THE BIOLOGY OF PSEUDOCALANUS MINUTUS IN THE GULF OE MAINE AND BAY OF FUNDY CHARLES J. FISH (From the Woods Hole Oceanographic Institution' 1 ) INTRODUCTION The present paper forms the second of a series on the biology of zooplankton species in the Gulf of Maine and Bay of Fundy, with spe-cial reference to production and dispersal. As in the case of Calanus finmarchicus (Fish, 1936) there have been two objectives; first, a de-termination of breeding seasons, annual number of broods, and rate of growth; second, an evaluation of different spawning areas and dis-persal of eggs and larvae. For a description of the area covered, loca-tion of stations and methods, the reader is referred to the aforemen-tioned report. The studies were carried on between July 28, 1931 and September 29, 1932 for the International Passamaquoddy Fisheries Commission. REGIONAL DISTRIBUTION OF THE ADULT STOCK 2 Pseudocalanus ininutus was found by Bigelow (1926, pp. 276-277) to be nearly as universal as Calanus in the Gulf of Maine, distributed in-differently in the coastal zone, the deeper parts of the basin, and on off-shore banks. It was somewhat more nearly universal close along shore but the numbers actually present averaged larger in the basin, entrant channels, and along the offshore slope. In 1931 and 1932 it was found generally distributed in both neritic and offshore waters. Being more indifferent to neritic environmental factors than Calanus and with an apparently somewhat greater thermal range, Pscudocalanus occurs to some extent throughout the year in inshore waters north of Cape Cod. However, like other boreal arctic species, its numbers de-cline rapidly with rising summer temperatures in shallow areas, and off-shore Bigelow (Ibid., p. 277) observed that there is a general tendency to leave the uppermost stratum in April and May. In Passamaquoddy Bay in 1932 there was a decline in the relative percentage of Pscudocalanus from 84.7 per cent on June 20 to 2.8 per cent on July 30, with a corresponding reduction in the volume of plank-ton from 26.7 cc. to 1.9 cc. Later it rose again to 12.1 per cent ac-1 Contribution No. 94. " Adult stock " includes late copepodites (for the most part stage V) appear-ing in the coarse net hauls. 193
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