The minimum immediate overall kill throughout the ma rs hes , exclus ive of the Indian River
shoreline, was 20-30 tons of fishes, or about 1,175,000 fishes, of at least 30 species [reporte d R.
W. Harrington, J r. and W.L. Bidlingmayer of the survey tea m]. Mollus ks s eemed to be
unharme d by dieldrin. Crus taceans were virtually exterminated throughout the area. The entire
aquatic crab population was apparently des troyed and the fiddler crabs , all but annihilated,
survived temporarily only in patches of mars h evidently miss ed by the pellets. The larg er g a me
and food fis hes s uccumbed mos t rapi dly...Crabs net upon and des troyed the moribund fis hes ,
but the next day were dead the ms elves. Snails continued to devour fis h carcass es. After two
weeks , no trace re mained of the litter of dead fishes. The s a me melancholy picture was painted
by the late Dr. Herbert R. Mills from his observations in Tampa Bay on the oppos ite coas t of
Florida, where the National Audubon Society operates a sanctuary for seabirds in the area
including Whis key Stump Key. The s anctuary ironically became a poor refuge after the local
health authori ties undertook a campaign to wipe out the salt-mars h mos quitoes. Again fis hes
and crabs were the principal victims. The fiddler crab, that s mall and pictures que crus tacean
whos e hordes move ove r mud flats or sand flats like grazing cattle, has no defense against the
s prayers. After s ucces sive s prayings during the s umme r and fall months (s ome areas were
sprayed as many as 16 times ), the s tate of the fiddler crabs was s ummed up by Dr. Mills : ‘A
progressive scarcity of fiddlers had by this time become appare nt. W here there s hould have
been in the neighborhood of 100,00 0 fiddlers under the tide and weather conditions of the day
[October 12] the re were not ove r 100 which could be s een anywhere on the beach, and thes e
were all dead or sick, quivering, twitching, stumbling, scarcely able to crawl; although in
neighbori ng uns prayed areas fiddlers were plentiful.’
The place of the fiddler crab in the ecol ogy of the world it inhabits is a necessary one, not easily
filled. It is an important s ource of food for many ani mals. Coas tal raccoons feed on the m. So do
ma rs h-inhabiting birds like the clapper rail, s hore- birds , and even visiting s eabirds. In the New
Jers ey s alt mars h s prayed with DDT, the normal population of laughing gulls was decreas ed by
85 per cent f or s everal weeks , pres umably becaus e the birds could not find s ufficient food after
the spraying. The marsh fiddlers are important in other ways as well, being useful scavengers
and aerating the mud of the mars hes by their exte ns ive burrowings. They als o furnis h
quantities of bait for fis herme n. The fiddler crab is not the only creature of tidal marsh and
es tuary to be threatene d by pes ticides ; others of more obvious importance to man are
endangered. The famous blue crab of the Chesapeake Bay and other Atlantic Coast areas is an
example. These crabs are so highly susceptible to insecticides that every spraying of creeks,
ditches , and ponds in tidal marshes kills most of the crabs living there. Not only do the local
crabs die, but others moving into a s prayed area from the s ea s uccumb to the lingering pois on.
And s ome times pois oning may be indi rect, as in the mars hes near Indian River, where
s cavenger crabs attacked the dying fis hes , but s oon thems elves s uccumbed to the pois on. Less
is known about the haza rd to the lobs ter. H oweve r, it bel ongs to the s ame group of arthropods
as the blue crab, has ess entially the s ame phys iology, and would pres umably s uffer the s ame
effects. This would be true als o of the s tone crab and other crus taceans which have direct
economic importance as human food.
The ins hore wate rs—the bays , the s ounds , the river es tuaries , the tidal mars hes—fo rm a n
ecological unit of the utmos t importance. They are linked so intimately and indispensably with
the lives of many fishes, mollusks, and crustaceans that were they no longer habitable thes e
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