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Fish
Monitoring the health of fish in streams, rivers, lakes, and estuaries
is important for several reasons. Fish are an excellent indicator
species since they are at the top of the food web and tend to integrate
effects observed in lower trophic levels. In addition, fish have
a high economic value and impacts to fish populations can significantly
influence the food chain. Effects on fish can be measured at the
cellular level, the individual level (i.e. to obtain tissue metals
concentrations, health and condition), the population level (i.e.
changes in growth and fertility), and the community level (i.e.
ecological effects such as changes in species composition, relative
abundance and distribution). The decision to measure effects at
the cellular, individual, population, or community level will depend
upon study objectives.
Fish are sampled during baseline monitoring programs to document
species composition, population size, and document population characteristics
(i.e. length-weight relationships, age-structure, sex ratio, fertility,
growth). Sampling fish tissue to determine metals concentrations
is also common. Information on population characteristics and metals
concentrations is collected before, during, and after closure of
the mine in order to track environmental impacts (MEND,
2001).
Stream and River Sampling
Measuring fish population abundance in streams is usually accomplished
by removal methods that involve temporarily removing the majority
of fish in a small reach. The most common methods are beach seining
(where possible) and electro-fishing. Beach seining is accomplished
by setting nets in a reach (i.e. 100 m) to prevent immigration and
emigration of fish and conducting sweeps of the reach to enumerate
all fish. Fish are returned to the stream once sampling has been
completed and changes in abundance over time are monitored. Electro-fishing
can be used in conjunction with beach seining. Electro-fishing is
generally conducted by boat and can access difficult locations (i.e.
narrow streams and rivers) that are difficult to access using beach
seining alone. Individual fish can be acquired from each of the
capture methods to measure tissue metal concentrations (MEND,
2001).
Lake and Estuary Sampling
The abundance and condition of fish populations in lakes and estuaries
are usually measured using nets (e.g. gill nets and trap nets) and
by angling. Studies conducted in large waterbodies are normally
focused at the population or community level, and not at the individual
level. To determine possible effects on fish populations or communities,
information on species composition, abundance, and distribution
of fish is required. This requires that many fish must be captured
from a relatively large area using quantitative, non-destructive
techniques. For example, changes in relative abundance of lake,
estuarine and marine fish populations are generally estimated using
catch-per-unit-effort (CPUE) statistics (i.e. number of fish captured
per 100 m of net per hour). The same areas are fished repeatedly
over time to determine changes in the number of fish captured per
unit time. Changes in CPUE are indicative of changes in fish species
composition and relative abundance at the community level. In addition,
changes at the population level such as growth, fertility, condition
factor, and age-frequency distribution can be used to determine
effects. Such studies are normally conducted over long time periods
and require specialized knowledge. Fish for tissue analyses can
be collected using any of the methods used for population sampling.
Minnow traps target smaller fish that are not easily sampled with
nets and may be appropriate for use in some lakes (MEND,
2001).
Problem | Compliance
| Health & Safety | Sampling
| Analytical | Data
Quality
Site Assessment | Prediction
| Construction | GIS
| Monitoring & Assessment
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