Page 774 - Veterinary Toxicology, Basic and Clinical Principles, 3rd Edition

P. 774

VetBooks.ir Chapter 54

Aquatic Toxicology

Robert W. Coppock and P. Nick Nation

INTRODUCTION BACKGROUND
This chapter focuses on aquatic toxicology of fish culture. Fish are cultured in some form of confinement such as a
Aquaculture is the production of aquatic animals in the pen, pond, or tank. Cultured fish are usually dependent on
aquatic environment for human food, replenishing fish humans for part or all of their feed and can be entirely
stocks and other uses. The water may be a sheltered oce- dependent on humans for maintenance of their ecosystem.
anic bay containing penned organisms, inland ponds or an Inland aquaculture often requires at least some amount of
indoor tank system. The more contained the aquatic rear- mechanical-hydrological management to maintain the
ing system, the more diligent must be monitoring and aquatic environment. Large capital investment and high
controls over the artificial ecosystem. The smaller the vol- operational costs are incentives to maximize stocking den-
ume of water and the more contained the system is, the sities in aquaculture systems. Increased stocking densities
more susceptible it is to water safety issues. Issues in increase sophistication and attention to details required
water safety can contribute to outbreaks of infectious dis- for water management.
eases. The hobbyist also raises or maintains fish and other
aquatic animals/plants in a variety of integrated ecosys-
tems. Fish are also used as public displays by commercial WATER SAFETY
organizations.
Chemical and physical causes of disease in aquatic Water safety is essential for maintaining healthy life.
organisms are generally linked to water and food because Upstream users and incidents can contaminate the water
these are the primary pathways of toxic substances to ani- source for aquaculture. Rainstorm events creating exces-
mals in the aquatic environment. Noise pollution is being sive surface runoff, and fires and chemical spills can con-
shown to be an important physical agent (NAS, 2016). taminate water sources. Unsafe water kills more fish in
Intoxication of fish can be acute, subacute, or chronic. tanks and ponds than all other causes of mortality. The
Chemical-linked food safety issues can occur if chemical biology of fish can directly affect safety of the water in
contamination of edible aquatic organisms occurs. The tox- which they live, and their metabolic activity interacting
icity of a specific substance can vary between fish species with other aquatic biota can move water parameters from
and can change with water temperature, pH, and ion com- safe to unsafe. This is particularly true in recirculating
position (Wlasow et al., 2010). In recirculation systems, systems and at high stocking densities. Sensitivity to
waste materials and microbial degradation products can water parameters in aquaculture varies with age of the
reach toxic levels. Chemical intoxication and other envi- fish and stage of development (Finn, 2007). Water para-
ronmental stressors can increase the susceptibility of meters are interactive and dynamic, and changing one
aquatic organisms to infectious diseases (Morley, 2010). parameter always affects other factors. For example, the
The predisposing causes of infectious disease and larval pH of water is important in affecting the solubility of
survival can be overlooked because they may be subtle or metals (Finn, 2007). Increasing the pH generally
unrecognized. The toxicology of the water column differs decreases the bioavailability of metals by increasing com-
from that of the sediment, and these variations in the plexes with organic matter in the water. Temperature of
aquatic environment present different issues to various seg- the water is important, and the ideal temperature can vary
ments of the aquaculture industry (Rudolph et al., 2009). with life stage and genera.

769 770 771 772 773 774 775 776 777 778 779