species are commonly found in nearshore 

 areas. 



Four fish species (Cynoscion nobilis, Steno- 

 brachius leucopsarus, Tarltonbeania crenu- 

 laris, and Cyclothone acclinidens) were not 

 previously known to exist in the Bay and 

 represent new introductions to the list of Bay 

 fauna (Gotshall and Allen, in preparation). 1 

 The latter three species are classified as meso- 

 pelagic fishes and exhibit diel migration in 

 offshore waters (Pearcy and Laurs, 1966). 

 Cyclothone acclinidens is recorded as abun- 

 dant and is commonly found at a depth of 

 100 ft or more (Fitch and Lavenburg, 1968). 

 The occurrence of these fishes in shallow in- 

 shore areas is most likely due to fortuitous 

 drifting of larvae into Humboldt Bay. Fast 

 (1960) believed seasonal oceanographic con- 

 ditions involving changes in current directions 

 were responsible for large catches of Steno- 

 brachius leucopsarus in Monterey Bay. Like- 

 wise, for Humboldt Bay, onshore currents 

 resulting from southerly winds combined with 

 tidal movements could bring these mesopelagic 

 larvae into the Bay. Wind direction data from 

 near the Bay for the periods of capture of 

 these fishes generally indicate either mixed 

 conditions or predominate southerly winds. 

 It has also been noted (Ahlstrom, 1959) that 

 most fish larvae, including the three meso- 

 pelagic species in this survey, were found in 

 the upper part of the thermocline to ap- 

 proximately 125 m. This would place the fish 

 larvae in the waters most influenced by sur- 

 face winds. A concluding factor is that all but 

 two of the specimens representing four 

 species were captured near the Bay entrance. 



Localization in distribution was evidenced 

 with the bothids, pleuronectids, and offshore 

 species near the Bay entrance, and cottids 

 and gobies in Areata Bay. Their limited dis- 

 tribution were most likely due to being spawn- 

 ed and surviving in large numbers only within 

 certain areas. For many species the small 

 numbers captured obviate a discussion of 

 their distribution. 



Winter freshwater runoff and shallow depth 

 were responsible for the wide range in salinity 

 and temperature in station 5. Concurrently, 



1 Gotshall, D., and G. H. Allen. Annotated checklist 

 of Humboldt Bay. Manuscript in preparation. 



the number of species found at station 5 was 

 the lowest which may reflect the limiting en- 

 vironmental conditions. The estuarine waters 

 at the other four stations were mixed well 

 from surface to bottom by virtue of the large 

 tidal prism relative to the volume of the Bay 

 and the turbulence on both the flood and ebb 

 tide stages. 



In the pelagic larval fish surveys along the 

 California coast, most notably the California 

 Cooperative Fisheries Investigations, larval 

 fish abundance is measured in numbers of 

 individuals below 1 square meter of sea sur- 

 face. This analysis is confined to results of 

 oblique plankton net hauls. For surveys in 

 estuarine areas, this method becomes more 

 complicated because of the shallowness of 

 the stations which often necessitates develop- 

 ment of specialized sampling gear as in this 

 study. In order to compare the results of 

 the sled and the oblique tows, we chose to 

 use larvae per cubic meter strained. This and 

 similar values have been commonly used in 

 studies along the east coast of the United 

 States (Lewis and Mann, 1971; Pearcy and 

 Richards, 1962; Richards, 1959). It should 

 be noted, however, that numbers of fish larvae 

 per volume of water strained are not strictly 

 comparable values but density measurements. 

 If the total number of larvae in an area are 

 used for the analysis of horizontal distribu- 

 tion, more meaningful conclusions of the rela- 

 tive productivity of different areas can be 

 formed. 



The Pacific coast of the United States (ex- 

 cluding Alaska) has remarkably few estu- 

 aries. Consequently, those that do exist are 

 focal points for population concentrations 

 and commercial and industrial developments. 

 The extent to which these marine environ- 

 ments have been modified by man's activities 

 is not fully known. Yet the rate of activity 

 is increasing and the need to understand and 

 evaluate the effects of these activities on the 

 ecosystem has become important. Estuarine 

 larval fish surveys can provide information 

 relating to the utilization of inshore areas 

 for spawning and nursery grounds both in 

 space and time. By monitoring the larval 

 fish population over long periods of time, it 

 is also possible to determine the rate and 

 extent of change in the abundance and species 



