have serious consequences for adult populations over the long
run, and such consequences may be difficult to detect, although a
recently developed physical model () suggests that they would be
minimal. Also unknown are the long-term effects of trace
contamination of fishes through feeding. Many fishes feed on
benthic invertebrates that may contain petroleum hydrocarbons from
the sediment. Others, such as mullet, feed on organisms and
detritus at the water's surface, where there may also be
hydrocarbon concentrations. Mullet in some Australian coastal
waters close to port and refinery facilities are frequently
contaminated with petroleum hydrocarbons having an odor and
chemical composition similar to kerosene ().
FISHERIES
In addition
to killing some organisms outright, oil pollution may otherwise
affect the use of commercial species of fish, molluscs, and
crustaceans. Even though no direct effects of oil on fishes were
observed in Santa Barbara Channel (), the risk of fouling fishing
gear or catching contaminated fish severely reduced fishing effort.
This had an economic impact on the local fisherman, even though the
resource was not directly affected ().
Tainting of
commercial species of fish (), clams (), oysters (), and mussels ()
by oil has been frequently reported. This results in unsaleable
catches. Tainting may be quite persistent, the noticeable taint
lasting several months. Furthermore, Blumer et al. () have
indicated that oysters affected by the West Falmouth spill, but
subsequently kept in clean water, retained petroleum hydrocarbons
similar in chemical composition to the Number 2 fuel oil spilled
for over eight months. Based on these findings, authorities imposed
a total ban on the taking of shellfish in a large area. A partial
ban still exists more than three years after the original
contamination. Ehrhardt (), considering Blumer's findings, his own
findings on heavy petroleum contamination of Galveston Bay oysters,
and the kerosene-like tainting of Australian mullet (), concluded
that organisms accumulate, quite unspecifically, the entire range
of hydrocarbons to which they are exposed.
More recent
research indicates that shellfish () and fish () will accumulate
hydrocarbons from solution but will rapidly (certainly within a few
months) shed them if maintained in uncontaminated seawater.
Blumer's conclusion that petroleum hydrocarbons will persist
without much modification or reduction for many months in the fatty
tissue of shellfish thus seems oversimplified. The mechanisms of
uptake and of decontamination are complex and varied and the time
required for decontamination probably depends on the duration and
dosage of exposure, on storage sites, on whether the species
involved possesses the metabolic processes to detoxify the
hydrocarbons, and on the organisms' physiological state and other
factors.
Attempts have
been made to demonstrate the effects, or lack