Page 696 - The Toxicology of Fishes

676 The Toxicology of Fishes

TABLE 15.3
Endpoints Measured in Subchronic and Chronic Exposure Tests
with Fish at Different Stages
F 0 embryo
Incubation time from fertilization to hatch
Hatching time required for embryos to hatch
Time from complete hatch to first feeding
Percentage of normal and abnormal larvae at complete hatch
Weight of larvae at complete hatch
F 0 larvae and juveniles
Abnormal behavior
Total percentage of deformed fish
Percent survival
Weights/lengths of juveniles
Number of juveniles that develop to sexual maturation and develop
secondary sex characteristics
F 1 embryos
Number of eggs produced by sexually mature fish
Number of viable embryos (F 1 ); hatching, survival, and growth of F 1

The specific environmental conditions and measurements in acute fish tests are delineated in the
standardized tests. Early work with acute toxicity tests relied on reporting nominal concentrations of
chemicals (based on stock solution calculations), rather than concentrations based on analytical mea-
surements. All acute definitive tests should be based on measured concentrations. When possible,
chemical residues in fish tissue should also be measured. This will provide data to equate lethal body
residues with acute toxicity endpoints (e.g., LC , LC ) under optimum conditions of bioavailability. It
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will further enable one to evaluate the meaning of realistic environmental exposure concentrations (EECs)
of chemicals.
In analyzing acute toxicity data, the time to death (i.e., survival time) or duration of exposure before
death should also be obtained (Sprague, 1969) to determine the probability of dying during a given
interval. This is especially relevant for acute exposures that typically occur in the environment. This
endpoint will become more applicable when acute exposures in the laboratory implement procedures
that incorporate different natural waters (e.g., oligotrophic, mesotrophic, and eutrophic) and sediment
into acute testing procedures. To date, acute toxicity tests with fish have used laboratory-filtered waters
without sediment.

Chronic Toxicity Tests
Objectives of subchronic and chronic exposure tests are listed in Table 15.3. As pointed out earlier, in
full life-cycle chronic tests the test organisms are exposed for an entire reproductive life cycle (egg to
egg) to at least five concentrations of test substance. Partial life-cycle tests involve several sensitive life
stages and include reproduction and growth during the first year but do not include early juvenile stages.
In full chronic tests, exposure may start with the egg or zygote and continue through development and
hatching of the embryo, growth and development of the young organism, attainment of sexual maturity,
and reproduction to produce a second-generation organism. Tests may also begin with the exposed adult
and continue through egg production, fry, juvenile, and adult to egg. Effect criteria include growth at
different stages, reproduction, development of gametes, maturation, spawning success, hatching success,
survival of larvae or fry, growth and survival of different life stages, and behavior. Specific endpoints
measured in subchronic and chronic tests are listed in Table 15.3.
Hypothesis testing is used to detect statistical differences in effect criteria data generated from chronic
tests. Data are analyzed to determine whether responses at different exposure concentrations are different
from control (or solvent) responses. The experimental design most often used in hypothesis testing for
chronic data is a one-way analysis of variance (ANOVA). A series of treatment concentrations are