Effect of Suspended Iron Hydroxide on the Hatchability and Embryonic Development of the Coho Salmon

Coho salmon (Oncorhynchus kisutch) eggs were fertilized and fry were incubated at 10°C in the presence and absence of suspended iron. Suspended ferric hydroxide at a concentration of 3 ppm had no apparent effect on the hatchability, embryonic development, or survival and maturation of newly hatched coho salmon still attached to the yolk mass (alevins). OHIO J. SCI. 78(1): 34, 1978 The deposition of suspended solids on aquatic substrates may result in reduced hatched alevins from spawning areas (Campbell 1954, Cooper 1956). A major source of these suspended materials is the discharge of ferric hydroxide (Fe(OH)3) into streams which has become a major source of pollution throughout the northeastern United States. Ferric hydroxide may be derived from wells and natural springs where iron salts occur in rock strata or from acid mine drainage as a result of the oxidation of iron pyrite (FeS2). As pH increases, dissolved iron salts will hydrolyze to ferric hydroxide and precipitate as a yellowbrown slime on the bottom of streams. This precipitate has been shown to cause a variety of physiological changes (Brenner et al 1977), including acute respiratory distress in fish (Larson and Olsen 1950), or affect the development, survival, growth, and reproduction of invertebrates and fish on a long-term basis (Sykora 1970, Sykora et al 1972a, Sykora et al 1972b, Sykora et al 1975, Smith et al 1973, Smith and Sykora 1976). The effect of iron hydroxide on the embryonic development of the coho salmon {Oncorhynchus kisutch) was investigated using facilities at the Pennsylvania Fish Commission's fish culture station in Tionesta, PA. '•Manuscript received October 4, 1976 and in revised form July 8, 1977 (#76-78). METHODS AND MATERIALS Coho salmon eggs were received from the Pennsylvania Fish Commission's Walnut Creek station, Erie, PA, by the Tionesta station on 8 and 11 November 1973. Eggs were collected and fertilized at the Walnut Creek Station and transported by the Pennsylvania Fish Commission to the Tionesta station, and the time interval between fertilization and beginning of incubation at 10°C was less than 24 hrs in all cases. The different development stages (as denned by Zeitoun and Tack, 1974 and Brenner et al, 1976) were identified by removing 10 eggs from the hatching jars at 5-day intervals until the eye-up stage, with 5 being placed in Kahl's fixative and 5 frozen at — 20°C. Frozen eggs were analyzed for total iron by atomic absorption spectrometry. Fixed specimens were dehydrated in alcohol and xylol and prepared as whole mounts on transverse sections. Toluene was used as a clearing agent before infiltration of the embryo (Guyer 1936). Embryos were embedded in Tissuemat (Fisher) at 52.5==0.5, sectioned at 8 /x, stained with hematoxylin counter stained with eosin and mounted in Canada balsam. Whole mount embryos, after removal of the told sac, were stained with alum cochineal solution. The hatchability of eggs was determined by the removal and counting of dead eggs daily during incubation. Dead alevins were also removed from the rearing tanks and recorded daily until 90 days of age. After 90 days, alevins from both groups were mixed in rearing ponds and further observations on survival were not continued. Only eggs received from AValnut Creek Station were used in the embryonic development study to assure that all test specimens were obtained from a common source. Ova from Michigan (Dept. of Environmental Resources) were observed only for hatchability and alevins mortality. Upon arrival at Tionesta Station,