1,364,046 research outputs found
POTENTIAL IMPACTS OF THE ASIAN CLIMBING PERCH ON QUEENSLAND
No full textRisk of establishment of the freshwater climbing perch (Anabas testudineus) in mainland Queensland from the Torres Strait is high. The species is dispersed through human assistance and/or attributes that assist its own spread. The species has the potential to out-compete native freshwater and estuarine species, and has sharp well-developed gill plates and spines that may choke and kill predatory species like barramundi if swallowed. The presence of climbing perch would severely impact Queensland’s inshore and freshwater fisheries, both commercial and recreational. The net present value of expected lost fishing activity due to build-up of the climbing perch is $48.5 million when the probability of introduction is 20 per cent. Analysis of potential spending on an entry prevention strategy for the climbing perch can be justified, with a benefit cost ratio of 150 to 1.Invasive species, impact, risk, Resource /Energy Economics and Policy, Risk and Uncertainty,
The invasion of an introduced predator, Nile perch (Lates niloticus, L.) in Lake Victoria (East Africa): chronology and causes
No full textNile perch, a large predatory fish, was introduced into Lake Victoria in 1954. The upsurge of Nile perch in Lake Victoria was first observed in the Nyanza Gulf, Kenya, in 1979. In Ugandan waters this occurred 2¿3 years later and in the Tanzanian Mwanza Gulf 4¿5 years later. At the beginning of the upsurge in the Mwanza Gulf in 1983/1984 only sub-adult and adult fishes were found. The first juveniles appeared in 1985, suggesting that the initial increase of Nile perch was mainly caused by migration of sub-adults and adults. Shortly after the onset of trawl fishery in the area in 1973, haplochromines in the Mwanza Gulf started to decline. The final disappearance of the haplochromines, in 1987, only occurred after the Nile perch boom, and despite the abandoning of the haplochromine fishery in 1986. We hypothesize that the decline of haplochromines decreased predation on and competition with juvenile Nile perch and then facilitated survival of these juveniles. Consequently the immigration of sub-adult and adult Nile perch in an area may have paved the way for successful recruitment. Over-exploitation of haplochromine cichlids in the 1970s in the Nyanza Gulf, where the Nile perch upsurge was first observed, may have played a similar role
Cryopreservation of Pike Perch Sperm in Hatchery Conditions
No full textExperiments were carried out on pike perch (Sander lucioperca L.) to find a method for stripping
sperm without contamination by urine, to determine sperm concentration, and to fertilize large
batches of eggs with cryopreserved sperm. Induced spawning technology for pike perch, an
important predator fish species in Hungarian and central-eastern European pond aquaculture,
has been developed only recently. Sperm cryopreservation can be an important tool for several
reasons including the simplification of hatchery work and long-term preservation of genomes of
males with high genetic value. In the present study, sperm was stripped without urine contamination,
improving sperm quality, and large amounts of eggs were fertilized using 0.25 ml sperm,
resulting in hatching percentages of 55±3% for 30-g batches of eggs and 87% for a 50-g batch
White Perch Expansion and Life History Within a Southern Reservoir
No full textConcern has been raised regarding the effects of invasive fishes, among them white perch (Morone americana), in a variety of freshwater systems. Previous research on white perch as an invasive species has examined landlocked white perch in ponds, lakes and reservoirs throughout much of its geographic range. However, research has been lacking regarding the role of invasive white perch in southern reservoirs. A long-term data set of the Jordan Lake fish community indexed via gill nets was evaluated to assess the expansion of white perch in Jordan Lake, as well as concurrent declines in other fishes found in Jordan Lake from 1987 through 1998. White perch catch rates increased from zero fish per net night in 1987 to 16.1 fish per net night in 1994, surpassing catch rates for all other fish captured in gill nets. White perch were found to live to age 7 in Jordan Lake where they shift food habits seasonally from zooplankton and diptera larvae in the spring to young shad in the fall. Relative weights and mean calculated total lengths at annulus formation suggest that the Jordan Lake white perch population is in good condition, comparable to other landlocked white perch populations in North Carolina and surpassing white perch populations found in their native estuarine environs throughout the eastern seaboard. Young white perch were found to prefer cover-free primary points featuring hard sand and clay substrates, minimizing the likelihood that Jordan Lake white perch will impact centrarchids as has been suggested by research in other freshwater systems outside of the southeastern United States
Food competition and its relation to aquaculture in Perca fluviatilis
No full textIn this thesis, explanations for, and predictors of, the large growth heterogeneity, in juvenile perch in aquaculture and natural environments, were studied. A large variation between individuals in competitive ability, estimated as feeding success or growth, was found. Relative feeding success (in aquaria) and growth rates (in tanks) of individuals were consistent over time within environments but not positively correlated between them. It was indicated that individual feeding success was negatively correlated between environments. Individuals may be differently prone to be successful in specific environments due to variations in innate characteristics, but this has not been tested. Predation risk decreased boldness (risk proneness) but did not affect food intake at the individual level. Better competitors were also bolder. Feeding success was positively correlated to growth rate within aquaria, but not between environments (aquaria vs. tanks). Group composition affected individual boldness but not food intake. Strong social hierarchies were not found, but aggressive behaviour was observed in one study. Thus, a large variation in boldness and competitive ability was found, and this variation may be of importance for the large variation in growth. There was a seasonal variation in growth. This knowledge is important for optimising feed management, thereby maximising growth and economics and minimising environmental impact of future perch farms. The consistency in the differences in individual growth rate indicates that perch have a large potential for successful breeding programs. Boldness and competitive success in aquaria experiments can not be used as indicators of individual growth potential. High light intensities were found to stress the perch, indicated by an increased swimming activity. Tank wall colour did not seem to affect behaviour or growth, and no colour was selected over others
Growth, mortality and recruitment of Nile perch Lates niloticus (L. Centropomidae) in the Nyanza Gulf of Lake Victoria: an evaluation update
No full textA reassessment of the estimates of growth, mortality and recruitment patterns of Nile Perch, Lates niloticus was made based on data from commercial landings collected during the Catch Assessment Survey Programme. Two sets of length frequency data, one each from beach seining and hook and line fisheries, were analyzed. Values of L8 = 169 and 230 (cm TL) and K= 0.18 yr-1 and 0.195 yr-1 were obtained. The total mortality estimates from the catch curve analysis were Z = 0.72 yr-1 and 0.94 yr-1, respectively, with a natural mortality M of about 0.35 for a mean environmental temperature of 27oC. The highest peak for recruitment was in November, December and January with a minor one in June, indicating recruitment of two cohorts per year. These results are discussed and compared to previously available information on L. niloticus in Lake Victoria.Growth, Mortality, Recruitment, Kenya, Victoria L., Nyanza Gulf, Lates niloticus
Movements of tagged yellow perch, Perca flavescens (Mitchell), in Indiana waters of Lake Michigan during 1980 and 1981
No full textDuring 1980 and 1981 respectively, 2425 and 4028 yellow perch 150-359 mm were Floy-tagged from June through August at four sites in Indiana waters of Lake Michigan. Most of the 6453 perch were tagged from mid-June to early August and almost 90% were less than 210 mm.An overall recapture rate of 3.2% (204 fish) was obtained by April 1, 1982. Site recapture rates were positively related to the numbers of fish tagged. Slightly over 92% of all fish were tagged at sites M and K and 94.5% of all recaptures originated from these two sites. Second season recaptures accounted for 25.5% of all recaptures. Peak recapture rates occurred in July. Sources of recaptures were 67.6% from sport fishermen, 25.5% from commercial fishermen, and 6.9% from Indiana Department of Natural Resources, Ball State University trawl catches and other sources.Most recaptured perch were in the 150-229 mm length interval, but an apparent size selection by both commercial and sport gear existed towards 180-229 mm perch. The recapture of large numbers of 150-159 mm fish indicated survival of small perch was not an important factor influencing size selection. Information on sizes of fish recaptured by sex and age was insufficient for evaluation.Although straight line movements of up to 166 km occurred, most fish remained near the original tagging sites. Distances traveled were similar for fish from all tagging sites in 1980, 1981 and for second season recaptures. Over 76% of all fish were recaptured in Indiana waters and about 86% traveled less than 32.0 km from the original tagging sites. The majority (64%) of fish leaving Indiana waters were captured nearby at New Buffalo and Union Pier, Michigan. About 68% of all recaptures were received within 60 days of release. Even though considerable variability was evident in the distances traveled with time, no seasonal trends were observed for perch of various sizes.Simple regression analysis of data for combined years revealed only 27% of all variation in distance traveled by perch was accounted for by the time at large (days) prior to recapture. Multiple regression analysis revealed the time at large was more important than fish length in relation to distance traveled, accounting for 27.3% and 0.2% of the explained variability, respectively. Data including second season recaptures more accurately represented these relationships and indicated these variables were poorly related to distance traveled. Examination of residuals showed a dramatic and statistically undesirable increase in unexplained variability was associated with far ranging fish. Other factors should be considered in future multiple regression analyses.Indiana yellow perch stocks appear to be fairly discrete entities. The majority of fish tended to remain periods of at least one year.Thesis (M.S.
Habitat selection and indirect interactions in fish ommunities
No full textTo increase the understanding of freshwater lake ecosystems, I have studied the habitat selection of perch (Perca fluviatilis L.), roach (Rutilus rutilus (L.)), and vendace (Coregonus albula (L.)). These fish species use the pelagic and the littoral-benthic habitats in lakes to different extents. Perch and roach are omnivorous, and perch become piscivorous at larger sizes. Vendace is a pelagic species specialized in eating zooplankton. Vendace was expected to affect biotic interactions and habitat use of roach and perch, both directly and indirectly.
I used monitoring data to examine how species distribution patterns, as well as population structures, depended on species composition. In a predation experiment, I studied the relative predation sensitivity as well as evasive behaviours of roach and vendace, with piscivorous perch used as predators. In foraging experiments in aquaria, I studied foraging efficiencies and swimming performances of roach and vendace eating zooplankton in different temperature and light treatments. I then applied metabolic models for roach and vendace, respectively, to compare their net energy gain in different abiotic conditions.
Roach used the pelagic habitat less, and the biomass of roach was lower in lakes with vendace. Results did not support the prediction that perch populations would benefit from the presence of vendace. However, results indicated that a release of competition for small perch may be mediated by vendace, through changed habitat use of roach, increasing the possibilities for predation. Roach and vendace were similar in their sensitivity to predation, indicating that energy gain can explain their habitat use. Foraging efficiencies did not explain the habitat use of roach and vendace in the field. However, the net energy gain in different abiotic conditions, could explain observed patterns of their habitat use in lakes.
This thesis shows how the trade-off between mortality and net energy gain is manifested in habitat use. Including habitat selection in ecological studies may increase our understanding of biotic interactions. Metabolic costs as well as foraging abilities in different abiotic conditions are important for explaining the habitat use of species. Such knowledge can make it possible to forecast how interacting fish species may be affected by environmental change
Food habits of the yellow perch in Indiana waters of Lake Michigan near Michigan City, Indiana, in 1971-72
No full textYellow perch, Perca flavescens (Mitchill), were collected for food habit determination from a transect in Indiana waters of Lake Michigan near Michigan City, Indiana between June and October in 1971 and June and September in 1972.The most important food items utilized on a mean annual basis were: unidentifiable organic material (UOM), alewife eggs, Pontoporeia affinis, fish (primarily alewife), insects (primarily chironomid larvae and pupae), and Eurycercus lamellatus. E. lamellatus, alewife eggs and UOM dominated 1971 stomach contents with P. affinis more important than E. lamellatus in 1972.Monthly stomach contents revealed heavy consumption of alewife eggs when available during the alewife spawning period, but these were replaced by P. affinis and fish (alewife) especially after July in both years.Differences between sexes of yellow perch captured by day and by night were minor and inconsistent.Differences between selected size groups (100-175, 176-225, 226-275 mm) manifested themselves in greater use of larger food items such as P. affinis and fish with larger length groups and as the summer progressed. The mean volumes of alewife eggs consumed, the most important food of yellow perch in this study, decreased significantly within each month both years as length of the yellow perch increased. In the large length groups, greater use of larger food items was made, but only fishes as a food item showed a signigicant difference between the two larger length groups.Thesis (M.S.
The translocation of golden perch, Murray cod and Australian bass, into and within Western Australia, for the purposes of recreational stocking, domestic stocking and commercial and non-commercial aquaculture
No full textThis discussion paper has been prepared to provide information to assist in assessment of the possible impact of the translocation of golden perch (Macquaria ambigua), Murray cod (Maccullochella peelii peelii) and Australian bass (Macquaria novemaculeata) into and within Western Australia, for the purposes of recreational stocking, domestic stocking, commercial and non-commercial aquaculture.
In assessing the translocation of any aquatic species, economic and social benefits must be balanced with biological and environmental risks
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