s eafoods would dis appear from our tables. Even among fishes that range widely in coastal
waters , many depe nd upon protected ins hore areas to s erve as nurs ery and feeding grounds for
their young. Baby tarpon are abundant in all that labyrinth of mangrove-lined s treams and
canals borderi ng the lower third of the wes tern coas t of Florida. On the Atlantic Coas t the s ea
tro ut, c roake r, s pot, an d d ru m s pawn on s andy s hoals off the inlets between the is lands or
‘banks’ that lie like a protective chain off much of the coast s outh of New York. The young fis h
hatch and are carried through the inlets by the tides. In the bays and s ounds— Currituck,
Pamlico, Bogue, and many others—the y find abundant food and grow rapidly. Without thes e
nurs ery areas of warm protec ted, food-rich wate rs the populations of thes e and many other
s pecies could not be maintained. Yet we are allowing pesticides to enter them via the rivers and
by direct s praying over borde ring mars hlands. And the early s tages of these fishes, even more
than the adults, are especially susceptible to direct chemical poisoning. Shrimp, too, de pend on
ins hore feeding grounds for their young. One abundant and widely ranging s pecies s upports the
entire commercial fis hery of the s outhe rn A tlantic and Gulf s tates. Although s pawning occurs at
s ea, the young come into the es tuaries and bays when a few weeks old to undergo s uccess ive
molts and changes of form. There the y remain fro m May or June until fall, feeding on the
bottom detritus. In the entire pe riod of their i ns hore life, the welfare of the s hri mp populations
and of the indus try they s upport depe nds upon favorable conditi ons in the es tuaries.
Do pes ticides repres ent a threat to the s hrimp fis heries and to the s upply for the markets? The
ans wer may be contained in recent laboratory expe rime nts carried out by the Bureau of
Commercial Fisheries. The insecticide tolerance of young commercial shrimp just past larval life
was found to be exceedingly low—meas ured in parts per billion instead of the more commonly
us ed s tandard of parts per million. For example, half the s hrimp in one experiment were killed
by dieldrin at a concentration of only 15 per billion. Other chemicals were even more toxic.
Endrin, always one of the mos t deadly of the pesticides, killed half the shrimp at a
concentration of only half of one part per billion. The threat to oysters and clams is multiple.
Again, the young s tages are mos t vulnerable. Thes e s hellfis h inhabit the bottoms of bays and
sounds and tidal rivers from New England to Texas and sheltered areas of the Pacific Coast.
Although s edentary in adult life, they discharge their s pawn into the s ea, where the young are
free-living for a period of several weeks. On a summer day a fine-mes hed tow net drawn be hind
a boat will collect, along with the other drifting plant and animal life that make up the plankton,
the infinitely small, fragile-as -glass larvae of oysters and clams. No larger than grains of dus t,
these transparent larvae swim about in the surface waters, feeding on the microscopic plant life
of the plankton. If the crop of minute s ea vegetation fails , the young s hellfis h will s tarve. Yet
pesticides may well destroy substantial quantities of plankton. Some of the herbicides in
common us e on lawns , cultivated fields , and roads ides and even in coastal marshes are
extraordinarily toxic to the plant plankton which the larval mollusks use as food—s ome a t only
a few parts per billion.
The delicate larvae themselves are killed by very small quantities of many of the common
ins ecticides. Even expos ures to les s than lethal quantities may in the end caus e death of the
larvae, for inevitably the growth rate is retarded. This prolongs the period the larvae mus t
s pend in the haza rdous worl d of the plankton and s o decreas es the chance they will live to
adulthood. For adult mollusks there is apparently less danger of direct poisoning, at least by
s ome of the pes ticides. This is not neces sarily reas s uring, however. Oysters and clams may
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