Effects Of Fish Removal Research Articles

Effect of fish removal on the abundance and size structure of the sea urchin Diadema antillarum: A field experiment

Three decades after its population collapse, the sea urchin Diadema antillarum has yet to return to pre-mortality densities in most Caribbean localities. Circumstantial evidence suggests high post-settlement mortality due to predation as a potential mechanism to explain the lack of, or the slow recovery of this sea urchin. In this study we experimentally reduced the densities of two reef fish, Thalassoma bifasciatum and Halichoeres bivittatus, at one site for one year and measured the effect of their removal in the abundances and size structures of D. antillarum in relation to that of a comparable control site. We hypothesized a significant increase in urchin abundance and a reduction in mean test diameter at the experimental site with respect to the control site after the reduction in fish abundance. Overall, the density of D. antillarum did not vary significantly between control and experimental sites for the different census periods. Fish removal had a significant effect on the size structure of D. antillarum and in the mean density of the medium size classes. Results suggest that removal of these two labrids can significantly increase the relative abundance of medium-sized sea urchins and modify its population structure. Efforts to recover D. antillarum populations would be strengthened if densities of T. bifasciatum and H. bivittatus remain low.

Effects of Rotenone on Columbia Spotted Frogs Rana luteiventris during Field Applications in Lentic Habitats of Southwestern Montana

AbstractFisheries managers are restoring native populations by removing nonnative fishes worldwide. Increasingly, the piscicide rotenone is used to accomplish this. Fish introductions and removals change the aquatic environment, and it is important to consider the impacts of these actions on nontarget species, including amphibians. Laboratory experiments have shown that rotenone can negatively affect tadpoles. We therefore assessed the effects of rotenone used on two wild amphibian populations. The commercial piscicide formulation CFT Legumine (5% rotenone) was applied at 1 mg/L (50 μg/L rotenone) to a lake containing nonnative trout in Yellowstone National Park (YNP) in 2006 and two fishless wetlands on private lands in southwestern Montana in 2008. Amphibian surveys were conducted immediately prior to and after the rotenone treatments to obtain tadpole population estimates. Follow‐up surveys were conducted 1 year posttreatment to estimate tadpole recovery. In YNP, additional surveys were conducted 2 and 3 years postapplication to observe longer‐term effects of fish removal and the subsequent introduction of native fish. Within 24 h following application of rotenone, there was 100% mortality in gill‐breathing tadpoles, but nongill‐breathing metamorphs, juveniles, and adults were apparently unaffected. In the years following, tadpoles repopulated all waters and population levels were similar to, or, in the case of YNP because of concurrent fish removal, higher than pretreatment levels. In YNP, tadpole abundance and distribution decreased after westslope cutthroat trout Oncorhynchus clarkii lewisi were stocked in the treated lake.Received October 22, 2011; accepted May 4, 2012

Removal of nonnative fish results in population expansion of a declining amphibian (mountain yellow-legged frog, Rana muscosa)

The mountain yellow-legged frog ( Rana muscosa) was once a common inhabitant of the Sierra Nevada (California, USA), but has declined precipitously during the past century due in part to the introduction of nonnative fish into naturally fishless habitats. The objectives of the current study were to describe (1) the effect of fish removal from three lakes (located in two watersheds) on the small, remnant R. muscosa populations inhabiting those lakes, and (2) the initial development of metapopulation structure in each watershed as R. muscosa from expanding populations in fish-removal lakes dispersed to adjacent habitats. At all three fish-removal lakes, R. muscosa population densities increased significantly following the removal of predatory fish. The magnitude of these increases was significantly greater than that observed over the same time period in R. muscosa populations inhabiting control lakes that remained in their natural fishless condition. Following these population increases, R. muscosa dispersed to adjacent suitable (but unoccupied) sites, moving between 200 and 900 m along streams or across dry land. Together, these results suggest that large-scale removal of introduced fish could result in at least partial reversal of the decline of R. muscosa. Continued monitoring of R. muscosa at the fish-removal sites will be necessary to determine whether the positive effects of fish eradication are sustained over the long-term, especially in light of the increasingly important role played by an emerging infectious disease (chytridiomycosis, caused by Batrachochytrium dendrobatidis) in influencing R. muscosa populations.

Effects of fish removal on cyanobacteria and their toxicity in Lake Tuusulanjärvi, Southern Finland

Effects of fish removal on cyanobacteria and their toxicity in Lake Tuusulanjärvi, Southern Finland

Eutrophication and its control by biomanipulation: an enclosure experiment

Biomanipulation experiments were carried out in small enclosures in a small, shallow eutrophic lake in eastern England. The effects of fish removal on water quality and planktonic communities were examined in relation to nutrients and macrophytes. Exclusion of fish resulted in enhanced densities of the large-bodied Daphnia hyalina which, in turn, led to improvements in water quality. The provision of refuges from fish predation also enhanced Daphnia populations enough to suggest this strategy as feasible for the restoration of this lake. The development of a mysid population in enclosures without fish indicated that some indirect effects might occur if fish are completely removed.

Effects of Fish Removal on the Limnetic Ecosystem of a Eutrophic Lake

The effects of fish elimination in the eutrophic Lake Haugatjern, Sør-Trøndelag County, Norway, were studied during 1979–84. Total elimination of the fish populations by rotenone in late 1980 resulted in a fourfold decrease in the algal biomass. The species composition changed from a dominance by the large-sized Anabaena flos-aquae and Staurastrum luetkemuelleri to smaller, fast-growing species and gelatinous green algae. The total zooplankton biomass remained at the same level in all years, but while the rotifers almost disappeared after the rotenone treatment, the daphnids increased their share of the biomass from 49–63% during 1979–80 to 74–90% during 1982–84. The mean individual size of the adult daphnids increased in the same period from 1.3 to 1.8 mm. A 30% drop in the total phosphorus concentration in the lake after the biomanipulation was explained by increased sedimentation of zooplankton and reduced phosphorus release from the epilimnetic sediments because of the lowered pH. The fish elimination also resulted in a lower yield of biomass per unit of phosphorus in the lake.

Effects of fish removal from a small lake

Effects of fish removal from a small lake

Effect of Fish Removal on the Growth and Condition of White Shrimp in Brackish Ponds1

ABSTRACTThe effect of fish removal on the growth and condition of juvenile white shrimp (Penaeus setiferus) was examined using a 0.5 and 1.0 ha pond near West Galveston Bay, Texas. Prior to stocking, the 1.0 ha pond was treated with a rotenone compound (Chem Fish Collector) at a rate of 1.0 ppm to remove fish. Those species removed were Brevoortia patronus, Myrophis punctatus, Cyprinodon variegatus, Fundulus grandis, Poecilia latipinna, Leiostomus xanthurus, Mugil cephalus, and Menidia beryllina. These species were abundant in the 0.5 ha pond. Juvenile white shrimp were stocked in both ponds at a rate of 50,000 per ha and fed a supplemental pelleted ration 3 days a week at a rate of 10% of their estimated total weight.After 77 days, shrimp in the treated pond averaged 12.3 mm longer and 4.0 g heavier than those in the pond with fish, and seine samples indicated that shrimp abundance had noticeably declined in the pond with fish. It was concluded that fish not only prey on shrimp, thus reducing their numbers, but also compete with them for supplemental and natural feeds, thus depressing their growth rate. Condition of shrimp in the treated pond was significantly better than in the untreated pond throughout the duration of the experiment, but this probably resulted because the seed stock were taken from different bay populations. In both ponds, the condition of the shrimp declined drastically during the first 8 days after stocking, but then gradually improved throughout the remainder of the experiment. The length‐weight relationship of shrimp in each pond is also presented. A comparison of these relationships confirmed that shrimp in the treated pond were in better condition throughout their entire size range than those in the pond with fish, but again, the difference could be the result of different populations of seed stock.

The Effects of Fish Removal and Other Factors Upon Remaining Fish Populations at Lake Trafford, Florida

The Effects of Fish Removal and Other Factors Upon Remaining Fish Populations at Lake Trafford, Florida