Effects Of Electrofishing Research Articles

Autumn electrofishing reduces harm to Ontario (Canada) stream fishes collected during watershed health monitoring

Electrofishing surveys provide important information on watershed health, and the status of imperiled and recreationally important stream fishes. Concerns about the harmful effects of electrofishing on the endangered redside dace Clinostomus elongatus have resulted in restrictions on its use in sampling activities in the province of Ontario, Canada. However, the effectiveness of these restrictions is unproven. We undertook a paired sampling gear study in 2018-2019 to test whether an alternate gear (seine nets) or a change in electrofishing timing (autumn rather than summer) reduced harm to stream fishes. The study took place in streams located in the Greater Toronto Area. We found large differences in the frequency and magnitude of sampling-related mortalities between sampling gear and seasons. During individual surveys, electrofishing mortality never exceeded 9% in the summer or 4% in the autumn, while seining-related mortality reached 60% at two stream sites. Overall, autumn electrofishing resulted in mortality rates that were 5.6 and 15 times lower than summer electrofishing and summer seining. These results indicate that survival of Ontario stream fishes can be improved by delaying electrofishing until early autumn.

Effects of electrofishing on stress response of wild carp (Cyprinus carpio, L.)

Electrofishing is commonly used by fishery scientists for collecting fishes. During such work, fishes are often exposed to air for several minutes which lead to deleterious impacts. The purpose of the current paper was to compare hematological and biochemical parameters of wild carp when electrofishing device was applied. Hematology and serum biochemical analyses were performed. The result showed significant differences (p < 0.05) in white blood cells (WBC), cortisol, glucose, total protein, albumin, globulin, and albumin-globulin ratio between control and treatment groups. Also, electrofishing caused an increase in cortisol, glucose, cholesterol, albumin, albumin-globulin ratio, Ca2+, and Cl− levels, but decreased lactate, triglyceride, total protein, globulin, Mg2+, and Na+ levels. It can be deduced from this study that electrofishing method for fish capture provide stressful condition which subsequently influential on body homeostasis through some biochemical factors.

&amp;lt;i&amp;gt;In Vitro&amp;lt;/i&amp;gt; Chromosomal Aberration Frequency by Electrofishing on &amp;lt;i&amp;gt;Poecilia latipinna&amp;lt;/i&amp;gt; (Sailfin Molly) Fishes in Southern of Iraq

The present studies describe Chromosomal aberration effects of electrofishing, which were evaluated on Poecilia latipinna, located in Shat Al-Arab river in Al-garmma city (south of Iraq). The electrofishing derive used in work is simulated to that used in the commercial fishing. The apparatus generates voltage ranged from 40 to 280 volts. Nine bearers of Poecilia latipinna sailfin molly fish in chromosomal analysis were divided into three treatments. The first were a control, the fishes of the second were exposed to 110 volts (10 seconds), and final groups were exposed to 110 volts (15 seconds). Mitotic index of the electrofishing with a control for each group decreased with increasing exposed time in somatic cell kidney tissue of Poecilia latipinna. The chromosome aberration analysis revealed a significant increase in the most frequent aberration per 150 metaphase in analyzed groups (1.33 in T1 groups, 39.33 in T2 groups) was chromosome break, fragment, range chromosome, Sticky chromosome mean, were higher in comparison to non exposed electrical shock fishing groups (control groups T1). At the same time, it showed a higher positive correlation of total chromosome aberration frequencies between T1 and T2 groups, while, all fishes died in T3 groups. According to our results, we represented the first record in Iraq.

Impact of electric fishing on egg survival of whitefish, Coregonus lavaretus

AbstractPrevious studies on the effects of electrofishing on fish eggs have reported widely varying results, ranging from gentle to adverse impacts on egg survival rates, and this may be attributable to inadequately standardised assessment methods. The impact of electrofishing on the survival of European whitefish, Coregonus lavaretus L., eggs was analysed in laboratory experiments and in a comparative field study. Different anode distances and time points post‐treatment were evaluated after artificial fertilisation with milt of untreated males, and survival rates were determined in the morula stage. In the laboratory, no significant difference in survival rates was found between various time points of stripping the gametes post‐electric shock. In the treatment group, significantly lower survival rates were detected in eggs (98.6%; SE = 0.20%) compared to the control group (99.6%; SE = 0.11%). Analysis of the egg survival rates in relation to effective voltage, rather than anode distance, revealed a significant trend of declining survival with increasing effective voltage. In field studies, eggs of electroshocked fish showed significantly lower survival (94.8%; SE = 1.03%) than untreated controls (98.7%; SE = 0.38%). Although electrofishing enhanced egg mortality, overall survival was noticeably high (&gt;90%), indicating a relatively small impact.

Fishes from Lake Yaxhá, Mayan Biosphere Reserve, Petén, Guatemala

The Mayan Biosphere Reserve is the largest protected area in Guatemala. Lake Yaxhá is located inside the core zone. Using electrofishing, seines and gillnets we assessed the fish richness and community in 2011. We collected 18 species distributed in seven families, with Cichlidae (seven species) and Poecilidae (five species) the most specious. We evaluated the effectiveness of electrofishing to sample the most important fish in the artisanal fishery in Petén, Petenia splendida, with September being the month with the highest capture per unit of effort. Lake Yaxhá assemblage was similar to the Usumacinta through a hierarchical cluster analysis, despite being located in the Mopan-Hondo basin. Lake Yaxhá is the only system in the area that does not have non-native fish species, emphasizing the importance of conservation of this lentic system in the Mayan Biosphere Reserve.

Effects of electro-fishing on galvano-taxis and carcass quality characteristics in sea bass (Dicentrarchus labrax)

The aim of this study was to investigate the effects of electro-fishing in sea water. We evaluated the feasibility of an electro-fishing system using numerical simulations for laboratory tanks and the open sea and performing a laboratory experiment. A non-homogeneous bi-dimensional electric-field model for marine water and fish based on discrete formulation of electro-magnetic field equations was developed using GAME (geometric approach for Maxwell equations) software. Voltage gradients inside the fish and close to the body were determined. Results showed that fish in the open sea and in groups had greater internal voltage differences than did fish in tanks and single fish. Sea bass (length:10 and 30 cm) were exposed in laboratory tanks to pulsed direct current (PDC), 25-125 Hz and duty cycle (5-40%). We measured the electro-taxis and tetanus thresholds after electrical exposure. It is significant that these values decreased with increasing the size of fish. No differences were found after electro-fishing on overall appearance, internal and external haemorrhage, standard freshness scoring techniques and carcass quality characteristics

Electrofishing and salmonid movement: reciprocal effects in two small montane streams

The effects of electrofishing on salmonid movement and of salmonid movement on electrofishing‐derived abundance estimates were studied in two streams in western Montana, U.S.A. Electrofishing increased emigration of salmonids from study reaches for 1 day, but not for succeeding days, whereas immigration to study reaches was unaffected. Movement of most emigrating fishes was downstream. On these small streams, electrofishing did not appear to cause fishes to flee during sampling. Numbers of salmonids migrating between mark and recapture runs were small relative to the fish abundance estimates in study reaches, usually much less than the 95% CL for those estimates, thus disregarding movements of marked fishes from the study reaches would have produced small positive biases in abundance estimates. Overall, for this suite of salmonid species in mid‐summer in these streams, the effects of electrofishing on fish movement and of fish movement on abundance estimates were minor.

Induced Mortality and Sublethal Injuries in Embryonic Brook Trout from Pulsed DC Electroshocking

Abstract Despite heightened concern for potential adverse effects of electrofishing on fish, little information is available on the effects of electrofishing on juvenile fish. The purpose of our study was to determine if electrofishing impairs the survival and development of embryonic brook trout Salvelinus fontinalis. Brook trout embryos, both uncovered and buried in an artificial redd, were electroshocked at 21 d postfertilization (pre-eyed). Uncovered embryos also were electroshocked at 37 d postfertilization (eyed). When electroshocked, pre-eyed embryos suffered greater embryo mortality (85%) and incidence of hatchling morphological anomalies (22%) than unshocked embryos (14% and 7%, respectively), whereas hatching times and hatchling weights were similar between groups. Emergence from electroshocked pre-eyed embryos also was significantly lower (23%) than from unshocked embryos (67%), and the mean time at which fish emerged was longer for shocked embryos (88 d) than for unshocked embryos (85 d). Surv...

Movements of Brown Trout in a Small Stream: Effects of Electrofishing and Consequences for Population Estimates

Abstract Much of the knowledge on salmonid ecology is based on electrofishing. Because there is little information on how electrofishing affects the subsequent behavior of fish, some of the salmonid data may be unreliable. Estimates of population sizes of stream fish based on mark–recapture or removal rely to a large extent on electrofishing as well. The population estimates obtained can be affected by high rates of movement suggested among stream-dwelling fish, regardless of whether the movements are natural or sampling induced. The amount of movement before and after electrofishing a closed population of brown trout Salmo trutta was determined by trapping in a small stream during 1994–1996. To assess the influence of movements on mark–recapture estimates and evaluate obtained estimates in relation to removal estimates, four different estimates (removal in summer, removal in autumn, conventional mark–recapture, and mark–recapture considering fish movements) were made for the closed brown trout population...

Reduction in Growth due to Electrofishing and Tagging May Change Interannual Movement Behavior of Stream Salmonids: Evidence from Arctic Grayling in an Interior Alaskan Stream

I show that the growth rate of Arctic grayling Thymallus arcticus is reduced by electrofishing and tagging (Floy FD-67 internal anchor tags) and present evidence that this reduction may alter interannual movement behavior. I demonstrate the reduction in growth by comparing length at age and annual growth of fish that either were or were not electrofished and tagged 1 year previously. For six of the seven ages compared (ages 3–9), the mean length of electrofished and tagged fish was reduced; in four cases the reduction was significant (P < 0.05 or P < 0.001). Annual growth of electrofished and tagged fish was also significantly less than that of untagged fish (P < 0.0001), with a median reduction of 18%. These reductions in growth may change a fish's movement behavior because fish that move upstream grow more quickly than fish that stay put or move downstream. If differences in growth are responsible for differences in movement, the effects of electrofishing and tagging are large enough to turn a fish destined to move upstream into one that stays put or moves downstream.

Management Briefs: Field Evaluations of 230-V AC Electrofishing on Mortality and Growth of Warmwater and Coolwater Fish

Abstract Effects of electrofishing on mortality of eight species of fish and on the growth of two species of fish were evaluated under field conditions. The electrofishing gear had an output of 230-V, three-phase AC, and 2–7 A. Captured fish held in live-cages or a pond experienced little or no mortality over 1–40 d. Tag recapture data for largemouth bass and walleyes indicate survival and growth after 1–2 years were no different for fish captured by electrofishing than for fish captured by trap nets or angling. I conclude that 230-V AC electrofishing can be a practical method to capture many warmwater and coolwater species for mark-recapture studies in lakes with alkalinities of 26-144 mg/L (conductivities of 66–520 μS/cm). Output amperage should be regulated so that fish are only briefly stunned.

Effects of Direct Current Electrofishing on the Mottled Sculpin

Abstract We examined the effects of electrofishing on the survival of mottled sculpin Cottus bairdi in two experiments. Three tanks each were filled with mottled sculpin collected by electrofishing (treatment) and by kick-seining (control). We maintained these tanks for at least 30 d and recorded all deaths. Patterns of survival were not significantly different among tanks in either of the experiments. In addition, there were no significant differences between pooled data sets (all control tanks versus all treatment tanks) within each experiment. Failure to demonstrate a treatment effect in either experiment suggests that electrofishing does not adversely affect the short-term survival of mottled sculpin. Although sample sizes were insufficient for statistical analysis, a similar result was obtained for several other species of stream fishes. To test the effects of multiple electrofishing exposures, we conducted another experiment in four artificial stream sections. Treatment mottled sculpin were shocked,...

Estimation of the Age-frequency Distribution of Stream-dwelling Trout by Underwater Observation

In Idaho, as in much of western North America, a large number of flowing waters exist where the effectiveness of electrofishing is reduced because of combinations of factors such as deep water, high clarity, abundant macrophytes, and particularly high or low conductivity. Under such circumstances, underwater observation is an effective census technique and may be useful in gathering other types of data. As part of a program to evaluate and maximize the utility of underwater observation in western streams, this study was designed to test whether an underwater observer with some prior knowledge of the age and size distribution of a trout population could successfully estimate the age-frequency distribution for that population. The study was performed in small streams which could be observed from bank to bank by a single diver. Data gathered from observations were compared with those obtained by electrofishing the same populations of fish.

Physiological Effects of Electrofishing on Largemouth Bass

Abstract Blood and tissue samples of adult largemouth bass (Micropterus salmoides) were taken from control fish and from fish that were electroshocked and allowed recovery times of 0, 1, 3, 5.5, and 19 h. Shocking had no significant effect (P > 0.05) on hemoglobin, hematocrit, plasma protein, or percentage water content of tissue. No sexual differences in these factors were noted. Blood lactate increased significantly (P <0.01) l h after electroshocking, returned to pre-shocked levels within a 3-h period, and then continued to decline.

The effects of electrofishing on the invertebrates of a Lake District stream.

The experiments were performed in Dale Park Beck, a stony stream in the English Lake District. Two operators electrofished the sampling area (length 20 m in April and July 1970, and 40 m in May 1971) three times (runs 1, 2, 3) in each experiment.Electrofishing caused a marked increase in the number of invertebrates drifting out of the sampling area, and nearly all taxa taken in the bottom samples were also found in the drift samples. The fish shocker was chiefly responsible for the increased drifting of Plecoptera, Ephemeroptera and Gammarus pulex, and these taxa were dislodged from the substratum more easily than Trichoptera, Coleoptera, Diptera and Polycelis felina. The increased drifting of the latter taxa was chiefly due to the disturbance of the substratum by the two operators.Most of the invertebrates drifting from the upstream end of the experimental section returned to the bottom within the sampling area. The invertebrate drift out of the sampling area came chiefly from the downstream end of the section, and was equivalent to a loss of only 5% from the total benthos in the sampling area (losses varied between <1 and 13% for individual taxa).