LIFE HISTORY CHARACTERISTICS OF 

 PANDALUS MONTAGUI AND DICHELOPANDALUS LEPTOCERUS 



IN PENOBSCOT BAY, MAINE 



David K. Stevenson^ and Fran Pierce^ 



ABSTRACT 



A number of life history characteristics of two species of pandalid shrimp from Penobscot Bay, ME, were 

 inferred from length-frequency and relative abundance data collected on five occasions during a bottom 

 trawl survey in 1980-81. Pandalus montagui is a sequential hermaphrodite. Sex transition occurs 

 throughout the year, but most transitional individuals were observed in late March. Most individuals change 

 sex shortly before or after reaching age 2, but some do so either a year earlier or a year later. Ovigerous 

 females were observed from late November through January; eggs are apparently produced during the sec- 

 ond, third, and fourth years. Fifteen percent of the age-group caught in the fall of 1980 were females 

 which may never have functioned as males. Growth was rapid in the spring and summer and negligible in 

 the late fall and winter. Females which changed sex at age 1 were larger than females which changed sex a 

 year later. Dichelc/pandalus leptocerus is not hermaphroditic. Ovigerous females were collected primarily in 

 late November and early December. Some females produce eggs during their first and second years, but 

 most do so only during their second year. None of the females caught during this study appeared to be older 

 than age 2; a few large males remained in the population during their third year of life. Females of both 

 species were larger than males of the same age-group, a distinction which was attributed to differences in 

 growth rate and, for P. montagui, was associated with earlier sex transition. Larger shrimp of both species 

 migrated down the Bay into deeper water as the winter progressed. 



The Pandalidae are a family of boreal, subarctic 

 shrimp composed of 2 genera and about 20 species. 

 Four species {Pandalus borealis, P. montagui, P. 

 propinquus, and Dichelapandalus leptocerus) are 

 common in offshore waters of the Gulf of Maine 

 (Wigley 1960). Of these, P. borealis is the largest, 

 reaching a maximum total length of 17-18 cm (7 in), 

 and has been the object of a directed winter fishery 

 in coastal waters of the Gulf of Maine since the late 

 1930s (Scattergood 1952) and in coastal and offshore 

 waters since 1958^. This species is also exploited 

 commercially on the west coast of North America, in 

 the Canadian Maritime Provinces, on the west coast 

 of Greenland, in the Norwegian and North Seas, and 

 in the northwest Pacific (Balsiger 1981). 



Pandalus montagui and D. lefptocerus are smaller 

 species (maximum length 10 cm or 4 in), which are 

 harvested incidentally with P. borealis in the Gulf of 



'Zoology Department, University of Maine, Orono, ME 04469 

 and Maine Department of Marine Resources, West Boothbay Har- 

 bor, ME 04575. 



^Maine Department of Marine Resources, West Boothbay Har- 

 bor, ME 04575. 



^Stickney, A. P. 1980. A characterization of the northern 

 shrimp fishery of Maine. In C. J. Walton (editor). Fisheries 

 management and development. Vol. Ill, Element D: Character- 

 ization of the shellfisheries, p. 244-293. Completion report to the 

 State Planning Office, Oct. 1, 1978-Sept. 30, 1979, Maine Depart- 

 ment of Marine Resources, Augusta. 



Maine, but have little or no market value because of 

 their size. Pandalus montagui is also harvested as an 

 incidental species in the Gulf of St. Lawrence 

 (Balsiger 1981), and for many years was the object of 

 several localized commercial beam trawl fisheries in 

 the southern North Sea and in Morecambe Bay, 

 northwest England, until declining stock sizes led to 

 the demise of the fisheries in the Thames estuary 

 (described by Mistakidis 1957) and Morecambe Bay 

 in the 1950s and 1960s. Warren (1973) described a 

 fishery for P. montagui in the Wash on the east coast 

 of England which was still active in the early 1970s. 

 Pandalus propinquus is also smaller than P. borealis 

 and is generally restricted to deeper water (165-330 

 m in New England waters according to Wigley 

 1960); consequently it is rarely taken in Gulf of 

 Maine commercial catches. 



Pandalus montagui is differentiated taxonomically 

 into two subspecies: P. montagui tridens in the 

 North Pacific and P. montagui montagui in the 

 North Atlantic from the Arctic south to the British 

 Isles and Cape Cod (Simpson et al. 1970) or Rhode 

 Island (Rathbun 1929). According to Simpson et al. 

 P. montagui montagui is found in estuaries, coastal 

 waters, and offshore in depths of 5 to over 700 m, 

 but is more common in shallow waters (20-90 m); at 

 depths > 90 m it is gradually replaced by P. borealis. 



Manuscript accepted August 1984. 



FISHERY BULLETIN: VOL. 83, NO. 3, 1985. 



219'^^ 



