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API 4412

1985 Edition, 1985

Complete Document

Oil Effects on Spawning Behavior and Reproduction in Pacific Herring (Clupea Harengus Pallasi)



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Product Details:

  • Revision: 1985 Edition, 1985
  • Published Date: October 1985
  • Status: Not Active, See comments below
  • Document Language: English
  • Published By: American Petroleum Institute (API)
  • Page Count: 134
  • ANSI Approved: No
  • DoD Adopted: No

Description / Abstract:

EXECUTIVE SUMMARY

Because herring spawn in shallow coastal waters, there is concern that these commercially valuable fish or their deposited eggs might be impacted by oil spills. Potential effects of crude oil on the reproductive success of Pacific herring, Clupea harengus pallasi, were studied with laboratory experiments during the 1982 and 1983 spawning seasons. Preliminary experiments in 1982 aimed to determine the feasibility of laboratory study of spawning behavior in the laboratory. Other 1982 experiments examined the effects of oil exposure on free gametes (sperm and eggs before fertilization) and the fertilized eggs attached to substrate. In 1983, efforts focused on exposure of attached eggs to fresh oil and a simulated weathered oil.

The 1982 work on spawning behavior demonstrated the feasibility and importance of further behavioral research. Spawning behavior was successfully induced in the laboratory with an extract from the male reproductive organ. Herring actively tested the available substrate types before egg deposition and showed definite preferences for certain depositional substrates. The active substrate testing and definite substrate Preferences indicate a potential ability for herring to choose clean over contaminated substrate. Further behavioral research is necessary to demonstrate such an adaptive capability.

In 1982, no effect of oil exposure on free gametes was observed. Unfertilized eggs exposed for 2 h to oil-contaminated seawater before transfer to clean seawater containing unexposed, viable sperm showed no difference from unexposed eggs in fertilization rates. Similarly, exposure of sperm and eggs together showed no treatment effects on fertilization rate.

In both 1982 and 1983, no effect on total hatch from attached eggs was observed. After continuously flowing exposure of attached eggs for 24 h during the first 29 h following fertilization, there was no effect on the total percentage of eggs hatching successfully in any experimental treatment: unfiltered undispersed fresh Prudhoe Bay crude oil, filtered undispersed fresh oil, chemically-dispersed fresh oil, filtered undispersed fractionated (Stage I) oil, and chemically-dispersed fractionated (Stage I) oil. The fractionated oil was used to simulate weathered spilled oil. The highest exposure to total oil was 28 ppm total hydrocarbons measured by infrared (IR) spectrophotometry in the 1983 unfiltered undispersed fresh oil treatment. The highest exposure to monoaromatic hydrocarbons was 4.7 ppm measured by helium equilibration gas chromatography (HeGC) in the 1983 filtered undispersed fresh oil treatment. In both years, some crosses between donor fish produced eggs with much lower hatching rates than others. These lower hatching rates were not due to a failure to be fertilized but to some unknown process causing mortality in the developing embryos. The experimental design of any future experiments concerning the effects of any contaminant on herring eggs must take into account the substantial influence of donor cross.

In both 1982 and 1983, there was an effect of oil exposure on the larval fish hatching from exposed eggs. Oil exposure significantly increased the frequency of abnormal larvae in both years. Donor crosses also differed significantly in the frequency of abnormal larvae but did so independently of differences in total hatch. The larval abnormalities observed, e.g., spinal deformities, swollen pericardial regions, and yolk sac compartmentalization, would impair larval survival. The unfiltered undispersed fresh oil treatments, in which substantial oil was present as droplets that adhered to the attached eggs, were the most severe treatments. Both filtered treatments, which had little or no oil adhering to eggs, showed frequencies of abnormal larvae that did not exceed the range of natural variation in controls. Chemically dispersed fresh oil in 1982 showed lower frequences of abnormal larvae than undispersed unfiltered fresh oil at comparable concentrations of hydrocarbons in the water column, However, confirmation of beneficial effects from chemical dispersants needs further study.

The amount of oil adhering to eggs apparently was the major determinant of the frequency of abnormal larvae. Even with substantial concentrations of toxic monoaromatic hydrocarbons (up to 47 ppm by HeGC), treatments with little or no visible oil on eggs did not produce frequencies of abnormal larvae beyond natural variability. Oil on eggs could have acted both to enhance entry of toxic components into eggs and to disrupt gaseous exchange across egg membranes by coating egg surfaces.

A finding with definite implications for environmental management was that water concentrations of specific or total hydrocarbons could be poor or misleading indicators of the frequency of abnormal larvae. In the 1983 exposure experiment, the water concentration of total saturates determined by glass capillary gas chromatography was the single best predictor of the frequency of abnormal larvae. Surprisingly the water concentration of more toxic monoaromatic hydrocarbons was not significantly correlated with larval effects. Assessment of impacts on attached eggs from water column concentrations of hydrocarbons can be misleading because apparently it is the dose of oil received by eggs from adhering oil droplets rather than from hydrocarbons in the water water column that most heavily and directly affects the larvae hatching from attached eggs.

The present study indicates that the aspect of hatching success of Pacific herring most likely to be impacted by oil exposure is the frequency of abnormal larvae. Increased frequencies of abnormal larvae were observed for undispersed fresh oil at concentrations of total hydrocarbons determined by helium equilibration and glass capillary gas chromatography to be 0.004 ppm in 1982 and 0.761 ppm in 1983. Where turbulence physically disperses spilled oil in to the water column, hydrocarbon concentrations exceeding 1.0 ppm have been observed (Calder and Boehm, 1981). The year-to-year variation of oil-in-water concentrations that produced increased frequency of abnormal larvae appeared to be due to differences in the amount of oil present in the water column as droplets. The oil spill situation most likely to impact herring reproductive success is one in which fresh oil is physically dispersed into the water column by turbulence and, subsequently, adheres as droplets to attached herring eggs.