CROSS: FIN EROSION AMONG FISHES 



Table l. — Taxonomic list of fish affected with fin erosion collected in 622 otter trawls on the Palos Verdes shelf 



from 1971 through 1982. 



seasonalized data were determined by linear re- 

 gression. 



The effects of fin erosion on the population of 

 Dover sole on the Palos Verdes shelf were 

 examined using the original data of Mearns and 

 Harris (1975)^ that consisted of length, weight, 

 sex, and age (from otoliths) of 328 Dover sole col- 

 lected in 1972 and 1973. 



Size-frequency distributions between Dover sole 

 of the same age with and without fin erosion were 

 compared with a Kolmogorov-Smirnov two sample 

 test (Siegel 1957). A one-tailed test was used be- 

 cause the disease might be expected to reduce the 

 growth rate of affected individuals. 



Weight-length relationships among male and 

 female Dover sole with and without fin erosion 

 were compared with the geometric mean regres- 

 sion 



log w = log a + b (log /) 



where w = weight, I = length, and a and b are 

 fitted constants (Ricker 1973). The regression co- 



Mearns, A. J., and L. Harris. 1975. Age, length, and 

 weight relationships in southern California populations of Dover 

 sole. Tech. Memo. 219, 17 p. Southern California Coastal 

 Water Research Project, Long Beach. 



efficients were compared statistically using the 

 method of Clarke (1980). 



The survival rate of Dover sole with and without 

 fin erosion was compared. Using an age-length key 

 developed from the data, ages were assigned to all 

 Dover sole captured in LACSD monitoring trawls 

 on the Palos Verdes shelf from 1972 through 1975. 

 Survival rate (S) was calculated from age t (in 

 years) to age ^ -I- 1 from 



S = 



N 



t + i 



N. 



where A^ = the number caught (Ricker 1975). Sur- 

 vival rates of fish with and without the disease 

 were compared with a ^-test after the data were 

 transformed to the reciprocal (l/x) to stabilize the 

 variance. A one-tailed test was used because the 

 disease might be expected to reduce the survival 

 rate of affected individuals. 



RESULTS 



From 1971 through 1982, LACSD made 622 

 monitoring trawls on the Palos Verdes shelf. Fin 

 erosion was reported for 15,680 individuals (9.2% 

 of all individuals collected) representing 29 

 species (23.8% of all species collected) (Table 1). 



197 



