur- 

 vival advantage to the larvae since many other fishes, 

 potential competitors and predators, have migrated 

 from the area and there is, therefore, little competi- 

 tion at a crucial time of development. 



A short spawning season, represented by a steep GSI 

 curve with a single peak, is a common strategy in 

 temperate marine zones. Black sea bass, butterfish, and 

 the searobins had the shortest spawning seasons, with 

 ripe fish present for only 3-5 months. These four 

 species are abundant during summer in the Middle 

 Atlantic (Wilk and Silverman 1976ab, Wilk et al. 1977, 

 Colvocoresses and Musick 1984), but not on the more 

 boreal Georges Bank (Overholtz and Tyler 1985). They 

 were collected at the highest average temperatures 

 during their reproductive peaks (Table 1). Most of the 

 other species described are abundant in both regions 

 and were collected in colder waters. 



Sherman et al. (1984) describe a ubiquitous or pro- 

 tracted spawning strategy for certain species including 

 silver hake and Urophycis spp., in which eggs are pro- 

 duced for several months and, although mortality is 

 high, some larvae survive when environmental condi- 

 tions and food supply are properly matched. In this 

 study, ripe female offshore silver and spotted hake, as 

 well as windowpane, summer, and winter flounder, 

 were collected for 5 or more months. Eggs and small 

 larvae of these species were observed for many more 

 months in other surveys (Clark et al. 1969; Smith et 

 al. 1975, 1980; Colton et al. 1979). 



Eggs are typically released from the ovaries of fishes 

 in batches (Bagenal 1978). In species with short repro- 

 ductive periods, these batches are released in the span 

 of a few days with all individual fish spawning at about 

 the same time. In multiple or serial spawners, batches 

 of eggs mature and are shed several times during a long 

 spawning season (Bagenal 1978, Burt et al. 1988). Ex- 

 amples of protracted spawners are silver hake which 

 produce as many as three batches of eggs per spawn- 

 ing season (Fahay 1974) and summer flounder which 



produce up to six batches (Morse 1981). Summer 

 flounder had the lowest mean GSI of any species col- 

 lected during this survey, apparently because their 

 eggs develop in batches and are released over an ex- 

 tended period. In contrast, the highest mean GSI noted 

 were for yellowtail and winter flounder which produce 

 only one batch of eggs per season (Howell 1983, Bur- 

 ton and Idler 1984). In both species, GSI increased 

 gradually in fall through winter as eggs matured, with 

 highest GSI levels being reached just prior to spring 

 spawning. Similarly, Burton and Idler (1984) reported 

 that GSI of winter flounder in Canadian waters grad- 

 ually rose during the 8 months before spawning takes 

 place in June. 



A high GSI does not always parallel a high level of 

 fecundity (Bagenal 1978). As an example, larger sum- 

 mer, yellowtail, and winter flounder have exhibited 

 fecundities of over 1 million (Bigelow and Schroeder 

 1953, Morse 1981, Lux and Livingstone 1982); egg 

 production in each of these species is accomplished, 

 however, on different timetables. 



Spotted hake and windowpane, both protracted 

 spawners, had bimodal GSI curves. Various sizes of 

 developing and ripe female spotted hake were collected 

 in fall, while a few large ripe females were collected 

 in spring. These findings may rellect behavioral dif- 

 ferences among size or age classes, or perhaps the 

 migratory habits of discrete unit stocks. Windowpane 

 exhibited two GSI peaks in the New York Bight dur- 

 ing 1974-75; however, continuous larval production 

 throughout the summer was noted in an earlier survey 

 of the area (Smith et al. 1975). Windowpane are perm- 

 anent residents in the Bight; that is, no evidence of 

 seasonal migration was found during this survey based 

 on observed changes in abundance, size structure, or 

 distribution of collections. Rather than a result of 

 emigration, the bimodal GSI curve exhibited by win- 

 dowpane may very well be a result of a reproductive 

 tactic in which spawning is curtailed during the year 

 if temperature rises above a preferred level. 



Some of the most important and prolific commercial 

 fisheries taking place in temperate seas around the 

 world are based on families of fishes, such as gadids 

 (codfishes and hakes) and pleuronectids (flounders), 

 that are typically very fecund and produce relatively 

 small pelagic eggs (Garrod and Horwood 1984). Of the 

 species described in this study, the pleuronectids, 

 yellowtail and winter flounder, and the bothid, sum- 

 mer flounder, have been reported to have extremely 

 high fecundities. Such species are well-suited for com- 

 mercial exploitation since they can recover rapidly from 

 natural or man-induced depletion. The gadids described 

 in this study are all small-bodied, mature early at a 

 relatively small size, and produce many tiny pelagic 

 eggs over a protracted spawning period; however, they 



