FISHERY BULLETIN: VOL. 76. NO 4 



fatal. The authors suggested, but did not dem- 

 onstrate, an environmental contaminant etiology, 

 possibly associated with bottom detritus. Other 

 bivalve molluscs in Chesapeake Bay contain neo- 

 plasms. American oysters, Crassostrea uirginica, 

 were found with hematopoietic neoplasms (Farley 

 1969a; Couch 1969, Frierman 1976), and indi- 

 vidual oysters have been reported to contain other 

 types of neoplasms (Pauley 1969; Couch 1970). 



Much of the evidence associating certain neo- 

 plasms offish and shellfish with pollutants should 

 be considered as circumstantial but provocative 

 (Rentchnick 1976). Many of the neoplasms have 

 been reported from bottom-feeding fish and de- 

 tritus or filter-feeding bivalves, as was pointed out 

 by Harshbarger.^ Chemical carcinogens such as 

 certain heavy metals and hydrocarbons can be 

 concentrated in surficial layers of bottom sedi- 

 ments and can thus be readily available to ani- 

 mals inhabiting that zone. It should be noted, 

 though, that a number of recent studies of neo- 

 plasms in fish and shellfish have found no obvious 

 relationship between neoplasms and specific en- 

 vironmental factors. 



Skeletal Anomalies 



Skeletal anomalies, particularly those of the 

 spinal column, are commonly observed in fish and 

 are the subject of an extensive literature (see Rick- 

 ey 1972, for a recent summary and Dawson 1964, 

 1966, 1971, and Dawson and Heal 1976 for a com- 

 plete bibliography). 



Such anomalies may be genetic, resulting from 

 mutations or recombinations; epigenetic, acquired 

 during embryonic development; or postembryonic, 

 acquired during larval development, at metamor- 

 phosis, or during juvenile development (Hickey 

 1972). Spinal flexures and compressions, as well as 

 vertebral fusions, have been observed in many 

 teleost species, as have head and fin abnor- 

 malities. Evidence exists for a hereditary basis for 

 some skeletal anomalies (Gordon 1954; Rosenthal 

 and Rosenthal 1950), but other evidence points to 

 effects of environmental factors such as tempera- 

 ture, salinity, dissolved oxygen, radiation, dietary 

 deficiencies, and toxic chemicals. For example, in- 

 creased percentages of abnormal embryos and lar- 

 vae of Atlantic herring, Clupea harengus, resulted 



'Harshbarger, J.C. 1974. Activities report (of the) registry 

 of tumors in lower animals 1965-1973. Smithson. Inst., Wash., 

 D.C., 141 p. 



from experimental exposures to sulfuric acid 

 waste water (Kinne and Rosenthal 1967) and to 

 the algicides 2,4- and 2,5 dinitrophenol ( Rosenthal 

 and Stelzer 1970). 



Recently, increased prevalences of skeletal de- 

 formities and anomalies, considered to be 

 pollution-associated, have been recognized in a 

 few fish species from southern California, the 

 British Isles, and Japan. In studies carried out in 

 California, skeletal deformities occurred with 

 greater frequency in samples from areas with sig- 

 nificant pollutant stress (Valentine and Bridges 

 1969; Valentine et al. 1973). Exposure of fry to 

 very low concentrations of DDT ( <1 ppb) produced 

 anomalies in fin rays (Valentine and Soule 1973). 



Probably the most convincing observational 

 evidence for environmental influences on induc- 

 tion of skeletal abnormalities in marine fish is 

 that presented by Valentine (1975). Examining 

 samples of barred sand hass, Paralabrax nebulifer, 

 Valentine found significantly higher prevalences 

 of anomalies, particularly gill raker deformities, 

 in fish from the southern California coast (Los 

 Angeles and San Diego) than from the Baja 

 California coast. The anomalies increased in fre- 

 quency and severity with increasing size of the fish 

 and an association with disturbed calcium 

 metabolism was suggested. The author pointed to 

 the high chlorinated hydrocarbon and heavy 

 metal levels which characterize the California 

 coastal area (Schmidt et al. 1971; Galloway 1972), 

 but emphasized that a causal relationship with 

 increased prevalence of anomalies had not been 

 established. However, Valentine's suggestion of a 

 possible causal relationship between high en- 

 vironmental levels of chlorinated hydrocarbons 

 and heavy metals, both of which are known to 

 interfere with calcium metabolism, and skeletal 

 anomalies in fish seems reasonable, in view of 

 experimental evidence from a wide range of ver- 

 tebrates (Ferm and Carpenter 1967; Lehner and 

 Egbert 1969; Peakall and Lincer 1970; Pichirallo 

 1971; McCaull 1971; Galloway 1972). 



Valentine (1975) referred briefly to additional 

 observations on two other Pacific coastal 

 species — California grunion, Leuresthes tenuis, 

 and barred surfperch, Amphistkhus argenteus — 

 in which gill raker anomalies increased in fre- 

 quency with age, and were "virtually restricted to 

 [samples from] fishes from Southern California." 

 This finding in three species reduces the likelihood 

 that frequency differences could be attributable to 



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