Reducing the capture of small fish, discarded fish, and bycatch is a primary concern of fisheries managers who propose to maintain high yields, species diversity, and ecosystem functions. Modified ...fishing gear is one of the primary ways to reduce by-catch and capture of smallfish. The outcomes of gear modification may depend on competition among fishers using other similar resources and other gears in the same fishing grounds and the subsequent adoption or abandonment of modified gears by fishers. We evaluated adoption of modified gear, catch size, catch per unit effort (CPUE), yield, and fisher incomes in a coral reef fishery in which a 3-cm escape gap was introduced into traditional traps. There were 26.1 (SD 4.9) fishers who used the experimental landing sites and 228(SD 15.7) fishers who used the control landing sites annually over 7 years. The size offish increased by 10.6% in the modified traps, but the catch of smaller fish increased by 11.2% among the other gears. There was no change in the overall CPUE, yields, or per area incomes; rather, yield benefits were redistributed in favor of the unmodified gears. For example, estimated incomes of fishers who adopted the modified traps remained unchanged but increased for net and spear fishers. Fishers using escape-gap traps had a high proportion of income from larger fish, which may have led to a perception of benefits, high status, and no abandonment of the modified traps. The commensal rather than competitive outcome may explain the continued use of escape-gap traps 3 years after their introduction. Trap fishers showed an interest in negotiating other management improvements, such as increased mesh sizes for nets, which could ultimately catalyze community-level decisions and restrictions that could increase their profits. La reducción de la captura de peces pequeños, peces descartados y la pesca incidental es una preocupación primordial para los administradores de las pesquerías que proponen mantener un rédito alto, la diversidad de especies y lasfunciones del ecosistema. El equipo de pesca modificado es una de las principales maneras para reducir la pesca incidental y la captura de peces pequeños. Los resultados de la modificación del equipo pueden depender de la competencia entre los pescadores que utilizan recursos similares y otros equipos en las mismas zonas de pesca y la adopción o abandono subsecuente del equipo modificado por parte de los pescadores. Evaluamos la adopción del equipo modificado, el tamaño de la captura, el esfuerzo de captura por unidad (CPUE), el rédito, y los ingresos de los pescadores en una pesquería de arrecife de coral en la que se introdujo un espacio de escape de 3 cm en las trampas tradicionales. Hubo 26.1 (SD 4.9) pescadores que utilizaron sitios experimentales de atraque y 228 (SD 15.7) pescadores que utilizaron los sitios control de atraque anualmente durante siete años. El tamaño de los peces incrementó en un 10.6% dentro de las trampas modificadas, pero la captura de peces pequeños incrementó 11.2% en los otros equipos. No hubo cambio en el CPUE general, el rédito, o en los ingresos por área; más bien, los beneficios del rédito fueron redistribuidos a favor de los equipos sin modificaciones. Por ejemplo, los ingresos estimados de los pescadores que adoptaron las trampas modificadas permanecieron sin cambios pero incrementaron para los pescadores que usan redes y lanzas. Los pescadores que utilizaron trampas con espacio de escape tuvieron una proporción más alta de ingresos por peces más grandes, lo que pudo haber resultado en una percepción de beneficios, estatus alto y ningún abandono de las trampas modificadas. El resultado comensal y no competitivo puede explicar el uso continuado de las trampas con espacio de escape tres años después de su introducción. Los pescadores que usan trampas mostraron un interés por negociar otras mejoras en el manejo, como un mayor tamaño malla para las redes, lo cual podría básicamente catalizar las decisiones y restricciones a nivel comunitario que podrían incrementar sus ganancias.
Abstract
A brief historical narrative of coral responses to climate change exposures is followed by a review of evidence. I trace the history of investigations and summarize the findings from 112 ...multiple-site field studies that examined environmental exposure variables and coral bleaching and mortality response relationships. A total of 59 environmental variables in six topic areas were studied of which excess thermal exposure was the most common topic and variable. Investigations were broadly classified into two categories; those focused on either excess thermal stress thresholds (TM) or on continuous variables (VM). The TM investigations considered a total of 28 variables, but only 1.7 ± 1.3 (SD) variables per publication, and only 11% completed a variable selection process that competed variables for fit or parsimony. The 65 VM publications considered 59 variables, more variables per publication (4.1 ± 4.3), and 43% of the studies followed a variable selection procedure. TM investigations received more citation and were most frequently used to identify future climate change impacts and sanctuaries. VM investigations often report excess heat threshold variables as weak single predictors of coral bleaching and mortality. Coral responses to exposure favors mechanisms of causation that are additive and interactive; specifically, the interactions between chronic and acute stresses within the geographic and habitat contexts of local environmental and coral genetic histories. Some of the potentially most important variables for predicting coral responses to exposure have seldom been studied or modeled. The implication is that the future status and health of coral reefs will be better than predicted by TMs. Moreover, impacts and sanctuaries are expected to be patchy and influenced by space, time, genetics, and taxa heterogeneity that will reflect a mix of avoidance, resistance, and recovery processes and their associated sanctuary locations.
Ecological baselines are disappearing and it is uncertain how marine reserves, here called fisheries closures, simulate pristine communities. We tested the influence of fisheries closure age, size ...and compliance on recovery of community biomass and life-history metrics towards a baseline. We used census data from 324 coral reefs, including 41 protected areas ranging between 1 and 45 years of age and 0.28 and 1430 km2, and 36 sites in a remote baseline, the Chagos Archipelago. Fish community-level life histories changed towards larger and later maturing fauna with increasing closure age, size and compliance. In high compliance closures, community biomass levelled at approximately 20 years and 10 km2 but was still only at approximately 30% of the baseline and community growth rates were projected to slowly decline for more than 100 years. In low compliance and young closures, biomass levelled at half the value and time as high compliance closures and life-history metrics were not predicted to reach the baseline. Biomass does not adequately reflect the long-time scales for full recovery of life-history characteristics, with implications for coral reef management.
The coral reefs of Papua New Guinea are among the most species diverse in the world, support an important artisanal fishery, but lack an effective national conservation programme. Increased ...commercialization, population growth, promotion of fisheries development projects, and the live reef food fish trade are expected to increase demand for the country's reef fish. This paper examines how socioeconomic factors affect the condition of the artisanal multi-species coral reef fishery in six sites in Papua New Guinea. Catch characteristics such as diversity, trophic level and body size by landing site were examined along a fishing pressure gradient. Both exogenous factors such as markets and endogenous factors such as fishing pressure were related to the condition of fish catch. In general, the trophic level and lengths of fish captured in Papua New Guinea were relatively high, but were reduced on reefs with high fishing effort near fish markets. Fisheries showed signs of depletion above c. 25 fishing trips per km2 per day and the proximity of markets was a better indicator of overfishing than human population size. A cross-scale approach to fisheries management is required in Papua New Guinea to coordinate decentralized local management, limit the intrusion of extractive enterprises, and develop policies that seek to minimize exogenous pressures on marine resources.
Western Indian Ocean coral communities McClanahan, T. R.; Ateweberhan, M.; Graham, N. A. J. ...
Marine ecology. Progress series,
05/2007, Letnik:
337
Journal Article
Recenzirano
Odprti dostop
A field study of coral bleaching and coral communities was undertaken spanning 8 countries and ~35° of latitude in 2005. This was combined with studies in southern Kenya and northeast Madagascar in ...1998 and Mauritius in 2004 to develop a synoptic analysis of coral community structure, bleaching response, susceptibility of the communities to bleaching, and the relative risk of extinctions in western Indian Ocean coral reefs. Cluster analysis identified 8 distinct coral communities among the 91 sites sampled, with 2 distinct communities in northern South Africa and central Mozambique, a third in the central atolls of the Maldives, and 5 less differentiated groups, in a swath from southern Kenya to Mauritius, including Tanzania, the granitic islands of the Seychelles, northeast Madagascar, and Réunion. MassivePorites,Pavona, andPocilloporadominated the central and northern Indian Ocean sites and, from historical records, replaced dominance byAcroporaandMontipora. From southern Kenya to Mauritius, coral communities were less disturbed, withAcroporaandMontiporadominating, and a mix of subdominants including branchingPorites,Fungia,Galaxea, massivePorites,Pocillopora, andSynarea. The survey identified an area from southernmost Kenya to Tanzania as having the least disturbed and highest diversity reefs, and as being a regional priority for management. Taxa vulnerable to future extinction based on their response to warm water, population density, and commonness include largely low-diversity genera with narrow environmental ranges, such asGyrosmilia interrupta,Plesiastrea versipora,Plerogyra sinuosa, andPhysogyra lichtensteini.
Hydrogen has been inferred to occur in enhanced concentrations within permanently shadowed regions and, hence, the coldest areas of the lunar poles. The Lunar Crater Observation and Sensing Satellite ...(LCROSS) mission was designed to detect hydrogen-bearing volatiles directly. Neutron flux measurements of the Moon's south polar region from the Lunar Exploration Neutron Detector (LEND) on the Lunar Reconnaissance Orbiter (LRO) spacecraft were used to select the optimal impact site for LCROSS. LEND data show several regions where the epithermal neutron flux from the surface is suppressed, which is indicative of enhanced hydrogen content. These regions are not spatially coincident with permanently shadowed regions of the Moon. The LCROSS impact site inside the Cabeus crater demonstrates the highest hydrogen concentration in the lunar south polar region, corresponding to an estimated content of 0.5 to 4.0% water ice by weight, depending on the thickness of any overlying dry regolith layer. The distribution of hydrogen across the region is consistent with buried water ice from cometary impacts, hydrogen implantation from the solar wind, and/or other as yet unknown sources.
•Recovery of Maldivian corals exhibits high spatial and taxonomic variability.•The emerging dominant taxa have stress tolerant and weedy life histories.•Some typically common taxa were still very ...rare.•The response to a thermal anomaly indicates taxa-specific adaptation.•Coral taxa most sensitive to anomalies displayed the greatest adaptive response.
This study provides a descriptive analysis of the North Male, Maldives seven years after the 1998 bleaching disturbance to determine the state of the coral community composition, the recruitment community, evidence for recovery, and adaptation to thermal stress. Overall, hard coral cover recovered at a rate commonly reported in the literature but with high spatial variability and shifts in taxonomic composition. Massive Porites, Pavona, Synarea, and Goniopora were unusually common in both the recruit and adult communities. Coral recruitment was low and some coral taxa, namely Tubipora, Seriatopora, and Stylophora, were rarer than expected. A study of the bleaching response to a thermal anomaly in 2005 indicated that some taxa, including Leptoria, Platygyra, Favites, Fungia, Hydnophora, and Galaxea astreata, bleached as predicted while others, including Acropora, Pocillopora, branching Porites, Montipora, Stylophora, and Alveopora, bleached less than predicted. This indicates variable-adaptation potentials among the taxa and considerable potential for ecological reorganization of the coral community.
The responses of small-scale coastal fisheries to pauses in effort and trade are an important test of natural resource management theories with implications for the many challenges of managing ...common-pool resources. Three Covid-19 curfews provided a natural experiment to evaluate fisheries responses adjacent a marine reserve and in a management system that restricted small-mesh drag nets. Daily catch weights in ten fish landings were compared before and after the curfew period to test the catch-only hypothesis that the curfew would reduce effort and increase catch per unit effort, per area yields, and incomes. Interviews with key informants indicated that fisheries effort and trade were disrupted but less so in the gear-restricted rural district than the more urbanized reserve landing sites. The expected increase in catches and incomes was evident in some sites adjacent the reserve but not the rural gear restricted fisheries. Differences in compliance and effort initiated by the curfew, changes in gear, and various negative environmental conditions are among the explanations for the variable catch responses. Rates of change over longer periods in CPUE were stable among marine reserve adjacent landing sites but declined faster after the curfew in the gear-restricted fisheries. Two landing sites nearest the southern end of the reserve displayed a daily 45 % increase in CPUE, 25–30 % increase in CPUA, and a 45–56 % increase in incomes. Results suggest that recovering stocks will succeed where authorities can achieve compliance, near marine reserves, and fisheries lacking additional environmental stresses.
•Fish catch before and after covid curfews was evaluated in gear and reserve management.•Curfew regulation compliance was higher near the reserve than gear managed sites.•Catch rates and incomes were variable but displayed greatest increases adjacent the reserve.•Rates of changes after the curfew mostly followed the longer-term trends in catches.•Curfew accelerated long-term declines in CPUE in gear-restricted but not reserves fisheries.
Reducing resource depletion and promoting ecosystem‐based management are considered key climate change adaptation policies. Therefore, the resource status of an identified climate refugia in a ...semi‐enclosed bay on the Kenya–Tanzania border was evaluated for sustainability. Both fisheries stock and catch assessment methods found low production and excess effort. Stock recovery in closures (up to 45 years) determined the best‐fit r and K values, which established a maximum sustainable production (MSY) of 2.98 ± 0.45 (SEM) tons/km2/year. Stock estimates in the bays' fishing grounds indicated that biomass was below the MSY and predicted to produce 1.8 ± 1.0 (SEM) or 1.1 ton/km2/year below the optimal MSY. However, landed fish at five studied fishing villages varied greatly from 0.22 to 2.9 tons/km2/year. MSY in the refugia was therefore considerably lower than estimates in nearby ocean‐exposed locations, which has been estimated at 5–7 tons/km2/year. Therefore, low to modest capture rates of fish will be required to allow the recovery needed to achieve sustainability and restore the refugia's ecology. The refugia's highest stocks and near‐MSY yields were captured in the national reserve. Therefore, broader implementation of the reserve's gear‐restriction policies should restore fisheries. High spatial variability in yield patterns indicate interactions between fisheries management, compliance, trade connections, and governance. In climate refugia, reducing cumulative impacts will require knowing and managing for lower fisheries production limits.
Fisheries production in a area identified as a climate refuge was estimated by stock and catch estimate methods. Results indicate low production and widespread overfishing apart from a gear‐managed marine reserve that should be used to guide future climate resilience policies.
•LEND/LRO instrument neutron counting data sets have been analyzed to create high resolution maps of epithermal neutron flux at polar regions of the Moon.•The conversion from epithermal neutron flux ...to the H/H2O abundances is presented based on the simple subsurface models.•The polar lunar maps (poleward 70S/70N) of homogeneous hydrogen distribution are derived and discussed.
We present a method of conversion of the lunar neutron counting rate measured by the Lunar Reconnaissance Orbiter (LRO) Lunar Exploration Neutron Detector (LEND) instrument collimated neutron detectors, to water equivalent hydrogen (WEH) in the top ∼1m layer of lunar regolith. Polar maps of the Moon's inferred hydrogen abundance are presented and discussed.
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