978 resultados para Tuna fishing
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Change in individual growth rate and its link to gill-net fishing in two sympatric whitefish species
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Size-selective fishing is expected to affect traits such as individual growth rate, but the relationship between the fishery-linked selection differentials and the corresponding phenotypic changes is not well understood. We analysed a 25-year monitoring survey of sympatric populations of the two Alpine whitefish Coregonus albellus and C. fatioi. We determined the fishing-induced selection differentials on growth rates, the actual change of growth rates over time, and potential indicators of reproductive strategies that may change over time. We found marked declines in adult growth rate and significant selection differentials that may partly explain the observed declines. However, when comparing the two sympatric species, the selection differentials on adult growth were stronger in C. albellus while the decline in adult growth rate seemed more pronounced in C. fatioi. Moreover, the selection differential on juvenile growth was significant in C. albellus but not in C. fatioi, while a significant reduction in juvenile growth over the last 25 years was only found in C. fatioi. Our results suggest that size-selective fishing affects the genetics for individual growth in these whitefish, and that the link between selection differentials and phenotypic changes is influenced by species-specific factors.
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Laboratory-reared Lutzomyia longipalpis (Lutz and Neiva 1912) was tested with extracts of two ichthyotoxic plants, known as timbós, used as fishing poison in the Amazon. Phlebotomines, L. longipalpis, and plants, Antonia ovata and Derris amazonica, were collected in the Raposa-Serra do Sol Indian Reserve, a focus of visceral leishmaniasis in the State of Roraima, Brazil. Extracts were prepared from dried leaves of A. ovata and roots of D. amazonica that were percolated in water, filtered and dried out at 50°C. The solid extract obtained was diluted in water at 150, 200 and 250 mg/ml. The solution was blotted in filter paper placed at the bottom of cylindric glass tubes containing sand flies. For each plant extract and dilution, two series of triplicates with 5 male and 5 female specimens of L. longipalpis were used. Mortality was recorded every 2 h during 72 h of exposure. At 72 h the mortality was as high as 80% for extracts of A. ovata (LD50 = 233 mg/ ml), and 100% for D. amazonica (LD50 = 212 mg/ ml) whereas in the control groups maximum mortality never surpassed 13%. Preliminary assays indicated that A. ovata and D. amazonica displayed significant insecticide effect against L. longipalpis.
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Patterns of parasite abundance and prevalence are thought to be influenced by several host characteristics such as size, sex, developmental stage, and seasonality. We examined two obligatory ectoparasites of the bat Noctilio leporinus (L.) (Chiroptera, Noctilionidae) to test whether prevalence and abundance of Noctiliostrebla aitkeni Wenzel and Paradyschiria fusca Speiser (Diptera, Streblidae) are influenced by the host characteristics. During this survey, 2110 flies were collected. The total abundance was 1150 N. aitkeni and 950 P. fusca. The prevalence of both species was shown to be superior to 75% and neither host size, sex, reproductive stage nor season influenced significantly the variation of the observed values. N. aitkeni were more abundant than P. fusca in all seasons except winter. Both flies showed a significant seasonal variation in terms of abundance but host biological characteristics (host size, sex, and reproductive stage) did not play a significant role as structuring factors of the batflies component community.
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This booklet is not a complete set of hunting laws. It contains basic information needed during the hunting, fishing and trapping seasons.
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Fishing Regulations and Bag Limits
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Managing fisheries resources to maintain healthy ecosystems is one of the main goals of the ecosystem approach to fisheries (EAF). While a number of international treaties call for the implementation of EAF, there are still gaps in the underlying methodology. One aspect that has received substantial scientific attention recently is fisheries-induced evolution (FIE). Increasing evidence indicates that intensive fishing has the potential to exert strong directional selection on life-history traits, behaviour, physiology, and morphology of exploited fish. Of particular concern is that reversing evolutionary responses to fishing can be much more difficult than reversing demographic or phenotypically plastic responses. Furthermore, like climate change, multiple agents cause FIE, with effects accumulating over time. Consequently, FIE may alter the utility derived from fish stocks, which in turn can modify the monetary value living aquatic resources provide to society. Quantifying and predicting the evolutionary effects of fishing is therefore important for both ecological and economic reasons. An important reason this is not happening is the lack of an appropriate assessment framework. We therefore describe the evolutionary impact assessment (EvoIA) as a structured approach for assessing the evolutionary consequences of fishing and evaluating the predicted evolutionary outcomes of alternative management options. EvoIA can contribute to EAF by clarifying how evolution may alter stock properties and ecological relations, support the precautionary approach to fisheries management by addressing a previously overlooked source of uncertainty and risk, and thus contribute to sustainable fisheries.
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Fishing Regulations for the state of Iowa
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This article challenges the notion of economic rationality as a criterion for explaining ethnic boundary maintenance. It offers an ethnographic analysis of inter-ethnic relations in the context of games (cockfights and game-fishing contests) in the island of Raiatea (French Polynesia). Although all players engage in the same basic gambling practices, money is differentially scaled and mobilized by the Tahitian and Chinese participants. Building on recent pragmatic approaches to rationality, it is shown that the players' rationalities differ not from the point of view of economic maximization, but only in so far as they participate in social relations at different scales.
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Under team production, those who monitor individual productivity areusually the only ones compensated with a residual that varies withthe performance of the team. This pattern is efficient, as is shownby the prevalence of conventional firms, except for small teams andwhen specialized monitoring is ineffective. Profit sharing in repeatedteam production induces all team members to take disciplinary actionagainst underperformers through switching and separation decisions,however. Such action provides effective self-enforcemnt when themarkets for team members are competitive, even for large teams usingspecialized monitoring. The traditional share system of fishing firmsshows that for this competition to provide powerful enough incentivesthe costs of switching teams and measuring team productivity must bebellow. Risk allocation may constrain the organizational designdefined by the use of a share system. It does not account for itsexistence, however.
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Experimental fishing and visual censuses were conducted at nine Posidonia oceanica sites off Minorca exposed to different levels of fishing intensity to assess the effects of recreational fishing on the species that dominate the catch. Total catch per unit effort (CPUE) was highly seasonal and a statistically significant interaction term existed between the season and the level of fishing intensity. CPUE decreased everywhere at the end of the fishing season (autumn), but such a reduction was more intense at those sites exposed to the highest level of fishing. Visual censuses confirmed that there was a lower abundance of vulnerable fish in autumn. Differences vanished in spring probably because fish reshuffled between the considered sites throughout the winter, when the level of fishing intensity was extremely low. Although the average total lengths of Serranus scriba and Diplodus annularis were unaffected by the level of fishing intensity, the average total length of Coris julis was smaller at the most heavily fished sites. In conclusion, recreational fishing has a relevant impact on most of the exploited species and some of the seasonality reported for the Posidonia oceanica fish assemblages might be caused by the seasonality of the fishery.
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This document lists Iowa lakes and provides their locations, major fish species found in the lake, information on shoreline access, boat rental, boat motor requirements, ramp type, camping availability and map availability. It also indicates if the lake has restrooms and playgrounds.