Survival and growth over an environmental range of temperature and salinities were examined in order to help assess the importance of these environmental factors in affecting the distribution, abundance and survival of larvae and provide greater understanding of factors affecting fluctuations in adult Pandalus jordani Rathbun population sizes. Larvae were shown to have a wide tolerance to salinity, especially in the early stages, but a relatively narrow tolerance to temperature. The optimal temperatures for survival, 8 ~ to 11~
were also optimal for growth as reflected by maximal growth increments and body size. It is therefore felt that fluctuations in temperature as seen within and between successive larval seasons would have profound effects on larval survival, growth rates and size at metamorphosis to the benthic juvenile phase.
Introdu~ion
Attempts have been made to correlate incoming year-class strength and envi-Shrimps of the family Pandalidae support ronmental conditions in a number of important fisheries throughout the world, fisheries (for review see Gulland, 1965). Those of major importance are concentrated in cool temperate and boreal waters (Scrivner and Butler, 1971). Pandalus jordani Rathbun ranges from Unalaska (53 ~ 45'N; 166 ~ 40'W) to San Diego, California (32 ~ 30'N; 117~ at depths of 64 to 326 m (Rathbun, 1902). The population appears to have its maximum density off the central Oregon coast, but the species is also abundant in waters from northern California to at least Cape Beale, Vancouver Island (Dahlstrom, 1970). The highest catch rates occur off the Oregon and Washington coasts at depths of 110 to 183 m (Ronholt, 1963). Dahlstrom (1970) has compiled a broad synopsis of biological information on p. jordani based largely on data from California populations. Eight-fold fluctuations in landings associated with varying year-class strengths have been observed in this pandalid fishery during the 17 years from 1956 to 1973 (Lall, 1970;McCrary, 1973). These efforts were largely unsuccessful because little was known about the direct effects of environmental factors on larvae. Large errors also resulted from measuring larval mortality indirectly by back-calculating from the size of yearclasses after they were recruited to the fishery. The purpose of this study was to determine the survival and growth rates of Pandalus jordani larvae in relation to the temperatures and salinities they encounter during their lengthy pelagic development off the Oregon coast. These experiments, combined with field sampling, would help assess the importance of these environmental factors in affecting the distribution, abundance and survival of larvae and provide greater understanding of factors affecting fluctuations in the p. jordani fishery off Oregon. The results of the field sampling program will be reported separately.