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1.
    
  1. Scutellastra mexicana is the largest species of giant limpet in the world. This species is distributed along the tropical Mexican Pacific and is now considered extinct in some areas of the region.
  2. In prehispanic Mexico, this limpet was used for food, ornamentation, and in mortuary offerings. More recently, its meat has been highly valued for human consumption. During the 1970s and 1980s, overexploitation of this resource caused the population to decrease drastically.
  3. This study is a report on the population status of the giant Mexican limpet S. mexicana on the Mexican Pacific coast. Free divers explored the rocky southern coast of Jalisco, Mexico, for the presence of specimens. A total of 404 limpets were identified at 18 sampling sites. Their density was estimated to be 0.0012 limpets/m2 with a catch per unit effort of 7.6 limpets/dive hour. Limpet sizes ranged from 5.0 to 23.3 cm in length and from 3.8 to 20.7 cm in width, with a mean shell length of 13.4 cm.
  4. Currently, S. mexicana is under special protection by Mexican laws. However, this species is not listed as endangered by any international wildlife protection and conservation group. This may be due to the lack of information on this species' population dynamics over time in the Mexican Pacific and the lack of interest in this mollusc since it is a non-charismatic species.
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2.
    
  1. Cetaceans occupying coastal habitats are at high risk of impact from anthropogenic sources which can cause direct mortality or affect long‐term health. Monitoring and detecting change require long‐term studies and reliable funding, not always available especially in developing countries. Management and conservation of cetaceans must therefore use precautionary methods that allow assessment from limited data sources to identify risk of, and prevent, species extirpation or extinction.
  2. IUCN Red List criteria for regional populations was applied to the population of Indian Ocean humpback dolphins (Sousa plumbea) resident in Menai Bay Conservation Area off the south coast of Zanzibar, East Africa which is subjected to unsustainable entanglement rates in gillnet fisheries and unregulated tourism activities. Photographic identification surveys were conducted in 2015 to generate a new abundance estimate from capture–recapture analysis. Mortality estimates were calculated using available data from 1999 to 2002 and a population viability analysis was conducted based on population, species and genus specific parameters.
  3. The 2015 abundance estimate for humpback dolphins was 19 (95% CI 14–25) non‐calf individuals, representing a 63% reduction in abundance since 2002. The population viability analysis baseline scenario predicted chance of extinction at 0.996 (SE 0.002) with the median time to extinction at 36 years. Sensitivity analysis suggested that population recovery would only be possible with a complete prevention of bycatch mortality.
  4. The population met the threshold for Critically Endangered for all criteria which could be directly assessed. This conservation assessment highlights the requirement for immediate management action to eliminate bycatch of humpback dolphins to prevent the local extinction of the species.
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3.
    
  1. Fin whales (Balaenoptera physalus) have been documented along the coast of Chile since the early 20th century; however, information on their ecology and movement patterns remains poorly known.
  2. In the spring of 2015, six implantable satellite tags were deployed on fin whales around the marine reserves of Isla Chañaral and Islas Choros‐Damas (approximately 29°S) to evaluate their movements and habitat use off the coast of Chile. A switching state–space model was used to estimate the predicted track of the whales as well as behavioural modes classified as ‘transiting’ and ‘area‐restricted search’ (ARS).
  3. Whales were tracked for periods ranging between 4 and 162 days (mean = 68 ± 52 days), covering an average distance of 3225.7 ± 2871.6 km. Five of the six whales remained at middle latitudes for prolonged periods of time, moving in a north–south pattern near the coast, and spending most of their time in ARS behaviour (72.5% of the locations). Only one individual showed a clear southbound migratory behaviour, and remained in transit behaviour for most of the period it was followed.
  4. These results suggest that some of the fin whales that are observed in Chile do follow a migration to high latitudes, whereas others remained at middle latitudes, probably using critical habitats as feeding grounds during the summer. This information not only contributes new information on the behaviour and foraging patterns of this species, but is also of particular interest to promote the growing whale‐watching activity, and also to better inform conservation and management efforts for this species in Chile.
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4.
    
  1. Patella ferruginea is an endemic and endangered limpet of the Mediterranean Sea. Its distributional range has been greatly reduced over the past century, mainly as a consequence of human pressure on coastal habitats, and its presence is now confined to a few sites in the western Mediterranean basin.
  2. It was assumed that the island of Mal di Ventre was the only location hosting P. ferruginea in the central‐western area of Sardinia (Italy), but reports from local people and the discovery of empty shells in surrounding areas suggested its distribution range may be greater than previously thought.
  3. Several systematic surveys for the presence of P. ferruginea were conducted during the summers of 2013 and 2014 at different locations of central‐western Sardinia to improve knowledge about its conservation status and to verify various reported occurrences.
  4. Findings from this study confirm the critical status of conservation of the species in central‐western Sardinia. The island of Mal di Ventre was confirmed as the main location hosting P. ferruginea and only one new small nucleus of limpets was found in a hardly accessible site on the coastline of the Sinis Peninsula (Cape San Marco). This nucleus represents the new southern distribution limit of the species in Sardinia.
  5. This work highlights the importance of awareness‐raising activities and local environmental knowledge (‘citizen science’) as a source of information that can result in a better understanding of the distribution of this endangered species. Hardly accessible sites represent ideal locations to put in place conservation measures for the local P. ferruginea population but further studies, specifically aimed at determining the larval dispersal and connectivity among different limpet nuclei, are required.
Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

5.
    
  1. The abundance, distribution and diet of the short-beaked common dolphin were investigated as part of the first detailed study on cetacean populations in the North Aegean Sea. Since 2004, the area has been proposed by national and international entities as a marine protected area for common dolphins and other cetacean species owing to its high biodiversity.
  2. Abundance and distribution were investigated between 2005 and 2013 through dedicated scientific marine transect surveys, covering 14,701 km, in sea conditions of Beaufort sea state 3 and below. The line-transect sampling method was used to estimate relative abundance, using Distance 6.0 software. Encounter rate for this species in the study area was estimated to be 0.24 groups/100 km (1.5 dolphins/100 km), with a mean group size of 6.88 (SE = 1.90).
  3. Common dolphin sightings were analysed for correlations with eight environmental variables (distance from the coast, depth, slope, median salinity, gradient of salinity, median temperature, gradient of temperature and mean current) using generalized additive modelling. Common dolphin sightings were significantly correlated to depth, temperature and salinity.
  4. Stomach-content analyses were performed on eight suitable samples from common dolphins stranded in the study area. The trophic level of the species was calculated, indicating that this species is a top predator.
  5. This research provides the first estimates for abundance and distribution and the first diet analysis for this Mediterranean Endangered dolphin species in the study area based on a year-round long-term study.
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6.
    
1. The relative abundances of two highly sought after spearfishing target‐fish species, Dicentrarchus labrax (Linnaeus 1758) and Sparus aurata Linnaeus 1758, were compared using underwater visual censuses in shallow (<5 m) inshore waters along rocky shores inside and outside a marine reserve area in the northwestern Mediterranean Sea (Banyuls‐sur‐Mer region, France). 2. The relative abundances of these two species were consistently lower outside the reserve area, which comprised around 40% of the 25.6 km of inshore coastal waters surveyed. 3. The demographic structure of D. labrax was also different inside and outside the protected area, the proportion of larger fish being significantly higher in the marine reserve. 4. The direct and indirect impacts of spearfishing are postulated to explain the distributional and population structural characteristics of these two species in the shallow waters off this rocky coast. 5. Prohibition of spearfishing has favoured the persistence of these species during summer (the main spearfishing season) in the shallower inshore waters inside the area of the Cerbère/Banyuls‐sur‐Mer marine reserve. 6. These preliminary results indicate the need for additional work in this area and further surveys to ascertain spearfishing impacts on target‐fish species in the vicinity of other marine protected areas. Copyright © 2001 John Wiley & Sons, Ltd.  相似文献   

7.
2003年8、12月和2004年2、5月对放鸡岛海域浮游动物的种类组成及分布进行了研究。结果表明：浮游动物以及浮游幼体12个类群共59种,其中浮游幼虫和水母类种类最多,分别为21种和13种。浮游动物群落可分为广布种、暖水性外海种和近岸低盐种3个生态类型。放鸡岛北侧近岸水域分布密度较高,而南侧外海水域分布密度较低。8月份平均个体密度最高21619ind．／m^3;12月份平均个体密度最低2370ind/m^3。桡足类和浮游幼虫是全年的优势类群,平均占到总体的67．56％和18．66％。多样性与均匀度指数变化是5月〉8月〉2月〉12月。  相似文献   

8.
    
1. Industrial fisheries represent one of the most serious threats worldwide to seabird conservation. Death of birds in fishing operations (i.e. bycatch) has especially adverse effects on populations of albatrosses, which have extremely low fecundity. 2. The single population worldwide of Amsterdam albatross (Diomedea amsterdamensis) comprises only 167 individuals and risks considerable decline over the mid‐term from additional mortality levels potentially induced by fisheries. The priority actions listed in the current conservation plan for this species included characterizing the longline fisheries operating within its range, dynamically analysing the overlap between albatrosses and these fisheries, and providing fisheries management authorities with potential impact estimates of longline fisheries on the Amsterdam albatross. 3. During all life‐cycle stages and year quarters the birds overlapped extensively with fishing effort in the southern Indian and Atlantic oceans. Fishing effort, and consequently overlap score (calculated as the product of fishing effort and time spent by the birds in a spatial unit) was highest in July–September (45% of the hooks annually deployed). Just three fleets (Taiwanese, Japanese and Spanish) contributed to >98% of the overlap scores for each stage (72% from the Taiwanese fleet alone, on average). Daily overlap scores were higher for the non‐breeding versus the breeding stages (3‐fold factor on average). 4. Based on previous bycatch rates for other albatross species, this study estimated that longline fisheries currently have the potential to remove ~2–16 individuals (i.e. ~5%) each year from the total Amsterdam albatross population, depending on whether bycatch mitigation measures were or were not systematically employed during the fishing operations. 5. Recent bycatch mitigation measures may be instrumental in the conservation of the Amsterdam albatross. This study suggests three further key recommendations: (1) to focus conservation efforts on the austral winter; (2) to require all operating vessels to report ring recoveries; and (3) to allocate special regulation of fishing operations in the areas of peak bycatch risk for the Amsterdam albatrosses. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

9.
    
  1. Elasmobranchs, encompassing an array of sharks and rays, confront a threat of extinction on a global scale. The Sea of Marmara (SoM) stands out as a critical refuge for these endangered species.
  2. This study harnesses data derived from comprehensive trawl surveys, representing the first area-based evaluation of the elasmobranchs inhabiting the SoM. Sampling protocols were carried out at 10 separate stations along the 980-km coastline of the SoM, each bounded by different ecological characteristics and anthropogenic influences.
  3. A total of eight shark species and six ray species were caught in the towed area of the entire the SoM. Notably, Scyliorhinus canicula and near-threatened Raja clavata constitute more than 50% of the total abundance. Additionally, rare, and critically endangered species, including the Oxynotus centrina, Squatina squatina, Dipturus batis, and Myliobatis aquila, were documented, expanding our knowledge of their presence in the region.
  4. Spatial distribution heterogeneity was pronounced within species.
  5. Size distributions were species-specific, and the presence of both juvenile and adult individuals suggested successful reproduction and growth.
  6. Records expand the known size range in the SoM for six shark and three ray species. It also provides first-size information based on the total length of the S. stellaris and D. batis.
  7. Additionally, the urgent need for field-based conservation efforts is highlighted, citing a previously unidentified important sensitive areas located in the southern part of the SoM.
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10.
    
  1. Seasonal trends in the distribution and relative abundance of southern right whales (SRWs) Eubalaena australis, were assessed in Australia's largest calving aggregation ground at the Head of the Great Australian Bight, in the Commonwealth Marine Reserve, South Australia. Annual cliff‐based surveys were undertaken between June and October from 1992 to 2016.
  2. SRWs were primarily distributed in a 15 km by 2 km area within the 10 m depth contour (with 95% of whale sightings made within a 10 km2 area). The distribution of SRWs at Head of Bight varied within an individual season but was consistent among the years. The composition of SRW sightings was 70% female–calf pairs and 30% unaccompanied whales.
  3. Peak abundance occurred between mid‐July and end‐August for female–calf pairs and unaccompanied whales (juveniles or adults not accompanied by a calf), earlier than previously reported. A mean of 16% (range 8–28%, SD = 6.5, 95% CI = 0.15) of calving females were present at the site in mid‐June and a mean of 37% (range 13–61%, SD = 15.8, 95% CI = 0.37) remained at the site at the end of September.
  4. Based on nearest‐neighbour distances of 150 m, the area occupied by 95% of SRWs at Head of Bight could reach carrying capacity at 68 female and calf pairs. Results suggest that the primary aggregation area at Head of Bight may have reached saturation capacity and that habitat expansion can be expected as the population increases.
  5. This study provides information on SRW seasonal trends in distribution and abundance, timing of arrival and departure from the site and peak abundance periods relevant to application to conservation and marine park management.
  6. As management requirements increase with a growing population, there is a need to complete an Australia‐wide assessment of SRW connectivity and habitat expansion.
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11.
  1. Effectiveness of restoration/repopulation measures may be strongly hindered by the ability of the target species to cope with the environmental conditions of the receiving area.
  2. Although a species has been reported previously for a given area, the environmental conditions and human pressures may have changed, potentially making any restoration attempt ineffective. Evidence is provided showing that the endangered ferruginous limpet Patella ferruginea can complete its reproductive cycle in the northernmost sector of the western Mediterranean.
  3. This supports the idea that the reintroduction and the strict protection of P. ferruginea in the extreme north of its historical geographic range could be effective for the recovery of the species in this area and ultimately the establishment of reproductively viable and stable populations.
  4. Verification of gonadal maturation of specimens experimentally established on the Gulf of Genoa (Ligurian Sea) coastline, as well as evidence of sex change in one individual (the first outside the Alboran Sea), provides further support of the potential for individuals to complete their reproductive cycle in this area.
  5. The results support the potential of actions for the restoration of viable populations of the species along the Ligurian coasts through the introduction of juveniles obtained exclusively by aquaculture techniques, in order to mitigate any impact on donor sites.
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12.
  1. The giant limpet Patella ferruginea is the most endangered endemic species in the Mediterranean Sea. It is at serious risk of extinction, especially along the coast of Corsica and Italy. The small population of P. ferruginea in the marine protected area (MPA) Penisola del Sinis ‐ Isola di Mal di Ventre (W Sardinia, Italy) is an isolated unit whose preservation is critical also from the perspective of conservation genetics.
  2. This study considered the impact of illegal harvesting on the conservation status of P. ferruginea in the MPA. Site accessibility (semi‐accessible and hardly accessible) and legal protection (Zone A, B, C) were considered in two field surveys conducted in the Mal di Ventre Island in 2011 and 2013. Furthermore, Zone A was monitored annually from 2009 to 2013 to assess population dynamics and extinction risk.
  3. In summer 2013 the total population size was estimated at 310 specimens (0.016±0.005 ind m‐1) with a significant decrease compared with 2011 (–52%), mainly due to poaching. Significantly higher density was found in the hardly accessible sites (0.039±0.007 ind m‐1 in 2013) and generally in Zone A (0.042±0.009 ind m‐1 in 2013). The size distribution showed a similar pattern, with larger sized individuals in those sites with maximum legal protection and a lower degree of accessibility. Juveniles (<25 mm) were almost absent and the mean individual growth rate (2.6±0.5 mm yr‐1) was lower in comparison with other Mediterranean populations. The population viability analysis predicted that, with current rates of harvesting, P. ferruginea may face local extinction within the next 10 years.
  4. Without a joint effort towards the protection of intertidal habitats by enforcement bodies, regulators, researchers and sea users, the MPA will not achieve its conservation objectives and P. ferruginea will disappear from Mal di Ventre Island. Copyright © 2015 John Wiley & Sons, Ltd.
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13.
    
  1. This study evaluated management effectiveness in three marine protected areas (MPAs) for conservation of the Antillean manatee (Trichechus manatus manatus Linnaeus 1758), located on the eastern coast of the Yucatan Peninsula, Mexico. The MPAs evaluated were the Yum‐Balam Flora and Fauna Reserve, Sian Ka'an Biosphere Reserve, and Chetumal Bay Manatee Sanctuary. The extent of the traditional, popular, and scientific manatee knowledge and research were assessed, as well as the prescribed conservation management actions, relevant stakeholders, and the degree of inclusion of manatee species in the management schemes of these MPAs.
  2. Four general criteria, 12 specific criteria, and 62 indicators were developed. In total, 199 interviews were completed in seven communities of the MPAs in order to determine the perception of the social, economic, and conservation impacts of the manatee and its management.
  3. Although the evaluated MPAs were not wholly comparable among themselves due to their different management categories and schemes, administration, socio‐economic context, and the dynamics and conflicts encountered, a comparison was conducted using standardized criteria and a categorical scale in order to evaluate the level of effectiveness of each MPA.
  4. The MPA with the highest management effectiveness in manatee conservation was found to be the Chetumal Bay, with an effectiveness classed as good (71%), followed by Sian Ka'an with intermediate effectiveness (53%) and Yum‐Balam, also with intermediate effectiveness (43%).
  5. The relationships between the key stakeholders of the three MPAs and economic activities such as fishing and tourism are the factors that most influence the effectiveness of management for manatee conservation.
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14.
    
  1. Cage diving is the most important activity for the sustainable use of white sharks (Carcharodon carcharias). However, information related to their behaviour during ecotourism is scarce.
  2. This study provides useful information for monitoring C. carcharias during cage‐diving activities around Guadalupe Island, Mexico. Surface behaviour of 106 white sharks was recorded for 87 days on‐board six cage‐diving boats in 2012, 2013, and 2014.
  3. Of the observed sharks, 63% were immature specimens (n = 67) and 37% were considered mature (n = 39). Seventy‐one per cent were males (n = 75) and 29% were females (n = 31).
  4. Interactions were classified into one of the 11 behaviours: parading, close inspection, horizontal attack, vertical attack, bait catching, feeding, not feeding, buoy catching, encounter, escape, and staying.
  5. Parading, close inspections, and horizontal attacks were performed more often by mature males, whereas immature females performed more vertical attacks, with no differences between mature and immature males.
  6. A total of 1,542 ethograms were registered. Each ethogram consisted on average of 6.3 ± 5.6 behaviours with a significant transitional pattern from horizontal attacks to parading and close inspections, and from vertical and horizontal attacks to bait being caught.
  7. A pattern related to feeding in a simple stimulus response reflex was observed. The shark's length seems to play an important role in the efficiency of the attacks, presumably resulting from the experience of mature individuals. Intentional feeding should be avoided to prevent negative effects related to ecotourism.
  8. This study constitutes a baseline for future research on white shark behaviour. It can be applied in other regions regardless of environmental conditions, quantity and size of the boats, and types of bait. Using this standard method could improve the monitoring, management, and conservation of this vulnerable species.
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15.
    
  1. Based on optimal foraging theory, animals are expected to maximize foraging benefits whilst minimizing risks. Despite risking being subjected to anthropogenic impacts such as water contamination, marine traffic, and underwater noise, estuaries have been identified as the preferred habitat of the Indo‐Pacific humpback dolphin (Sousa chinensis, IPHD). However, it remains unclear why this vulnerable species favours such risky habitats.
  2. Here, an exploratory case study in Zhanjiang estuary, China, was conducted to test the hypothesis that IPHDs select estuarine habitats as a trade‐off that maximizes foraging opportunities whilst minimizing the risk of mortality.
  3. The results showed that IPHDs accept greater mortality risks for higher food rewards but select habitats with lower risks when food rewards are similar between two locations.
  4. Although this type of information is important for underpinning models for individual dolphins, its principal role is to show environmental protection agencies why IPHDs favour estuaries despite the increased mortality risks.
  5. Habitat conservation plans should carefully consider prey stocks, possibly through the presence of marine protected areas near estuaries, as local overfishing may lead vulnerable cetacean populations to take greater risks.
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16.
  总被引：1，自引：0，他引：1  
  • 1. Four macroalgal, four macroinvertebrate and eight fish species were surveyed at eight sites (three inside, five outside the proposed reserve) over three years before the establishment of the Taputeranga Marine Reserve (MR) on Cook Strait (Wellington, New Zealand). This baseline data set was used to estimate temporal and spatial variability in size and abundance of these taxa, and will be used to quantify taxon‐specific changes in size and abundance once the MR is established.
  • 2. Statistically significant differences in size and/or abundance were observed for many taxa among the sites. These differences are consistent with the existence of a natural environmental gradient from the west (entrance to Cook Strait) to the east (Wellington Harbour). This gradient highlights the importance of conducting a pre‐reserve baseline survey at multiple sites and over multiple years to better understand the conservation or fisheries benefits that MRs are expected to deliver.
  • 3. Two macroalgal, one macroinvertebrate, and six fish species showed statistically significant seasonal variation in abundance. Subsequent multi‐taxa monitoring needs to include a seasonal component to capture this natural variability.
  • 4. This multi‐site and multi‐year data set represents one of the most comprehensive and robust baseline data sets available anywhere in the world. It will be used to quantify the ecological changes associated with a newly established full no‐take marine reserve. Ongoing monitoring will enhance understanding of the sizes and abundances of key taxa, allow a detailed determination of the conservation effects of reserve establishment, and inform management decisions for Wellington's south coast.
Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

17.
    
  1. Tourist‐based activities, partly due to their rapid increase, have raised concerns regarding the impacts of anthropogenic activity on marine fauna. Documented effects on pinnipeds in proximity to humans include changes in behaviour, site use and potentially higher aggression levels towards people. Effects vary considerably between populations and sites, thus requiring separate assessment of human impacts on activity and energy budgets.
  2. Responses of the endangered Australian sea lion, Neophoca cinerea, to human visitation were recorded from November 2013 through April 2014. Exposure levels and response types to anthropogenic activities were assessed at two easily accessible locations with different management schemes, Seal (landing prohibited) and Carnac (landing permitted) islands, Western Australia. Exposure levels were measured as both stimulus type (i.e. ‘People’, ‘Paddlers’, ‘Small’, ‘Medium’, and ‘Large vessels’, ‘Tour vessels’, and ‘Jet skies’), and people (‘Direct’, ‘Attract’, ‘Interact’, ‘View’, ‘Incidental’, ‘Water’, ‘Low‐level’), and vessel activities (‘Interact’, ‘Approach/Follow’, ‘Anchor noise’, ‘Engine noise’, ‘Close to beach’, ‘Moderate/Fast travel’, ‘Slow travel’, ‘Transit’, ‘Drift/At anchor’, ‘Aircraft noise’).
  3. Exposure levels varied significantly between the islands in numbers, stimuli type, duration and minimum approach distances. The instantaneous behaviours of ‘Lift head’, ‘Interact’ and ‘Sit’ were the most frequent responses. ‘Aggressive’ and ‘Retreat’ responses, the highest disturbance levels measured, occurred on Carnac approximately once per day, but rarely on Seal Island. ‘Aggressive’ behaviour towards ‘People’ was observed only on Carnac Island and elicited only by ‘People’. ‘People’, ‘Tour vessels’, and scenic ‘Aircrafts’ on both islands as well as ‘Jet skis’ on Carnac Island had the highest probability of triggering responses. Owing to their relatively high visitation at Seal Island, ‘Paddle powered vessels’, followed by ‘Tour vessels’ elicited the highest number of responses, compared with ‘People’, ‘Small’, and ‘Medium vessels’ at Carnac Island. The majority of responses occurred when any stimulus type was at short‐range (≤10 m), and ‘People’ ‘Viewing’ N. cinerea elicited most. Vessels triggered more responses at larger ranges than ‘People’.
  4. To limit close‐range access to N. cinerea, one possibility is to close the beach at Carnac Island to human visitation and increase the minimum approach distance by vessels and ‘People’ by installing marker buoys at least 15 m from the shore.
© 2016 The Authors. Aquatic Conservation: Marine and Freshwater Ecosystems published by John Wiley & Sons, Ltd.  相似文献   

18.
    
  1. Knowledge of vital data such as growth and age at maturity is necessary to develop effective management strategies for endangered species. The Critically Endangered flapper skate (Dipturus intermedius) is the largest skate in the North Atlantic and growth information, necessary to assess key life-history traits, populations’ growth rates and anticipate their response to management measures, is still lacking.
  2. While classical age estimation methods used in fish generally require the analysis of calcified structures, destructive methods are incompatible with conservation objectives for this species. Taking advantage of the high recreational value of the flapper skate, this study uses citizen-science data originating from photo-identification of trophy pictures and tag–recapture data supported by anglers to estimate growth in this Critically Endangered species. Using the growth increments measured between recapture events, an individual-based Von Bertalanffy growth model was fitted to the data using Bayesian inference.
  3. The results confirm that the flapper skate is a long-lived species with ages estimated as >40 years for the largest individuals captured. Despite this longevity, the model reveals a relatively fast initial growth but relatively late ages at maturity and significant sex-related differences in both growth rate and maximum size.
  4. These results suggest that population growth rate, and therefore recovery, might be much slower than previously reported. By using citizen science this study provides the necessary information to begin understanding population dynamics and monitor the recovery of an iconic Critically Endangered species.
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19.
    
  1. An aggregation of sandbar sharks Carcharhinus plumbeus occurs every summer around the remote uninhabited islet of Lampione (Pelagie Islands Marine Protected Area, south-western Mediterranean Sea), attracting an increasing number of tourists for a shark watching experience.
  2. Despite the ecological and socio-economic importance of this rare occurrence in Mediterranean waters, there is a lack of scientific data and lack of information as to the potential impact of tourist activities on the presence and behaviour of this shark species.
  3. Using baited underwater videos, this study provides the first assessment of this shark aggregation, as well as a preliminary evaluation of the potential effects that boating and diving activities may have on sandbar sharks during two different periods within the tourism season (July and September 2019).
  4. Overall, 241 sandbar shark sightings (with up to five individuals together) were recorded in July, whereas there were only six sightings in September. The average MaxN was 1.18 hr−1 (±0.21 hr−1 SE) and 0.22 hr−1 (±0.10 hr−1 SE) individuals in July and September respectively. Higher frequentation levels of divers and boats significantly reduced the number of shark sightings at the aggregation site.
  5. This study emphasizes the need for further investigations on Mediterranean shark aggregations and the implementation of specific conservation measures, such as an increase of protection level in Lampione and better enforcement, aside from strategies that promote sustainable tourism, including restrictions on the number of boats and divers’ visits per day. In the meantime, a precautionary approach aimed at regulating the interactions between tourists and sharks should be implemented through the application of a self-regulatory code of conduct for divers when sharks aggregate around the island.
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20.
    
  1. Monitoring fish movement can test the effectiveness of environmental flow releases when they are used to trigger spawning behaviour. Environmental flow releases have been used to enhance Australian grayling (Prototroctes maraena) spawning in regulated rivers in south‐eastern Australia and resource managers require knowledge of the effectiveness on the conservation of this threatened species.
  2. Australian grayling movement was monitored in the Thomson River, south‐eastern Australia using acoustic telemetry to determine whether the species undergoes a spawning migration, where they migrate and timing in relation to environmental flow releases. Drift netting was used to verify whether spawning took place.
  3. Adult Australian grayling undertook downstream spawning migrations (up to 140 km) to the lower Thomson River, coinciding with environmental flow releases.
  4. The findings of this study support the use of environmental flow releases to trigger spawning migrations by Australian grayling. In addition, they provide managers of other species with an example of the potential effectiveness of environmental flow releases in triggering fish migration or spawning that can assist in rationalizing this management intervention.
Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

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