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1.
    
  1. The Colorado River Delta is one of the most impacted wetland systems in the world and has experienced massive habitat loss owing to severe restrictions in freshwater inflow as a result of dam construction and diversion of water for irrigation. However, the delta still offers nesting and foraging habitats for waterbirds, although the habitats available are highly fragmented and limited.
  2. Stable isotope ratio (SIR) analysis was used to assess quantitatively isotopic niche width of gull‐billed terns (Gelochelidon nilotica), laughing gulls (Leucophaeus atricilla) and snowy egrets (Egreta thula) that nest at an inland and coastal location.
  3. The variance in carbon and nitrogen SIR of egg albumen indicated that inland colonies have a much broader isotope niche width (range 2.9 to 23.9) than coastal colonies (<0.1 to 1.4).
  4. Species‐specific mean albumen δ13C values from inland nests were significantly more depleted in 13C than coastal colonies (?19.5 to ?23.1‰ and ?10.4 to ?14.9‰, respectively). Comparison of albumen δ13C values corrected for trophic fractionation with those of potential prey and primary producers collected at 10 potential foraging grounds indicates that females of the three species that nest in inland colonies did not feed in habitats located in the vicinity of their nesting site, while coastal colonies had distinct isotopic signatures reflecting marine primary production. Inland colonies probably forage in a variety of habitats and for different prey, relying on food webs based mostly on C3 terrestrial plants.
  5. Differences in the isotopic composition of eggs from species nesting in the same area and between conspecifics nesting in different habitats indicate that foraging habitats vary substantially, suggesting that feeding varies as a function of local resource availability.
  6. These results suggest that a variety of habitat types fulfill the foraging needs of this suite of nesting waterbird species, especially in inland colonies. Since the specific feeding areas of nesting females from the inland colonies have not been identified, protection of the remaining wetlands within the Colorado River Delta is warranted.
Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

2.
    
  1. In the coastal environment, marine mammals are exposed to one of the fastest growing food production sectors; namely, the shellfish farming industry. Identification of critical habitats, such as foraging grounds in highly human‐impacted areas, is essential to species conservation. Therefore, understanding the variables that influence a species' foraging behaviour is important for their conservation, especially for long‐lived mammals such as cetaceans.
  2. The aims of this study were (a) to identify and quantify the environmental and anthropogenic drivers of wild bottlenose dolphin (Tursiops truncatus) foraging behaviour, and (b) to investigate whether the shellfish farming industry influences the behaviour of this species.
  3. Behavioural observations were conducted along the north‐western coast of Spain, an area affected by intensive human activities, particularly the shellfish aquaculture industry.
  4. A multi‐modelling approach highlighted the importance of shellfish farm areas as a foraging ground for bottlenose dolphins. Dolphins were predicted to be more likely found foraging inside shellfish farm areas than outside (57% vs. 43%).
  5. Variability in bottlenose dolphin behaviour is likely a result of the interactions of environmental and anthropogenic drivers with prey availability and the physiological needs of the dolphins. Although shellfish farm areas provide high prey density for dolphins, they can also pose threats in a number of ways (i.e. collisions with vessels, entanglement with ropes, habitat loss, noise and water pollution).
  6. From a conservation perspective, aquaculture management should consider the presence of dolphins foraging and minimize the associated risks that this industry may pose to these coastal cetaceans.
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3.
    
  1. Seahorses are marine fish with several life history characteristics hypothesized to make them resilient but are of conservation concern because of their international trade and habitat loss.
  2. Surveys of two unexploited European seahorse species (Hippocampus guttulatus and Hippocampus hippocampus) in Ria Formosa lagoon, Portugal, were repeated seven years after their populations in the lagoon were found to be among the densest in the world.
  3. Population densities of both species declined significantly between 2001/2002 and 2008/2009 surveys (94% and 73% for H. guttulatus and H. hippocampus respectively). H. guttulatus declines were not associated with any environmental changes measured (i.e. percentage live benthic habitat cover, depth, temperature, water current speed, horizontal visibility). H. hippocampus declined more where current speed had decreased.
  4. At the low densities found in 2008/2009, occurrence for both species was best predicted by depth: seahorses were found in deeper locations throughout the lagoon. Other important predictors were temperature for H. guttulatus (found at sites warmer than average) and current speed for H. hippocampus (found in locations with faster currents).
  5. The large declines in seahorse densities made it difficult to compare results over time. Presence–absence and abundance modelling at multiple scales can help to ensure that data are comparable even when populations fluctuate drastically.
Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

4.
    
  1. Accurately mapping the extent and status of biogenic reefs formed by polychaete worms of the genus Sabellaria is of conservation importance given their protected status across Europe.
  2. Traditionally, side‐scan sonar (SSS) combined with ground‐truthing in the form of seabed photography and videography has been widely accepted as the most suitable approach for mapping these reefs in the subtidal zone. In highly turbid environments visibility at the seabed can be near zero, however, rendering optical‐based ground‐truthing redundant. Consequently, the true distribution and status of Sabellaria reefs in some shallow subtidal areas around the UK remains unclear despite their designation as Annex‐I features of several Special Areas of Conservation (SACs) under the Habitats Directive.
  3. Acoustic camera imagery (ACI) collected using acoustic cameras in two deployment configurations matched well with the backscatter signatures of seabed features in corresponding SSS data. The ACI was of suitable resolution for visualizing Sabellaria colony structures, allowing for their Annex‐I ‘reef’ defining attributes (extent, patchiness, and elevation) to be assessed. Colony formation ‘type’ was also distinguishable in the ACI, although confidence in differentiating between low‐lying Sabellaria formations and surrounding substrates was low, particularly when using a pole‐mounted configuration.
  4. This study provides a proof of concept for using acoustic cameras as tools for ground‐truthing SSS interpretation and assessing the status of Sabellaria bioconstructions in low‐visibility environments. Further development of this approach and incorporating it into statutory monitoring programmes could improve the management of the reef habitats in subtidal areas of the Severn Estuary and other highly turbid environments.
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5.
    
  1. Species distribution modelling has been used to identify critical habitats for the delimitation of Marine Protected Areas. Although Marine Protected Areas may often overlap with the distribution of key marine species, illegal human activities often continue within these areas, causing negative impacts on the local biodiversity.
  2. A generalized linear model with spatial eigenvector mapping was used to investigate, for the first time, the influence of environmental variables and anthropic activities on the number of Guiana dolphin, Sotalia guianensis sightings/grid, and to determine whether a Marine Reserve, in south‐eastern Brazil, is adequate for the protection of the local population. Data were collected between May 2007 and October 2013 onboard a 7.5‐m vessel with an inboard engine.
  3. The models for the different periods (annual, dry, and rainy seasons) all indicated that depth, the distance to seafood farms and fishing grounds, and mean sea surface temperatures influenced the distribution of the dolphins within the study area. The annual and seasonal models predicted that the dolphins prefer a continuous area between Cedro and Pico Islands, a large area that lies outside the limits of the Marine Reserve.
  4. Although the habitat of Ilha Grande bay is still much less degraded than that inhabited by other nearby Guiana dolphin populations, the results of the present study indicate that anthropic activities in this area influence habitat use by the dolphins. Less than 30% of the area used by the dolphins is protected by the Tamoios Ecological Station (ESEC Tamoios).
  5. Sotalia guianensis is classified as ‘Vulnerable’ in Brazil, although the marine reserve (ESEC Tamoios) does not protect the core area used by the local dolphin population. The results of the present study provide specific locations for the creation of a new multiple‐use MPA, as suggested by the Brazilian National Action Plan for the Conservation of Small Cetaceans, or the inclusion of a special management programme for the area between Cedro and Pico islands to better protect the dolphins in the ESEC Tamoios buffer zone. The continuation of surveys to better understand the current and future impacts of human activities, and the development of a closer interaction with both the local community and local stakeholders will help to safeguard Ilha Grande Bay and the local Guiana dolphin population.
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6.
    
There is generally a very poor understanding of how anadromous brown trout, Salmo trutta, use marine ecosystems. In this study, we use acoustic telemetry techniques to test four alternative hypotheses for estuarine coastal habitat use by this species on a population in the Clyde, west-central Scotland. Anadromous brown trout in their second (or more) summer feeding in the marine environment did not show patterns of estuarine use predicted from studies on other populations of this species. They did not (a) use the inner Clyde Estuary as a staging post for onward migration to open coastal waters, nor did they (b) pass through the estuary rapidly nor did they (c) make multiple incursions into freshwater. In contrast, fish utilised a very geographically constrained area of the inner estuary (<8 km in length), within which fish were highly mobile, exhibiting more activity during a flooding tide and exhibited high survivorship compared with reports from other studies. The reasons why estuarine use by anadromous brown trout in the Clyde may differ from that reported elsewhere is discussed.  相似文献   

7.
    
  1. The population status of the coastal bottlenose dolphin (Tursiops truncatus) inhabiting the inner estuary of the Gulf of Guayaquil, Ecuador (3°S, 81°W) was assessed. Evaluated aspects included social organization, abundance and spatial distribution.
  2. Surveys focused on the western part of the estuary (Posorja and Estero Salado) but other areas in the central and eastern inner estuary were also surveyed.
  3. Effort included 68 trips, 5001 km of survey and 288.8 h at sea. Between 735 and 793 dolphins in 92 groups were recorded during the study.
  4. Dolphins are not evenly distributed but concentrated their activities in the mouths of large channels.
  5. A cluster analyses indicated that dolphins organize in partially discrete subunits referred to as communities.
  6. Abundance estimations were obtained using mark–recapture modelling for two communities: Posorja and Estero Salado (43 dolphins, 95% CI 37–49 and 65 dolphins, 95% CI 52–82 respectively).
  7. Four demographic parameters: average size of communities, average group size, average encounter rate and average density were compared with information obtained during the 1990s. In all cases the current values were between 39 and 54% lower; in the last three cases the difference was statistically significant.
  8. Possible causes of this apparent decline include bycatch, ship strikes, pollution and habitat degradation; however, none of these have been assessed in depth. Most probably, different stressors are affecting dolphin communities to different extents.
  9. A comprehensive assessment of the whole population inside the gulf is needed. Identifying major threats is a priority to define concrete actions to prevent further population decline.
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8.
    
  1. The effectiveness of conservation measures such as marine protected areas (MPAs) for the conservation of cetaceans is determined by how well their home range or critical habitat is covered. The present study seeks to provide information on the site‐fidelity and movement patterns of individual bottlenose dolphins (Tursiops truncatus) in central Argentina.
  2. Between 2007 and 2013, photo‐identification data of bottlenose dolphins were collected in four study sites some 90–200 km apart from each other along the central Argentinean coast.
  3. Results show long‐term site‐fidelity (over 5 years) in one of the study areas. Re‐sighting rates further suggest the existence of different sub‐populations of bottlenose dolphins, but also confirm some connectivity (with movements over 200–290 km) and thus potential for gene flow within the region.
  4. Considering the population declines of bottlenose dolphins in Argentina, information on site‐fidelity and movement patterns will be of value to improve the effectiveness of existing MPAs for the conservation of the species as well as prioritizing areas for increased research.
Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

9.
    
  1. Sawfish are arguably the world's most imperilled marine fishes. All five species are classified as highly threatened with extinction: three are Critically Endangered (smalltooth sawfish Pristis pectinata, largetooth sawfish Pristis pristis, and green sawfish Pristis zijsron); two are Endangered (narrow sawfish Anoxypristis cuspidata, and dwarf sawfish Pristis clavata).
  2. Sawfishes are threatened primarily due to a combination of their low intrinsic rates of population increase, high catchability in fisheries, and high value. Sawfishes are among the world's largest marine fishes, and they are caught by a wide range of fishing gears owing to their tooth‐studded rostra being easily entangled. Sawfish fins are some of the most valuable for shark fin soup, and their rostra have long been traded as curios. In addition, they inhabit shallow coastal waters, estuaries, and rivers of the tropics and subtropics, down to a maximum depth rarely exceeding 100 m and are associated with threatened mangrove and seagrass habitats.
  3. Historically, sawfishes were distributed in the coastal waters of 90 countries and territories. Over the past century, their geographic distribution has been greatly diminished. For example, the smalltooth sawfish is now found in <20% of its former range. Globally, sawfishes are now entirely absent from 20 countries; 43 countries have lost at least one species.
  4. Sawfishes are legally protected, to some degree, in 16 of the 90 range states. These safeguards encompass, on average, 81% of their Extant distribution; however, the quality and breadth of protection varies dramatically across countries and species. Smalltooth sawfish currently has the least amount of such coverage of only half (49%) of Extant distribution.
  5. The global conservation strategy specifies actions to protect sawfish and their habitats. Such actions are urgently warranted to avoid global extinction and to restore robust populations for the benefit of coastal ecosystem function and biodiversity.
© 2014 The Authors. Aquatic Conservation: Marine and Freshwater Ecosystems published by John Wiley & Sons, Ltd.  相似文献   

10.
    
  1. Essential habitats are areas required to support specific functions, such as providing foraging grounds, shelter or used for reproductive purposes. For mobile aquatic species that move throughout numerous components of the seascape, identifying essential habitats within a species' broader distribution range is crucial to understanding their ecology and provide vital information needed to underpin effective conservation and management (e.g. the implementation of protected areas).
  2. In Tasmania (Australia), a number of coastal habitats have been declared shark refuge areas (SRAs), where fishing for elasmobranchs (sharks, rays and skates) is prohibited.
  3. Chimaeras are relatives of elasmobranchs (class Chondrichthyes) and share traits that predispose many elasmobranch species to be vulnerable to overfishing (e.g. slow growth rates and low reproductive output). However, fishing for elephantfish Callorhinchus milii (the chimaera species found in coastal Tasmania) is still permitted in SRAs.
  4. Here, a combination of acoustic tracking, catch data and reproductive information was used to determine the significance of the SRA coastal habitats for C. milii.
  5. Results suggest that these areas are essential habitats for reproduction and likely important for other purposes, such as foraging.
  6. Given that a key strategy in managing fish stocks is protecting areas important for reproduction, and the importance of these coastal areas of Tasmania for C. milii reproductive purposes, we recommend including C. milii in current SRAs, and decreeing these areas as chondrichthyan refuge areas.
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11.
深水网箱养殖中的声学监测问题探讨   总被引：1，自引：0，他引：1  
针对深水网箱养殖过程出现的一些诸如网衣安全、鱼类逃逸等问题,介绍了几种类型的监测技术应用:(1)声学警戒带方式构成的被动式网衣安全监测技术,监视声纳可以是单波束,也可以是机械扫描的多波束或电子扫描的多波束,同时采用水下机器人进行巡视;(2)基于网箱中鱼的目标强度,实现对网箱中养殖品种大小、数量的统计监测,鱼的目标强度主要取决于鱼的体态特征,同时也与发射声波的波长有关;(3)数量识别技术以及饵料投饲过程中的声学监测技术,通过将声纳输出信号反馈到投饵机,实现饵料投放自动化。  相似文献   

12.
    
  1. The Sečovlje salterns on the Northern Adriatic coastline encompass both active and abandoned salt pans on the estuary of the Dragonja River. They are protected as a nature park by a governmental decree and by the Ramsar Convention on Wetlands of International Importance.
  2. In the Sečovlje salterns, salt is still gathered according to a traditional process originating from the 14th century. The high quality of the traditionally produced salt is attributed to a cultivated microbial mat (called ‘petola’) that covers the floor of the crystallization basins and provides a barrier from the anoxic mud. Every spring, in a process called ‘fertilization’, the microbial mat is covered by a layer of mud, a practice that is supposedly crucial for the maintenance of the petola, but its exact role and underlying mechanisms are not yet fully understood.
  3. In early spring 2018 the microbial mat, primarily composed of the filamentous cyanobacterium Coleofasciculus chthonoplastes, was infested by dipteran larvae, which occurred at densities of up to 20,000 m−2. Based on the morphological features of the larvae and imagos, and on DNA analysis of the mitochondrial cytochrome c oxidase subunit I (COI) gene, the newly identified pest was determined to be a chironomid. Under laboratory conditions, larvae fed upon the cyanobacterial mat and destroyed its structure.
  4. In the laboratory, the application of a thin layer of saltern mud in a manner typical for the salt production process prevented the development of chironomid larvae and maintained the structure of the microbial mat. In the salterns, omitting the fertilization step resulted in a considerable weakening of the petola layer.
  5. The results reveal the possible biological background for the fertilization process and thus provides important knowledge for the conservation of the traditional man-made aquatic ecosystem of the Sečovlje salterns.
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13.
    
  1. Surrogates are used in marine conservation planning when there is limited information on the distribution of biodiversity, and representation of species and assemblage diversity are conservation goals. With prior confirmation of their relationship to spatial variation in biodiversity, habitat classification schemes are a potentially useful surrogate.
  2. Polychaetes can comprise over one‐third of species of benthic infaunal assemblages, they are the most frequent and abundant marine metazoans in benthic environments, and they are a reliable surrogate for other macrobenthic taxa.
  3. It was tested whether polychaete biodiversity differed among six estuarine habitat classes defined for conservation planning in the Port Stephens–Great Lakes Marine Park, New South Wales, Australia: subtidal sand, mud, muddy sand, and seagrass beds comprising Posidonia australis, Zostera capricorni and mixed Posidonia/Zostera. Polychaetes were sampled from replicate sites in each habitat and differences among habitat classes in species richness, abundance, and assemblage structure were examined. Several environmental variables, known to be important determinants of polychaete distribution, were also quantified at each site.
  4. Ninety‐five species of polychaetes (belonging to 35 families) were identified. Species richness and abundance did not differ among the habitat classes. Polychaete assemblages of subtidal sand differed from assemblages in both mud and muddy sand, however, assemblages in all other habitats were not different. A combination of some of the measured environmental variables (distance to the estuary entrance, depth, sediment grain size) was a more important determinant of assemblage variation than the habitat classes.
  5. Using these predictors, an alternative habitat classification scheme to the scheme currently utilized in marine park planning is proposed.
  6. This study demonstrates the critical importance of testing assumptions about surrogacy and an approach for refining surrogates.
Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

14.
    
  1. Spatial distribution models (SDMs) have been useful for improving management of species of concern in many areas. This study was designed to model the spatial distribution of bottlenose dolphins among seasons of the year in the Mississippi Sound within the northern Gulf of Mexico.
  2. Models were constructed by integrating presence locations of dolphins acquired from line‐transect sampling from 2011–2013 with maps of environmental conditions for the region to generate a likelihood of dolphin occurrence for winter (January–March), spring (April–June), summer (July–September), and autumn (October–December) using maximum entropy.
  3. Models were successfully generated using the program MaxEnt and had high predictive capacity for all seasons (AUC (area under curve) > 0.8). Distinct seasonal shifts in spatial distribution were evident including increased predicted occurrence in deepwater habitats during the winter, limited predicted occurrence in the western Mississippi Sound in winter and spring, widespread predicted occurrence over the entire region during summer, and a distinct westward shift of predicted occurrence in autumn.
  4. The most important environmental predictors used in SDMs were distance to shore, salinity, and nitrates, but variable importance differed considerably among seasons.
  5. Geographic shifts in predicted occurrence probably reflect both direct effects of changing environmental conditions and subsequent changes in prey availability and foraging efficiency.
  6. Overall, seasonal models helped to identify preferred habitats for dolphins among seasons of the year and can be used to inform management of this protected species in the northern Gulf of Mexico.
Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

15.
    
  1. In the face of environmental degradation, animals with limited plasticity are likely to be the most vulnerable.
  2. Habitat selection by the threatened, endemic Chilean dolphin (Cephalorhynchus eutropia) was investigated in the northern Patagonian fjords, an area of extraordinary biological productivity.
  3. Generalized additive models were undertaken to assess the ecological determinants of Chilean dolphin spatial distribution and habitat selection. Data were collected from dedicated fine‐scale marine surveys conducted during the austral summer of 2007, 2008 and 2009
  4. Modelling techniques provide strong support for Chilean dolphins aggregating in distinct hotspots, preferring shallow water, near rivers and in areas where the influence of tidal regime is greater.
  5. The preference for coastal shallow waters and river influenced habitats by Chilean dolphins puts them in direct conflict with a growing aquaculture industry and hydropower projects. The models predict areas of high densities of Chilean dolphins and excluding these areas from new developments would provide clear protection to the habitat most important to this poorly known endemic Chilean species.
Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

16.
    
  1. A threatened and uncommon soft coral species, Dendronephthya australis found in large abundance in Port Stephens, within the Port Stephens–Great Lakes Marine Park (PSGLMP), New South Wales, Australia, was hypothesized to be an important habitat for many marine fishes and invertebrates, but is currently under threat from boat anchors, fishing debris entanglement and sand inundation.
  2. Surveys were undertaken to assess the biodiversity associated with the soft coral habitat and its adjacent habitats (sponge, seagrass and unvegetated sand), using a combination of Underwater Visual Census (UVC) and Baited Remote Underwater Video System (BRUVS) techniques.
  3. In total, 77 fish species and 21 invertebrate species utilized the D. australis habitat, and multivariate fish assemblages associated with soft corals were significantly different to those associated with nearby sponges, seagrass and sand habitats. Species richness of fishes and invertebrates were significantly higher in soft coral and sponge habitats than seagrass.
  4. The D. australis habitat was found to be of high importance to juvenile snapper (Pagrus auratus: Sparidae), a species of recreational and commercial fishery importance, which occurred in highest abundance within D. australis, and were significantly smaller in size within the soft coral habitat than the adjacent sponge habitat.
  5. Evidently, this rare soft coral habitat supports an extensive marine assemblage, potentially providing a valuable source of food and shelter for fishes and invertebrates, and given it is threatened by human‐induced impacts, its protection should be a priority.
Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

17.
    
  1. Globally, seagrasses and other estuarine habitats are under threat from a range of human disturbances, including boating‐related activities. The fixed, block‐and‐chain swing moorings used to secure boats in many countries can create visible scars in seagrass meadows and remove other benthic organisms.
  2. Losses of seagrasses in two estuaries in New South Wales (NSW), Australia, were quantified using aerial imagery and used to estimate estuarine habitat damage across the remainder of the state. The rate of mooring scar development was approximated and factors influencing the size of mooring scars were identified.
  3. Individually mapped mooring scars in meadows of the endangered Posidonia australis ranged from 55 to 706 m2, and were generally larger than those in the more opportunistic seagrass Zostera muelleri subsp. capricorni (22–342 m2). Scar size in both species of seagrass increased significantly with depth and boat length.
  4. The rate of increase in the size of mooring scars amongst P. australis was roughly linear over 4.8 years, averaging 6.3 m2/month up to a maximum of 16.7 m2/month for one 16‐m yacht.
  5. Across all of NSW, it was estimated that currently leased moorings were causing losses of 129 884 m2 of P. australis and 93 940 m2 of Z. capricorni, and disturbing 2 790 907 m2 of non‐vegetated soft sediments. NSW seagrass loss estimates relate only to damage from current moorings and could be underestimated by ~41% for P. australis if estuaries contain many old scars that remain after the relocation of moorings (as has occurred in Lake Macquarie).
  6. Mandating the use of moorings that do not rely on a chain dragging on the sea bed would greatly reduce future physical damage of benthic habitats and enable some recovery from legacy effects.
  相似文献   

18.
    
  1. Although it is well established that human activities are linked to the loss of seagrasses worldwide, the influence of anthropogenic disturbances on the habitat fragmentation of seagrass meadows is less understood. This information is essential to identify how humans are modifying seascapes and what disturbances pose the greatest risk to seagrasses, which is pertinent given the rapid urbanization occurring in coastal areas.
  2. This study examined how the habitat fragmentation of an endangered seagrass Posidonia australis varied in relation to several anthropogenic disturbances (i.e. human population, marine infrastructure, terrestrial run-off and catchment land-usage) within 10 estuaries across 620 km of coastline in New South Wales, Australia.
  3. When comparing between estuaries, the fragmentation of P. australis meadows was significantly greater in estuaries adjacent to highly populated metropolitan centres – generally in the Greater Sydney region. At sites within estuaries, the density of boat moorings was the most important predictor of habitat fragmentation, but there was also evidence of higher fragmentation with increased numbers of jetties and oyster aquaculture leases.
  4. These results suggest that the fragmentation of seagrass meadows will become more pervasive as the human population continues to grow and estuarine development increases. Strategies to mitigate anthropogenic disturbances on seagrass meadow fragmentation could include prohibiting the construction of boat moorings and other artificial structures in areas where seagrasses are present or promoting environmentally friendly designs for marine infrastructure. This knowledge will support ongoing management actions attempting to balance coastal development and the conservation of seagrasses.
  相似文献   

19.
深水抗风浪网箱监测系统研制方案的探讨   总被引：5，自引：3，他引：5  
探讨一种声学监测方案,用高频、窄脉冲和分裂波束技术,实时监测养殖鱼的进食、生长情况,随时评估网箱内总量的增长情况,并且从水产行业的成本可承受性的实际出发,将成本控制在用户可接受的水平上。  相似文献   

20.
鄱阳湖通江水道是多种洄游性鱼类完成生活史过程的重要通道, 具有重要的生态功能, 对于长江中下游鱼类资源的养护及其多样性维持至关重要。为了解越冬时期鄱阳湖通江水道中不同体长鱼类资源的空间分布规律及栖息生境状况, 本研究将鱼类声学探测、生境遥感定量制图分析和三维水动力模拟相结合, 分别绘制出 3 种不同体长鱼类群落的水深(SID)、流速(SIV)、坡度(SIS)等单因子生境适宜度指数曲线, 并利用乘积法建立栖息地适宜性指数(habitat suitability index, HSI)模型, 对通江水道中不同水域的鱼类生境适宜度进行对比和评估。结果表明, 鄱阳湖通江水道越冬时期鱼类平均全长为(10.1±5.73) cm, 主要分布在屏峰山以北的湖口县、鞋山和屏峰附近 3 个水域; 小体长鱼类群组(1~20 cm)水深的生境适宜度曲线为双峰型, 最适宜水深包括 3.06~4.59 m 和 9.18~12.24 m 两个区间, 流速为 0.05~0.13 m/s, 坡度为 0~2.23°; 中等体长组(20~40 cm)及大体长组(＞40 cm)鱼类适宜的水深、流速和坡度的生境适宜度曲线均为单峰型, 其中中等体长组最适宜栖息的生境因子范围为水深 9.18~13.77 m、流速 0.05~0.13 m/s 和坡度 0~2.23°, 大体长组为 13.77~15.3 m、0.10~0.13 m/s 和 0~2.23°。  相似文献   

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