Reproductive habits data and general life history information are still 

 lacking for a number of common marine and freshwater fishes. This is 

 especially true for fishes that presently have little commercial or sport 

 value. 



Stock assessment is of paramount importance in fishery management. Stock 

 assessment technology has developed rapidly over the past few years; however, 

 adequate data are lacking for many species (Brown 1976). The relationship 

 between stock size and recruitment remains poorly defined for many species. 

 More laboratory and field research is needed to understand the mechanisms of 

 fish reproduction and how environmental factors influence the survival of 

 fishes from egg to adult stages. 



Data are needed on the trends and significance of environmental contaminant 

 (pesticides, PCBs , and heavy metals) levels in fishes in the different 

 drainages and rivers. 



CASE STUDY: SHORTNOSE STURGEON 



The shortnose sturgeon, Acipenser brevirostrum , is the smallest in the family 

 of some 20 forms recognized worldwide and is a Federally listed endangered 

 species. It is a moderate-sized (to 42 inches or 107 cm), slow-growing, long- 

 lived (to 35 years or so) , anodromous fish. According to Bigelow and 

 Schroeder (1953), the shortnose sturgeon is scarce in the Gulf of Maine and 

 there is no reason to think it has ever been more plentiful there. 



Range and Distribution 



The shortnose sturgeon ranges historically from New Brunswick, Canada, to 

 Florida, typically in large tidal rivers such as the Potomac, Delaware, 

 Hudson, Connecticut, and St. John. In Maine, shortnose sturgeon occur in the 

 Sheepscot River (Fried and McCleave 1973), the Kennebec River, and the 

 Penobscot River systems (personal communication from T. Squires, Maine 

 Department of Marine Resources, Hallowell, ME; December, 1979). Information 

 is scarce but there is evidence that shortnose sturgeon enter the sea and 

 wander some distance from their parent stream (Bigelow and Schroeder 1953). 

 It is not so strongly migratory as other species. 



Reproduction and Growth 



Very little is known about the spawning and early life history of the 

 shortnose sturgeon; the young rarely are seen. Male shortnose begin to spawn 

 at a total length of about 51 cm (20 inches) and females at 61 cm (24 inches). 

 Reproduction occurs once every 3 years for individual females (Dadswell 1975). 

 Spawning apparently occurs in the middle reaches of large tidal rivers from 

 April to June, depending on location; adults apparently return to a parent 

 stream (Scott and Crossman 1973). In the Connecticut River, eggs have been 

 collected in late May near the river bottom when water temperature ranged 

 between 15° C and 17.8°C or 59°F to 64°F (Clayton et al. 1976). Bean (1903) 

 reported shortnose sturgeon spawning in the Delaware River in brackish or 

 nearly fresh water in depths of 2m to 9 m (7 feet to 30 feet). 



According to Scott and Crossman (1973), the eggs are dark brown, small, and 

 less numerous per pound of fish than in other sturgeons. The eggs of a 



11-48 



