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Effects of Electrofishing Fields on Captive Embryos and Larvae of Razorback Sucker
Author(s) -
Muth Robert T.,
Ruppert Jack B.
Publication year - 1997
Publication title -
north american journal of fisheries management
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.587
H-Index - 72
eISSN - 1548-8675
pISSN - 0275-5947
DOI - 10.1577/1548-8675(1997)017<0160:eoefoc>2.3.co;2
Subject(s) - hatching , biology , embryo , zoology , epiboly , electrofishing , larva , duty cycle , andrology , anatomy , embryogenesis , ecology , voltage , fishery , physics , medicine , abundance (ecology) , gastrulation , quantum mechanics
In the laboratory, we assessed the effects of electroshocking embryos and early larvae of razorback sucker Xyrauchen texanus with square‐wave pulsed DC in homogeneous fields. Embryos at early epiboly, early tail bud, or fin fold developmental stages and pre‐swim‐up larvae were exposed for 10 s to simple pulse currents of 30 Hz (l2% duty cycle), 60 Hz (24% duty cycle), or 80 Hz (40% duty cycle), or to a fixed complex pulse current of three 240‐Hz, 2.6‐ms pulses delivered at 15 Hz (12% duty cycle). Peak‐voltage gradient for each current was 1.2 V/cm (power density = 936 μW/cm 3 ). Tests were also conducted with the 60‐Hz current at peak‐voltage gradients of 5.0 V/cm (16,250 μW/cm 3 ) and 10.0 V/cm (65,000 μW/cm 3 ). Survival of embryos from treatment through hatching improved significantly ( P ≤ 0.05) at successive developmental stages; embryos at early epiboly were most sensitive to electric shock. Mean survival of embryos at each developmental stage was significantly greater ( P ≤ 0.05) in controls than in all treatments, except those with the 30‐Hz or complex pulse currents at early tail bud and fin fold. Within the 60‐Hz treatments at each developmental stage, survival of embryos decreased with increasing peak‐voltage gradient. Survival of larvae through 4 weeks after treatment was not affected by exposure to electric current, but mean growth of control larvae was significantly greater ( P ≤ 0.05) than that of larvae in all treatments. Mean growth of larvae was not significantly different among treatments. Results suggest that electrofishing spawning aggregations of razorback sucker could harm developing embryos and early larvae if they are subjected to electric‐field intensities greater than l V/cm.