made to determine the seasonal and areal 

 distribution of the larval fishes. 



METHODS 



Humboldt Bay is located on the north 

 coast of California (Fig. 1). It is 14 miles 

 long, shallow with extensive mudflats, and is 

 mostly bordered by marshlands and sandy 

 beaches. Areata and South Bays are uniform- 

 ly shallow and unnavigable outside the narrow 

 channels, except at high tide. Limited fresh- 

 water entry is provided by one small river, 

 three creeks, and minor tributaries. 



Five sampling stations, each 153 m (500 ft) 

 long, were selected (Fig. 1). Stations 1 and 

 4 were similar in depth (5-8 m) and were lo- 

 cated in major drainage channels adjoining 

 expansive eelgrass mudflats. Station 2, ad- 

 jacent to a rock jetty, experienced the strong- 

 est tidal currents and was the deepest station 

 (12-15 m). Station 3 was relatively shallow 



(3-5 m) and bordered by a gently sloping 

 sandy beach. Station 5 was the shallowest 

 (2-3 m) and experienced the greatest varia- 

 tion in salinity and temperature. 



An attempt was made to sample the entire 

 water column at each station, making alter- 

 nate bottom and oblique tows at biweekly 

 intervals. A 1-m plankton net of No. mesh 

 (aperture size 0.57 mm) was used with a 

 centrally located flowmeter. For bottom 

 samples, a macroplankton sled (Fig. 2) was 

 towed at 1-3 knots. The sampling gear was 

 retrieved, using a variable-speed winch ap- 

 paratus powered by a 4-hp engine with a 

 4-speed automobile transmission. 



Larval and juvenile fishes were collected 

 in 118 tows over a 12-month period. All samples 

 were fixed and held in 5% formaldehyde in sea- 

 water. Fishes were sorted, identified, enumer- 

 ated, and measured, using an ocular microm- 

 eter mounted in a stereozoom dissecting micro- 

 scope. Identifications were made with the assist- 

 ance of E. H. Ahlstrom (personal communica- 

 tion) and by using several keys and descriptions, 

 the most useful of which were: Ahlstrom 

 (1965), Bolin (1944), Breder and Rosen (1966), 

 Budd (1944), Clothier (1950), Hart and 

 McHugh (1944), Hickman (1959), Jones (1962), 

 Orcutt (1950), and Orsi (1965). 



Surface and bottom temperatures and 

 salinities were taken with each sampling. 

 Temperatures were recorded using a standard 

 nonreversing mercury thermometer while 

 salinities were determined with an induc- 

 tion salinometer in the laboratory. 



RESULTS 



Environment 



Figure 1. — Humboldt Bay, Calif., and the five sampling 

 stations. 



In general, vertical similarities in temper- 

 ature and salinity reflect the extent of mixing 

 and low freshwater inflow into the Bay (Fig. 3 

 and 4). Water temperatures from January to 

 December 1969, ranged from 7.5° to 19.6°C 

 (Fig. 3). The temperature began to increase 

 in February and reached a maximum in late 

 May, remaining high until September. 

 Stations 1, 2, and 3 exhibited the lowest over- 

 all combined surface and bottom temperature 

 means (11.4°, 11.0°, and 11.3°C, respectively), 

 while stations 4 and 5 had relatively high 



