Using T‐PODs to assess variations in the occurrence of coastal bottlenose dolphins and harbour porpoises

• 1. Assessments of anthropogenic impacts on cetaceans are often constrained by limited data on the extent to which these species use particular areas.
• 2. Timing porpoise detectors (T‐PODs) are autonomous data recorders for detecting cetacean echolocation clicks, potentially providing cost‐effective opportunities for monitoring cetacean occurrence.
• 3. The performance of T‐PODs was assessed in three areas off the Scottish east coast, where the relative occurrence of bottlenose dolphins and harbour porpoises was known to differ. Land‐based observations in one area compared visual and acoustic detections of dolphins, while direct hydrophone recordings of dolphin echolocation clicks were compared with T‐POD detections during boat surveys.
• 4. Land‐based surveys recorded 89 groups of dolphins within 900 m of the T‐POD. All groups spending >30 min in the area were detected on the T‐POD, and the probability of detection declined in relation to distance from the recording site.
• 5. The number of dolphin clicks recorded on the independent hydrophone system was significantly related to the number detected by a T‐POD. Between pairs of T‐PODs, there was also significant correlation with the numbers of clicks recorded in each hour, both for channels set to detect bottlenose dolphins and for channels set to detect harbour porpoises.
• 6. Year‐round deployments of paired T‐PODs detected significant geographical variation in detections for both bottlenose dolphins and harbour porpoises. This pattern reflected published data from visual surveys, where dolphins occurred most regularly within the Moray Firth Special Area of Conservation, and porpoises were sighted more regularly in offshore waters.
• 7. T‐PODs do not detect all cetaceans in the area, and care must be taken when interpreting data from mixed species communities. Nevertheless, these results confirm that T‐PODs provide an effective method for monitoring the occurrence of bottlenose dolphins and harbour porpoises, and provide excellent potential for collecting baseline data from poorly studied areas and monitoring long‐term temporal change in key areas of interest. Copyright © 2009 John Wiley & Sons, Ltd.

     

Long‐term habitat loss in a lightly‐disturbed population of the Indo‐Pacific humpback dolphin,Sousa chinensis

相似文献   

Challenges in monitoring mobile populations: Applying bayesian multi‐site mark–recapture abundance estimation to the monitoring of a highly mobile coastal population of bottlenose dolphins

1. Monitoring the abundance of mobile and wide‐ranging cetacean populations for conservation management is challenging, especially when the management is focused on static protected areas. Where abundance estimates are derived from mark–recapture data, such as photo‐identification of naturally marked individuals, unpredictable movements of animals in and out of the survey area can reduce ‘capture’ probabilities and affect the precision and accuracy of resulting estimates.
2. A Bayesian hierarchical log–linear model was applied to photo‐identification data collected in summer 2014 to derive a multi‐site abundance estimate for a population of bottlenose dolphins, Tursiops truncatus, ranging widely throughout the coastal waters of western Ireland. In addition, the effects of varying levels of sampling effort on the minimum detectable decrease in population size were examined.
3. The abundance (median) of dolphins was estimated as 189 (coefficient of variation (standard deviation/mean), 0.11; 95% highest‐posterior density interval, 162–232). Over 50% of the well‐marked dolphins encountered throughout the study were sighted in more than one distinct coastal area, thus displaying high mobility. In addition, it was found that it would require biennial surveys to detect a 25% decline in abundance within the six‐year reporting period of the EU’s Habitats Directive.
4. Given that the Special Area of Conservation designated for these dolphins consists of two separate areas covering a substantial portion of the west coast of Ireland, the multisite approach is appropriate for monitoring this population. It produces a more precise estimate and is well suited for sparse recapture data collected opportunistically at multiple sites, when the lack of resources prevents large‐scale surveys or when concentrating surveys on smaller localized areas fails to capture the broad range and unpredictable occurrence of the animals. The Bayesian multi‐site approach could be applied to the management of other wide‐ranging marine or terrestrial taxa.

     

A comparative analysis of habitat quality between artificial and natural creeks in the Mediterranean killifish Aphanius fasciatus: Implications for conservation

1. In transitional water ecosystems, habitat loss is one of the major threats to fish biodiversity. This is particularly true in the case of temperate salt marshes. Good quality artificial novel habitats may compensate for the loss of natural habitats, acting as a refuge for fish populations.
2. The aim of this study was to use coloured ornamental traits exhibited by the males of a small lagoon-resident fish, the Mediterranean killifish Aphanius fasciatus (Valenciennes, 1821), to assess habitat quality in both the natural and artificial creeks of the Venice lagoon.
3. The conspicuousness of two secondary sexual traits, the yellow/orange caudal fin pigmentation and the contrast between white and dark vertical bars on body sides, proved to be greater in artificial habitats compared to natural salt marshes, highlighting the refuge function of artificial creeks.
4. The use of secondary sexual traits could be extended to other fish species and to other aquatic habitats as a non-invasive approach. This would allow the identification of good quality habitats in the context of fish population management and conservation.

     

Predictive spatial modelling of seasonal bottlenose dolphin (Tursiops truncatus) distributions in the Mississippi Sound

相似文献   

Changing distribution of the east coast of Scotland bottlenose dolphin population and the challenges of area‐based management

相似文献   

Common bottlenose dolphin (Tursiops truncatus) interaction with fish farms in the Gulf of Ambracia,western Greece

1. Marine aquaculture, and its fast-growing development, has the potential for wider environmental, ecosystem, and biodiversity impacts. This study assesses the impact of fish farming on a bottlenose dolphin (Tursiops truncatus) population within the Gulf of Ambracia (western Greece) between 2007 and 2018. Two different study areas were defined in order to investigate differences on occurrence, abundance, behaviour, and seasonal fluctuations between them: a ‘control area’, in the north-western side of the Gulf; and a ‘fish farm area’, in the south west, where the highest density of fish farm cages is found.
2. A total of 169 daily surveys were dedicated to the control area and 74 days were dedicated to the fish farm area, yielding 104 and 37 sightings, respectively. Both the probability of detecting dolphins (U = 6,763.000, P = 0.002) and the group sizes (U = 578.000, P < 0.001) were smaller around fish farms.
3. Seasonality analyses were restricted to 2007–2008, as this was the period with year-round effort. Results revealed that dolphins were more frequently seen around fish farms in the winter (Kruskal–Wallis test, P = 0.036).
4. From the 40 identified individuals that were re-sighted at least 10 times during the study period, 21 used the fish farm area less than expected according to sampling effort, and 10 of them were never observed in that area (binomial test, P < 0.05).
5. The results revealed an impact of fish farms on the distribution of bottlenose dolphins in the Gulf of Ambracia. This information should be taken into consideration when defining ecosystem-based management measures within the management plan, which is currently in preparation for this Natura 2000 site.

     

Site‐fidelity and movement patterns of bottlenose dolphins (Tursiops truncatus) in central Argentina: essential information for effective conservation

相似文献   

Decreasing population trend in coastal bottlenose dolphin (Tursiops truncatus) from the Gulf of Guayaquil,Ecuador

相似文献   

Using aerial photography for identification of marine and coastal habitats under the EU's Habitats Directive

• 1. Implementation of the E.U. Habitats Directive requires information on the distribution, abundance and area covered by the habitats listed in Annex I of the Directive.
• 2. In Finland, 21 of these habitats occur in marine and coastal areas. The demand for spatial information of these habitats is increasing, so rapid and relatively inexpensive mapping methods are needed.
• 3. This study examines the identification of 15 habitats using high altitude black and white aerial photographs. Our goal was to find out how well these habitats could be identified using these types of photographs. We used a test group of 34 persons who were given only brief instructions on how to identify the habitats prior to the test. Their results were compared to a set of field data from an archipelago area at the entrance of the Gulf of Finland, in August 1999 and autumn 2000.
• 4. The test group identified sandy beaches, lagoons, submerged sandbanks and cliffs with an accuracy of 82%, 71%, 66% and 65%, respectively. The main reasons for these high accuracy percentages were apparently the high contrast and/or easy delineation of the habitat from the surrounding areas.
• 5. Reefs, wooded dunes and submerged reefs were identified with an accuracy of 39%, 44% and 45%, respectively. The remaining habitats were less precisely identified, apparently due to their small size or poor contrast to the surrounding areas.
• 6. High altitude aerial photographs are shown to be a useful tool for identifying several of these habitats and can be used as a complement to field mapping methods, GIS methods and other remote sensing techniques. The use of high altitude photographs for monitoring change is discussed.

Copyright © 2002 John Wiley & Sons, Ltd.     

江苏启东近岸海域大型底栖动物群落健康评价

海洋大型底栖动物能对自然和人为活动导致的水和沉积物质量变化做出可预测的响应,因此利用底栖生物作为海洋生态环境监测的生物指标和进行系统健康度量的生物指数已经得到了广泛的认可。AMBI指数(AZTI’s Marine Biotic Index)法、ABC(abundance/biomass comparison)曲线法和BENTIX指数法可以有效地评价河口和近岸海域大型底栖动物群落对人为和自然扰动的响应。在2013年1、6、8、11月分别对启东近岸海域的大型底栖生物进行了调查,对比分析了4个季节大型底栖生物种类数、优势种、密度和生物量的差异,并运用ABC曲线法、AMBI和BENTIX指数法评估了调查海域大型底栖动物群落的受干扰状况。结果表明,该海域共采集大型底栖动物86种,其中优势类群为多毛类。群落中的优势种类主要为钩虾(Gammarus sp.)。调查海域年平均总生物量和丰度分别为6.92g·m-2和84.33 ind·m-2,且存在季节性差异。根据ABC法、AMBI法和BENTIX指数法分析显示绝大部分区域受到轻微程度人为的干扰,特别是夏季受到干扰程度较为强烈。研究结果表明,启东近岸受一定程度人类活动影响。     

A cost‐effective model for preliminary site evaluation for the reintroduction of a threatened quillwort

相似文献   

Food risk trade‐off in the Indo‐Pacific humpback dolphin: An exploratory case study

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.

     

Using fishers’ ecological knowledge to assess the status and cultural importance of sawfish in Guinea‐Bissau

相似文献   

Effects of differing ground‐truth data,transect design and statistical analysis on the repeatability of hydroacoustic assessments of pollan Coregonus autumnalis pollan

Pollan, Coregonus autumnalis pollan Thompson, requires an appropriate standardised sampling protocol for conservation assessments. The suitability of hydroacoustics with gillnetting was evaluated, and the effects of sampling design, effort and statistical analysis on the repeatability of results were tested. Summer hydroacoustic surveys appear appropriate as pollan were not abundant in acoustically unsampled areas. However, pollan density estimates were significantly affected by the gillnet sampling design used to ground‐truth the acoustic data. Density estimates from the >12‐ m layer were more robust to gillnet design than estimates from the 3‐ to 12‐ m layer. Estimates from different transect designs yielded some statistically significant results. Comparison of transects common to both transect designs suggests that observed differences reflect temporal changes rather than transect design effects. The reduction in the systematic parallel transect effort by half significantly affected target strength distributions but not pollan density estimates. Density estimates were affected by statistical analysis method where pollan density was highest, with geostatistical analysis providing higher estimates than the arithmetic mean. Hydroacoustic assessments may provide a reliable index of pollan abundance over time and between lakes but future research should investigate the effects of temporal and abiotic factors.     

Social structure in a critically endangered Indo‐Pacific humpback dolphin (Sousa chinensis) population

相似文献   

Preliminary recovery of coastal sharks in the south‐east United States

Relative abundance of many shark species in the Atlantic is assessed by compiling data from several independently conducted, but somewhat spatially limited surveys. Although these localized surveys annually sample the same populations, resulting trends in yearly indices often conflict with one another, thereby hindering interpretation of abundance patterns at broad spatial scales. We used delta‐lognormal generalized linear models (GLMs) to generate indices of abundance for seven Atlantic coastal shark species from six fishery‐independent surveys along the US east coast and Gulf of Mexico from 1975 to 2014. These indices were further analysed using dynamic factor analysis (DFA) to produce simplified, broad‐scale common trends in relative abundance over the entire sampled distribution. Effects of drivers including the North Atlantic Oscillation index, the Atlantic Multidecadal Oscillation index, annually averaged sea surface temperature and species landings were evaluated within the DFA model. The two decadal oscillations and species landings were shown to affect shark distribution along south‐east US coast. Estimated common trends of relative abundance for all large coastal shark species showed similar decreasing patterns into the early 1990s, periods of sustained low index values thereafter and recent indications of recovery. Small coastal shark species exhibited more regional variability in their estimated common trends, such that two common trends were required to adequately describe patterns in relative abundance throughout the Gulf of Mexico and Atlantic. Overall, all species’ (except the Gulf of Mexico blacknose shark) time series concluded with an increasing trend, suggestive of initial recovery from past exploitation.     

Using low‐cost drones to monitor heterogeneous submerged seaweed habitats: A case study in the Azores

相似文献   

The ecology of the endemic quillwort Isoëtes malinverniana: From basic research to legal and in situ conservation

1. Scientific publications on the conservation of threatened species can drive practical conservation solutions for endangered species. Yet, a posteriori assessment of the impact of such publications is rarely seen in the scientific literature.
2. The impact of two articles published in Aquatic Conservation: Marine and Freshwater Ecosystems (AQC) on the conservation of the endangered quillwort Isoëtes malinverniana is assessed. The articles were the result of a 10‐year study on the focal species that eventually led to the first reintroduction of I. malinverniana. The first article described the development of a cost‐effective model for the selection of suitable reintroduction sites for the species. The second article provided a summary of the techniques used to reintroduce the species and included techniques of ex situ propagation, recipient site preparation, planting methods, and monitoring.
3. This article reviews the practical conservation actions for I. malinverniana that followed the publication of two AQC papers and how they may affect research and conservation for other quillworts and aquatic macrophytes.
4. The results were surprising and went well beyond the initial expectations of the authors. Both AQC publications stimulated the conservation of I. malinverniana from different points of view. They contributed by informing scientists and policymakers of the risk of extinction of this species, leading to the establishment of a new protected area in Piedmont (northern Italy).
5. Our published data represent a sound starting point for funding opportunities in the context of the European Union LIFE programme. Further impacts include an expansion of knowledge on oligotrophic habitat management, the assessment of conservation status, and the education of the general public, with the last of these greatly enhanced by the two ex situ collections created in the botanic gardens of Tourin and Pavia. Interestingly, other authors are now using our approach in research and conservation on other endemic and endangered quillworts worldwide.