PEARCY and MYERS: LARVAL FISHES OF YAQUINA BAY 



the only common species with a distinct peak 

 of larval abundance in the summer (April- 

 September). Several species were collected 

 most months of the year: considering all years 

 together, larvae of Hyponiesus pretiosus were 

 found every month but May, June, July and 

 October, L. arniatus every month except 

 April-July, and Gobiidae type 1 every month 

 but April, May and July. 



Pacific Herring 



Catches of C. It. pallasi larvae during each 

 January-June period, 1960-1970, are illus- 

 trated for Buoy 21 in Figure 3. Herring larvae 

 were common from. Febi-uary-April, with peak 

 numbers usually in February and March. 

 Though sampling variability and the limited 

 number of samples precluded annual com- 

 parisons of abundance, no obvious long-term 

 trends, such as decreasing catches, are evident 

 during this 11-yr period, nor is there good 

 evidence for large fluctuations in larval num- 

 bers. This suggests a fairly stable population of 

 spawning herring over this time period. 



The initial occurrence of larval herring 

 varied among years, from January to March, 

 suggesting annual differences in time of spawn- 

 ing or hatching times (e.g., contrast 1969 and 

 1970 with 1961-1963). This variability may 

 be related to water temperature. The surface 

 temperature of first larval occurrence varied 

 from 7.3°C to 10.5°C (average = 9.0°C). To 

 estimate date of first spawning, incubation 

 time was calculated from a curve of incubation 

 times vs. temperature (Outram, 1955; Taylor, 

 1971; Steinfeld, 1972). Incubation was estimated 

 to range between 12 and 17 days for the first 

 herring larvae caught during these years using 

 surface water temperatures at Buoy 21. (Because 

 herring spawn in shallow water, often inter- 

 tidally [Steinfield. 1972; Taylor, 1971; Hard- 

 wick, 1973] , surface temperatures were used.) 

 Surface temperatures averaged for the date of 

 first herring larval occurrence and the previous 

 17 days (2-3 observations) were plotted against 

 time of first larval occurrence after January 1 

 (Figure 4). This revealed a surprising relation- 

 ship: Years of earliest occurrence of larvae (i.e., 

 1969 and 1970) had lowest water temperatures 

 (< 8°C) preceding first catches, and most years 

 of latest occurrence (i.e. 1961. 1963, 1965, 1966) 

 had highest temperatures (>9.2°C) during 



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2 - 



_.*_ 



A I S I I N I D 



Figure 2. — Average monthly catches offish eggs and larvae 

 in Clarke-Bumpus samples at Buoy 21. Each point rep- 

 resents a monthly average for fish eggs each year, 1960- 

 1968, and for fish larvae each year, 1969-1970. No samples 

 were available from April-July 1966. 



incubation of the first hatch. Thus, factors other 

 than water temperature appear to be important 

 in determining the time of the initial spawning 

 of herring in Yaquina Bay. 



Steinfeld (1972) observed from egg surveys 

 in Yaquina Bay that herring had four major 

 spawnings during February and March 1970. 

 These occurred at about 2-wk intervals starting 

 in early February, the most intensive spawnings 

 coinciding with highest tides. Newly hatched 

 larvae would therefore be expected in most of 

 the catches throughout the larval periods. 

 Measurements of larvae contributing to early 

 and late peaks in 1964 and 1967 showed that 

 recently hatched larvae (6-8 mm) were indeed 

 present in April, but as expected, the percentage 

 of small larvae was lower later in the year. 



HORIZONTAL VARIATIONS 



The average number of larvae collected at the 

 different stations in both the estuary and the 

 open ocean are listed in Table 4, permitting 

 comparison of horizontal variations of relative 

 abundance at nine stations from 8 miles up the 



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