Appendix 3. Species life history notes 



The five "typical" life stages considered by the ELMR 

 program were adults (A), spawning adults (S), juve- 

 niles (J), larvae (L), and eggs (E). Adultswere defined 

 as reproductively mature individuals, Juveniles as 

 immature but otherwise similar to adults, Spawning 

 adults as those releasing eggs and sperm, Larvae as 

 the early developmental stage(s) from hatching to a 

 form resembling the adult, and Eggs as the early 

 developmental stage from spawning to hatching. The 

 complex life histories of some species, and the subse- 

 quent difficulty in placing them into a comprehensive 

 classification scheme, necessitatethe following supple- 

 mentary information when there was deviation from 

 the typical categorization (e.g., ovoviviparous repro- 

 duction in spiny dogfish). 



Invertebrates. Sessile invertebrates, such as bivalves, 

 usually have a patchy rather than a uniform distribu- 

 tion. Specific areas may contain acceptable salinity 

 regimes, but suitable bottom habitat for colonization 

 may not exist. Therefore, the total areal distribution of 

 these organisms may have been overestimated; none- 

 theless, inhabited zones are identified. Specific habitat 

 requirements and life history characteristics of a num- 

 ber of invertebrate species are provided below. 



• Blue mussel: Mytilus edulis is common on hard 

 substrates in intertidal and subtidal beds throughout 

 the Gulf of Maine. The reproductive cycle may vary 

 significantly between years, and larvae may settle out 

 at low levels throughout the year in certain areas. High 

 winter mortality occurs in some years and locations 

 (Newell 1989). 



• Sea scallop: Placopecten magellanicus is not regu- 

 larly found in < 20 ppt and beds in estuarine areas tend 

 to be patchy, especially compared to those further 

 offshore (Mullen and Moring 1986, Shumway 1991). 

 Eggs are buoyant and larvae remain pelagic for 4-6 

 weeks before settling to the bottom. Spawning is 

 intermittent and a percentage may mature in one year 

 in some areas. 



• American oyster: Crassostrea virginica is also 

 known as the Eastern oyster. It is present only in 

 relatively warm subtidal or intertidal areas of a few 

 estuaries in the study area. Northern Atlantic oysters 

 may be a distinct physiological race with spawning 

 temperature requirements (Sellers and Stanley 1984) 

 different from those of Mid-Atlantic oysters. (Ostrea 

 edulis, the European oyster, was not assessed in this 

 study but it has been introduced to some areas of the 

 Maine coast through mariculture projects.) 



• Northern quahog: Mercenaria mercenaria is also 

 known as the hard clam. Populations north of Massa- 

 chusetts are small and patchy in relatively warm, high 

 salinity (>20 ppt) areas. In the extreme northern popu- 

 lations, spawning success may be limited (Stanley and 

 DeWitt 1984). 



• Softshell clam: Mya arenaria usually spawns once 

 a year in the northern Gulf of Maine, whereas southern 

 populations have exhibited bimodal spawning. Settle- 

 ment of seed clams tends to be very patchy and 

 dependent upon hydrographic conditions and/or pre- 

 dation (Newell and Hidu 1986). Mortality of eggs, 

 larvae, and seed clams is extremely high. Larvae are 

 less tolerant of low salinities than adults. Its northern 

 range is limited by water temperature that must be >1 2- 

 15°C for successful spawning. In some areas (e.g., 

 Machias Bay) artificial seeding programs may tempo- 

 rarily increase the abundance of juveniles. 



• Daggerblade grass shrimp: Palaemonetes pugio\s 

 also known as the grass shrimp. It is most abundant 

 locally in vegetated habitats of warm bays. Soon after 

 mating, females fertilize and extrude eggs onto their 

 pleopods where they are held for up to two months until 

 hatching as larvae (Williams 1 984). This species may 

 be confused or grouped with P. vulgaris, which is more 

 boreal and prefers higher salinities than P. pugio. P. 

 pugio is much more common south of Cape Cod. 

 Juveniles mature early in their first year. For the pur- 

 poses of the ELMR program, the spawning stage (S) is 

 defined as the period of mating/fertilization/egg extru- 

 sion; the larval stage (L) consists of the protozoeal and 

 zoeal stages; and the egg stage (E) refers to ovigerous 

 females. 



• Northern shrimp: Pandalus borealis is the most 

 common species of its genus in the Gulf of Maine, but 

 the closely related P. propinquus and P. montagui are 

 also found in some areas. This species is hermaphro- 

 ditic, maturing first as males to spawn in the summer at 

 approximately 2.5 years, then passing through a series 

 of transitional stages to spawn the next summer as 

 females at 3.5 yr. Soon after mating in the summer/ 

 early fall, females fertilize and extrude eggs onto their 

 pleopods, where they are held for several months until 

 hatching as larvae the following spring (Haynes and 

 Wigley 1969, Shumway et al. 1985). The bulk of the 

 inshore fishery consists of berried females that have 

 moved inshore in the fall and winter to release their 

 larvae. The distribution of juveniles is largely unknown. 

 For the purposes of the ELMR program, the spawning 

 stage (S) is defined as the period of mating/fertilization/ 

 egg extrusion; the larval stage (L) consists of the 

 protozoeal and zoeal stages; and the egg stage (E) is 

 synonymous with ovigerous females. 



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