FISHERY BULLETIN: VOL. 83, NO. 2 



20 60 100 140 180 220 260 300 



BSL (MM) 



FIGURE 3. — Size distributions of Dover sole, Microstomas 

 pacificus, with fin erosion (dashed line) and without fin erosion 

 (solid line) by 20 mm size class (i.e., 20-39 mm, 40-59 mm, ..., 

 300-319 mm) for all collections (1971-82) combined. The number 

 of individuals is presented to the right. BSL = board standard 

 length. 



sion was observed in 0.3% of the fish between 40 

 and 59 mm BSL, 3.8% of the fish between 60 and 79 

 mm BSL, and 17.7% of the fish between 80 and 99 

 mm BSL. The incidence of fin erosion peaked in 

 fish 120-139 mm BSL at stations close to the out- 

 falls, and in fish 140-179 mm BSL at more distant 

 stations. The proportion of fish with fin erosion in 

 a particular size class was greatest at stations 

 close to the outfalls and declined progressively 

 with increasing distance (Fig. 4). 



Seasonal Trends 



Time series analyses of the quarterly trawl data 

 (1979-82) for Dover sole at T4 and T5 showed con- 

 sistent seasonal peaks in the total catch and in the 

 number of individuals with fin erosion, but not in 

 the proportion of individuals with the disease (Fig. 



20 60 100 140 180 220 260 300 



BSL (mm) 



FIGURE 4. — Percent of Dover sole, Microstomus pacificus, with 

 fin erosion in each 20 mm size class (i.e., 20-39 mm, 40-59 mm, 

 . . . , 280-299 mm) at 61 m and 137 m on the sampling transects. 

 Data for each station are 12-yr totals. BSL = board standard 

 length. 



5). The seasonal indices of total catch and number 

 with fin erosion were highest in the second 

 (April-June) and third (July-September) quarters 

 at 61 m and in the third and fourth quarters at 137 

 m. The magnitude of the seasonal swing was 

 greater at 61 m. 



Examination of the deseasonalized data re- 

 vealed that there was no change in the total catch 

 of Dover sole, the number of individuals with fin 

 erosion, or the proportion of individuals with fin 

 erosion at 61 m between 1979 and 1982 (Table 7). 

 At 137 m, there was a significant decline in the 

 number of Dover sole with fin erosion at T4 and T5, 

 and a significant decline in the total catch and 

 proportion of individuals with fin erosion at T4 

 (Table 7). 



Size at Age 



The Mearns and Harris (footnote 3) data were 

 examined for differences in the size-frequency dis- 

 tributions between Dover sole with and without 

 fin erosion at a particular age. There were no signi- 

 ficant differences for fish age 2 (x^ = 0, df = 2, 

 P > 0.90), age 3 (x^ = 1.27, df = 2, 0.50 <P < 

 0.70), age 4 (x^ = 1-71, df = 2, 0.30 < P < 0.50), 

 or age 5 (x^ = 2.12, df = 2, 0.30 <P < 0.50). 



200 



