This report describes the experiments conducted by research groups located at the St. Andrews Biological Station, Gulf Fisheries Centre, Bedford Institute of Oceanography; and Queen's University. Environmental conditions, such as water temperature and salinity, may affect the toxicity of chemically and mechanically dispersed crude oil when accidental spills occur. Impacts of oil spills on local fish populations will also vary depending on the relative sensitivities of resident species and stocks.
The objectives of the herring studies conducted by the Gulf Fisheries Centre were to:
- determine the influence of rearing temperatures (7, 10 and 15C) and salinities (7.5, 15 and 30) on the toxicity of Arabian Light (ALC) to Atlantic herring (Clupea harengus)embryos;
- determine if different species (Atlantic vs. Pacific herring [Clupea pallasii]) and spawning stocks (spring vs. fall spawning Atlantic, British Columbia vs. Alaska Pacific) of herring embryos respond similarly to chemically and mechanically dispersed crude oils; and
- compare the toxicity of three crude oils (ALC; Alaska North Slope, ANS; Mediterranean South American, MESA).
Toxicity was assessed from survival-to-hatch, length-at-hatch and the prevalence and severity of developmental abnormalities, incorporated into the blue sac disease severity index (BSD SI), in herring exposed throughout the embryo stage.
All end-points assessed indicated greater toxicity of ALC when Atlantic fall embryos were reared at 7C compared to 10 or 15C. This increased toxicity at a low rearing temperature did not appear to result from dispersant effectiveness or PAH solubility as expected but to cold stress, increased exposure duration or reduced metabolic processes. Lower salinities (7.5 and 15) seemed to increase ALC toxicity by increasing PAH concentrations in these rearing salinities, likely resulting from higher PAH solubility. Atlantic herring were found to be more sensitive than Pacific herring. Within species, sensitivity differences were detected between stocks of Pacific herring, with herring from Alaska being more sensitive than herring from British Columbia.
See also: Appendices A-H