Biological field and laboratory methods for measuring the quality of ...
Biological field and laboratory methods for measuring the quality of ...
Biological field and laboratory methods for measuring the quality of ...
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4.0 SAMPLE ANALYSIS<br />
4.1 Data Recording<br />
The sample records should include collection<br />
number, name <strong>of</strong> water body, date, locality, <strong>and</strong><br />
o<strong>the</strong>r pertinent in<strong>for</strong>mation associated with <strong>the</strong><br />
sample. Make adequate <strong>field</strong> notes <strong>for</strong> each collection.<br />
Write with water-pro<strong>of</strong> ink <strong>and</strong> paper to<br />
ensure a permanent record. Place <strong>the</strong> label inside<br />
<strong>the</strong> container with <strong>the</strong> specimens <strong>and</strong> have <strong>the</strong><br />
label bear <strong>the</strong> same number or designation as <strong>the</strong><br />
<strong>field</strong> notes, including <strong>the</strong> locality, date, <strong>and</strong> collector's<br />
name. Place a numbered tag on <strong>the</strong> outside<br />
<strong>of</strong> <strong>the</strong> container to make it easier to find a<br />
particular collection. Place any detailed observations<br />
about a collection on <strong>the</strong> <strong>field</strong> data sheet.<br />
Record fishery catch data in st<strong>and</strong>ard units such<br />
as number or weight per area or unit <strong>of</strong> ef<strong>for</strong>t.<br />
Use <strong>the</strong> metric system <strong>for</strong> length <strong>and</strong> weight<br />
measurements.<br />
4.2 Identification<br />
Proper identification <strong>of</strong> fishes to species is important<br />
in analysis <strong>of</strong> <strong>the</strong> data <strong>for</strong> water <strong>quality</strong><br />
interpretation. A list <strong>of</strong> regional <strong>and</strong> national<br />
references <strong>for</strong> fish identification is located at <strong>the</strong><br />
end <strong>of</strong> this chapter. Assistance in confirming<br />
questionable identification is available from<br />
State, Federal, <strong>and</strong> university fishery scientists.<br />
4.3 Age, Growth, <strong>and</strong> Condition<br />
Changes in water <strong>quality</strong> can be detected by<br />
studying <strong>the</strong> growth rate <strong>of</strong> fishes. Basic<br />
<strong>methods</strong> used to determine <strong>the</strong> age <strong>and</strong> growth<br />
<strong>of</strong> fish include:<br />
• Study <strong>of</strong> fish length-frequencies, <strong>and</strong><br />
• Study <strong>of</strong> seasonal ring <strong>for</strong>mations in hard<br />
bony parts such as scales <strong>and</strong> bones.<br />
The length-frequency method <strong>of</strong> age determination<br />
depends on <strong>the</strong> fact that fish size varies<br />
with age. When <strong>the</strong> number <strong>of</strong> fish per length<br />
interval is plotted on graph paper, peaks generally<br />
appear <strong>for</strong> each age group. This method<br />
works best <strong>for</strong> young fish.<br />
The seasonal ring-<strong>for</strong>mation method depends<br />
on <strong>the</strong> fact that fish are cold-blooded animals<br />
<strong>and</strong> <strong>the</strong> rates <strong>of</strong> <strong>the</strong>ir body processes are affected<br />
11<br />
FISH IDENTIFICATION<br />
by <strong>the</strong> temperature <strong>of</strong> <strong>the</strong> water in which <strong>the</strong>y<br />
live. Growth is rapid during <strong>the</strong> warm season <strong>and</strong><br />
slows greatly or stops in winter. This seasonal<br />
change in growth rate <strong>of</strong> fishes is <strong>of</strong>ten reflected<br />
in zones or b<strong>and</strong>s (annual rings) in hard bony<br />
structures, such as scales, otoliths (ear stone),<br />
<strong>and</strong> vertebrae. The scales <strong>of</strong> fish may indicate<br />
exposure to adverse conditions such as injury,<br />
poor food supply, disease, <strong>and</strong> possibly water<br />
<strong>quality</strong>.<br />
Note <strong>the</strong> general well being <strong>of</strong> <strong>the</strong> fish - do<br />
<strong>the</strong>y appear emaciated? diseased from fungus?<br />
have open sores, ulcers, or fin rot? parasitized?<br />
Check <strong>the</strong> gill condition, also. Healthy fish will<br />
be active when h<strong>and</strong>led, reasonably plump, <strong>and</strong><br />
not diseased. Dissect a few specimens <strong>and</strong> check<br />
<strong>the</strong> internal organs <strong>for</strong> disease or parasites. The<br />
stomachs can be checked at this time to determine<br />
if <strong>the</strong> fish are actively feeding.<br />
5.0 SPECIAL TECHNIQUES<br />
5.1 Flesh Tainting<br />
Sublethal concentrations <strong>of</strong> chemicals, such as<br />
phenols, benzene, oil, 2, 4-D, are <strong>of</strong>ten responsible<br />
<strong>for</strong> imparting an unpleasant taste to fish<br />
flesh, even when present in very low concentrations.<br />
Flesh tainting is nearly as detrimental to<br />
<strong>the</strong> fisheries as a complete kill.<br />
A method has been developed (Thomas,<br />
1969) in which untainted fish are placed in cages<br />
upstream <strong>and</strong> downstream from suspected waste<br />
sources. This procedure will successfully relate<br />
<strong>the</strong> unacceptable flavor produced in native fish<br />
if exposed to a particular waste source.<br />
To ensure uni<strong>for</strong>m taste <strong>quality</strong> be<strong>for</strong>e exposure,<br />
all fish are held in pollution-free water <strong>for</strong><br />
a IO-day period. After this period, a minimum<br />
<strong>of</strong> three fish are cleaned <strong>and</strong> frozen with dry ice<br />
as control fish. Test fish are <strong>the</strong>n transferred to<br />
<strong>the</strong> test sites, <strong>and</strong> a minimum <strong>of</strong> three fish are<br />
placed in each portable cage. The cages are suspended<br />
at a depth <strong>of</strong> 0.6 meter <strong>for</strong> 48 to 96<br />
hours.<br />
After exposure, <strong>the</strong> fish are dressed, frozen on<br />
dry ice, <strong>and</strong> stored to OaF until tested. The control<br />
<strong>and</strong> exposed samples are shipped to a fishtasting<br />
panel, such as is available at <strong>the</strong> food<br />
science <strong>and</strong> technology departments in many <strong>of</strong>