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Fishing sustainably is a fundamental problem in tropical regions where diverse fisheries and scarce fisheries information challenges efforts to make reliable estimates and associated policies. To improve evaluations and decisions, we compared the predictions of six surplus production models calibrated using various permutations of fisheries‐dependent data with a benchmark model. The benchmark model was built from fisheries‐independent estimates of r and K, tested against rates of change in Kenyan reef fisheries and found to be accurate. Comparisons with the benchmark model were made with fisheries‐dependent equilibrium and non‐equilibrium models, fixing or not fixing r and K, pooled versus site averaged solutions, and rising, falling, and pooled fishing effort over time. Evaluations indicate high variability in MMSY predictions and notable overestimates of MMSY (~75%) and effort (~210%) for Fox and Schaefer equilibrium models. Non‐equilibrium models had high failure rates (~25%) but successful fits performed better and indicated smaller overestimates (16%) for site‐level evaluations. The Pella–Tomlinson model was most accurate (MMSY = 5.6 ± 0.60 (SD) tonnes/km2/year) and best‐fit r‐K relationships also aligned well with ecoregional data on K and short‐term yields. Future efforts are advised to pool site data, use conservative recruitment values (z = 0.8), and collect data across times of both rising and falling effort. Recommended methods and subsequent adjustments of the benchmark model should improve local and ecoregional scale MMSYs. The benchmark model was calibrated to estimate MMSY in fished seascapes, but to conserve species with slower life histories, we suggest modifications to limit MMSYs to between 1.8 and 3.2 tonnes/km2/year. 相似文献
84.
Tim R. McClanahan Nyawira A. Muthiga Joseph Maina Albogast T. Kamukuru Saleh A.S. Yahya 《水产资源保护:海洋与淡水生态系统》2009,19(7):758-771
- 1. Surveys of coral reefs in northern Tanzania were conducted in 2004/5 with the aim of comparing them over an～8‐year period during a time of increased efforts at fisheries management and the 1998 El Niño Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD) coral mortality event that caused 45% mortality in northern Tanzania and much of the Indian Ocean.
- 2. Changes associated with both management, its absence, and the ENSO were found but changes were generally small and ecological measures indicated stability or improvements over this period, particularly when compared with reports from much of the northern Indian Ocean.
- 3. Fisheries management in two areas increased the biomass of fish and benthic communities. A small fisheries closure (0.3 km2) displayed little change in the coral community but ecological conditions declined as measured by sea urchins and fish abundances. This change may be associated with its small size because similar changes were not measured in the large closure (28 km2).
- 4. The few sites without any increased management were still degraded and one site had experienced a population explosion of a pest sea urchin, Echinometra mathaei.
- 5. The lack of significant changes across this disturbance indicates that these reefs are moderately resilient to climate change and, therefore, a high priority for future conservation actions.
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Ayana E Johnson Joshua E Cinner Marah J Hardt Jennifer Jacquet Tim R McClanahan James N Sanchirico 《Fish and Fisheries》2013,14(3):281-292
Artisanal coral reef fisheries provide food and employment to hundreds of millions of people in developing countries, making their sustainability a high priority. However, many of these fisheries are degraded and not yielding their maximum socioeconomic returns. We present a literature review that evaluates foci and trends in research effort on coral reef fisheries. We describe the types of data and categories of management recommendations presented in the 464 peer‐reviewed articles returned. Identified trends include a decline in articles reporting time‐series data, fish catch biomass and catch‐per‐unit effort, and an increase in articles containing bycatch and stakeholder interview data. Management implications were discussed in 80% of articles, with increasing frequency over time, but only 22% of articles made management recommendations based on the research presented in the article, as opposed to more general recommendations. Key future research priorities, which we deem underrepresented in the literature at present, are: (i) effectiveness of management approaches, (ii) ecological thresholds, trade‐offs and sustainable levels of extraction, (iii) effects of climate change, (iv) food security, (v) the role of aquaculture, (vi) access to and control of fishery resources, (vii) relationships between economic development and fishery exploitation, (viii) alternative livelihoods and (ix) integration of ecological and socioeconomic research. 相似文献
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SL Smith DM West PR Wilson GW de Lisle MG Collett C Heuer 《New Zealand veterinary journal》2013,61(5):240-243
Abstract AIM: To determine whether viable Mycobacterium avium subsp. paratuberculosis (Map) is present in skeletal muscle and blood in ewes with and without Johne's disease confirmed histologically. METHODS: A total of 51 mixed-aged ewes in poor body condition from a farm with a history of clinical Johne's disease were culled and examined at necropsy. BACTEC radiometric culture was performed on samples of skeletal muscle from the biceps femoris, mononuclear cells in peripheral blood (hereafter referred to as blood), and ileum. Histological sections and Ziehl-Neelsen (ZN)-stained impression smears of terminal ileum and mesenteric lymph nodes were examined. Ewes were defined as having confirmed Johne's disease if there was histopathological evidence typical of the disease within the ileum and adjacent lymph nodes. RESULTS: Eighteen of 21 (86%) ewes with confirmed clinical Johne's disease were culture-positive for Map from sites peripheral to the alimentary tract, comprising 15 from skeletal muscle and 13 from blood. Five of 30 (17%) ewes that did not have Johne's disease were culture-positive, with four from skeletal muscle and one from blood. The likelihood that ewes with confirmed Johne's disease had systemic Map infection compared with ewes without was determined as OR=30 (95% CI=6.3–142.0; p<0.001). CONCLUSION: The prevalence of Map infection of skeletal muscle and blood in ewes with confirmed Johne's disease was 71% and 62% respectively, and in unaffected ewes was 13% for muscle and 3% for blood. CLINICAL RELEVANCE: Skeletal muscle and blood are potential sources of exposure of humans to Map, and the risk appears higher from sheep with Johne's disease. 相似文献
88.
Abstract Extract Most perennial ryegrass (Lolium perenne) plants in pastures in New Zealand contain a naturally occurring fungal endophyte, Neotyphodium lolii. Endophyte-infected perennial ryegrass produces alkaloids that vary in concentration during the year. Some alkaloids enhance the persistence and productivity of ryegrass pastures by protecting them against insect attack. However, when other alkaloids are consumed they can reduce animal performance and lead to health problems. The alkaloid lolitrem B, for example, causes the neuromuscular disorder ryegrass staggers (Fletcher et al 1999). Clinical symptoms of ryegrass staggers in animals range from slight muscular tremors through to staggering and complete collapse. Severely affected animals create management problems and are prone to accidental death. Outbreaks occur sporadically, particularly in summer and autumn and affect sheep, cattle, deer, horses, llamas (Lama glama) and alpaca (Lama pacos). Lolitrem B appears to be a stable compound, which tends to be concentrated in the leaf sheath at the base of the ryegrass plant and in the seed-heads (di Menna et al 1992; Keogh et al 1996). Hay made from endophyte-infected perennial ryegrass contains large numbers of seed-heads and lolitrem B concentrations can be high, especially if it is made in late summer or autumn and, consequently, animals fed such hay are at risk of developing ryegrass staggers. 相似文献
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