Page 779 - Veterinary Toxicology, Basic and Clinical Principles, 3rd Edition

738 SECTION | X Avian and Aquatic Toxicology

VetBooks.ir Jacobsen, 2009). ZEA, an estrogen mimic, is also present ACOUSTIC POLLUTION AND FISH
in runoff waters from wheat and maize fields. The effect
Sound propagation in water is strongly affected by tem-
of ZEA in fish can be contradictory depending on species,
life stage, dose and duration of exposure. Decreased perature, pressure, and to a lesser extent, by salinity
(NOAA, 2000). Low frequency sound can be propagated
spawning frequency and increased plasma vitellogenin is
long distances in water. Fish use sound sensors for many
observed in zebra fish. ZEA alters iron metabolism and
interactions with their ambient environment and interac-
clotting time in rainbow trout. ZEA alters in vitro immune
tions with each other (NAS, 2016). Pressure sensors are
functions of leukocytes harvested from the head and trunk
also important for locomotion in the aquatic environment.
kidney of fish fed low dietary levels (332 μg/kg of feed)
Noise pollution can mask or shift hearing thresholds,
by upregulation and downregulates these functions at
damage auditory organs and cause adverse stress
higher doses ($0.621 μg/kg of feed). Oxygen consump-
responses (Peng et al., 2015). Exposure of fish to noise
tion is increased in carp exposed to dietary levels
during embryo and larval stages can cause decreased sur-
($0.621 μg/kg of feed for 4 weeks).
vival (Brown et al., 2016). Reduction in ability to monitor
the aquatic environment is a plausible explanation.
Aflatoxins
CONCLUDING REMARKS AND FUTURE
Fish feeds can be contaminated with AFs. (see DIRECTIONS
Chapter 69: Aflatoxins). AFB 1 is activated by the CYP
enzymes in fish and important detoxification pathways Fish are being concentrated for aquaculture, breeding, dis-
in fish are the uridine diphosphate glucuronyl- play, and similar human-directed activities. The culture of
transferase and, to a lesser extent, glutathione S- an increasingly wide range of aquatic organisms for food
transferase pathway. Rainbow trout are one of the most is accelerating worldwide. Fish offal and oil are an impor-
sensitive species to the carcinogenic effects of aflatox- tant raw material for animal feeds and can be source-
ins and carp are a relatively resistant species. Aflatoxins persistent organic chemicals that are bioconcentrated in
also cause hepatocellular necrosis and fibrosis. body fat. Increasing artificiality of the aquatic environ-
Differences in biotransformation of AFs likely explain ment also increases the monitoring required to maintain
the differences in species sensitivity. AFs are rapidly water safety. The safety of input water and feeds is impor-
excreted and are not known to be biomagnified in edible tant in maintaining the health of aquatic organisms being
fish tissues. Aflatoxicol and AFM 1 are the primary cultured and the safety of foods and byproducts being
metabolites of fish that are excreted into water. Dietary produced. Multiple competing uses of water resources
ascorbic acid is protective against AFs. Aflatoxins target provide an ongoing challenge to aquaculture. Securing
both the innate and adaptive immune functions. There is rights for incoming water supplies is becoming increasingly
some evidence that immune memory is decreased by competitive as are increasing requirements to return the out-
exposure to AFs. Hematocrit may be reduced in fish flow water to the environment in acceptable condition. Food
exposed to dietary AFs and hepatic enzymes in serum and feed safety are increasing issues that requires coopera-
are also increased. tion among all the industries involved with aquaculture. An
additional future research need is for rapid and accurate
diagnostics in diseases caused by chemical and physical
agents.
CONTAMINANTS IN AQUACULTURE FISH
Aquaculture animals are an important dietary source of REFERENCES
environmentally persistent organic chemicals. These per-
sistent chemicals are biomagnified in fish and animals Aggergaard, S., Jensen, F.B., 2001. Cardiovascular changes and physio-
consuming these products. including offal incorporated logical response during nitrite exposure in rainbow trout. J. Fish
into pet foods. These compounds are also transferred to Biol. 59, 13 27.
the human fetus during pregnancy and excreted in breast Benli, A.C., Koksal, G., Ozkul, A., 2008. Sublethal ammonia exposure
of Nile tilapia (Oreochromis niloticus L.): effects on gill, liver and
milk during lactation. The most sensitive life stage,
kidney histology. Chemosphere. 72, 1355 1358.
including humans, for adverse effects is the prenatal and
Berntssen, M.H.G., Hylland, K., Julshamn, K., et al., 2004. Maximum
early postnatal period. Endocrine disruption and epige-
limits of organic and inorganic mercury in fish feed. Aquacul. Nutr.
netic effects have been observed depending of the specific
10, 83 97.
chemical and animal species. Dietary animal protein, fat, Brown, A.D., Sisneros, J.A., Jurasin, T., et al., 2016. Effects of hatchery
and clays are the predominant source of POCs for cul- rearing on the structure and function of salmonid mechanosensory
tured fish. systems. Adv. Exp. Med. Biol. 875, 117 124.