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1.
The sustained decline in marine fisheries worldwide underscores the need to understand and monitor fisheries trends and fisher behavior. Recreational fisheries are unique in that they are not subject to the typical drivers that influence commercial and artisanal fisheries (e.g., markets or food security). Nevertheless, although exposed to a different set of drivers (i.e., interest or relaxation), recreational fisheries can contribute to fishery declines. Recreational fisheries are also difficult to assess due to an absence of past monitoring and traditional fisheries data. Therefore, we utilized a nontraditional data source (a chronology of spearfishing publications) to document historical trends in recreational spearfishing in Australia between 1952 and 2009. We extracted data on reported fish captures, advertising, and spearfisher commentary and used regression models and ordination analyses to assess historical change. The proportion of coastal fish captures reported declined approximately 80%, whereas the proportion of coral reef and pelagic fish reports increased 1750% and 560%, respectively. Catch composition shifted markedly from coastal temperate or subtropical fishes during the 1950s to 1970s to coral reef and pelagic species in the 1990s to 2000s. Advertising data and commentary by spearfishers indicated that pelagic fish species became desired targets. The mean weight of trophy coral reef fishes also declined significantly over the study period (from approximately 30–8 kg). Recreational fishing presents a highly dynamic social–ecological interface and a challenge for management. Our results emphasize the need for regulatory agencies to work closely with recreational fishing bodies to observe fisher behavior, detect shifts in target species or fishing intensity, and adapt regulatory measures. Tendencias Dinámicas de Captura en la Historia de la Pesca Recreativa con Arpón en Australia 相似文献
2.
Yohei Nakamura 《Marine Biology》2010,157(11):2397-2406
An extensive seagrass bed on a fringing coral reef at Amitori Bay (southern Ryukyu Islands) disappeared completely in 2009
after a typhoon. Seagrass bed loss had a significant negative influence on not only seagrass bed residents but also commercially
important coral reef fishes that utilize seagrass beds as nurseries or feeding grounds. With seagrass bed loss, mean species’
richness and densities of overall seagrass bed fishes per transect decreased by more than 75 and 85%, respectively. Most of
the affected fishes were benthivores, piscivores, detritivores, and herbivores. Of 21 dominant species, 13 disappeared completely
and 4 showed severe reductions in densities following seagrass bed loss, whereas the densities of 4 bottom-dwelling gobies
did not change significantly. Thus, this study demonstrated that most seagrass bed fishes lack the ability to adapt to seagrass
habitat loss, suggesting that increasing global seagrass loss will cause serious reductions in seagrass-associated fishes
and fishery resources. 相似文献
3.
Masakazu Hori Takao Suzuki Yaowaluk Monthum Tippamas Srisombat Yoshiyuki Tanaka Masahiro Nakaoka Hiroshi Mukai 《Marine Biology》2009,156(7):1447-1458
Seagrass species function as typical foundation species that unifies most ecosystem processes. This ecosystem role depends
largely on the morphological characteristics and structural complexity of seagrass beds, including their ecological importance
for fish species. This study examined relationships between seagrass bed characteristics and associated fish communities in
mixed seagrass beds. Correspondence analysis (CA) and canonical correlation analysis (CCoA) were performed to estimate relationships
for individual seagrass bed characteristics. The CCoA results revealed that species richness and three-dimensional structure
of seagrass had great effect on the biomass and richness of the associated fish community. The CA results revealed that the
relative importance of seagrass bed characteristics differed among fish functional groups including fishes appearing on the
surface of, inside, and on the bottom of seagrass beds. The fishes found on the surface of the beds preferred beds with low
seagrass biomass and high three-dimensional structure, those inside the beds preferred beds with high seagrass biomass and
high three-dimensional structure, and those on the bottom of the beds preferred locations with low seagrass biomass and low
three-dimensional structure. The results of this study provide compelling evidence that seagrass beds with high species diversity
and high three-dimensional structure, but intermediate biomass, may provide the great benefit to the associated fish community.
Such niche complementarity among fishes may be a process facilitated by seagrass diversity for secondary production as an
ecosystem functioning. 相似文献
4.
Seagrass beds are highly productive ecosystems and a decline in this habitat has become a global concern in recent decades. This study mapped seagrass at three sites in Port Phillip Bay between 1939 and 2011 and reviewed possible influences on seagrass cover changes. Historical aerial photographs from multiple sources were digitally scanned and orthorectified. Automated image processing techniques incorporating an unsupervised classification combined with minor editing in a GIS were applied to map seagrass cover and analyse variations in the size and distribution of seagrass beds. Large declines in seagrass cover were observed at all three sites after 1998. In contrast to other world-wide observations, these recent declines were preceded by a period of sustained seagrass expansion between the 1960s and 1990s and lower levels of seagrass cover were observed in the 1930s/40s. The recent and earlier low levels of seagrass cover coincided with extended droughts characterised by large reductions in nutrient inputs to the Bay. However, recent declines were not consistent across the Bay with three other sites remaining relatively stable during this period. The sites with large declines are all subject to longshore drift and changes in nearshore sediment transport driven by variations in weather patterns coinciding with extended periods of drought may be important influences on seagrass cover at these locations. 相似文献
5.
Mangrove forests and seagrass beds frequently occur as adjacent habitats in the temperate waters of southeastern Australia.
At low tide when fish cannot occupy mangroves they might utilise adjacent habitats, including seagrass. We first sampled small
fish from seagrass beds close to and far from mangroves in the Pittwater estuary, NSW, Australia. Seagrass beds close to mangroves
had a greater density of fish species than beds far from mangroves (close: mean 16.0 species net−1, SE 1.0; far: 13.2, 1.3; P < 0.05). In particular, juvenile fish were in greater densities near to than far from mangroves (close: 5.3, 0.4; far: 3.1,
0.4; P < 0.05). We then sampled the mangrove forests during the high tide and seagrass beds during the low tide, in beds along a
continuum of distances from mangroves. Multivariate analysis showed that fish assemblages differed with distance from mangroves,
and the differences were attributed to the composition of the fish assemblage (i.e. presence/absence of fish species), not
the abundances of individual species. In particular, fish that utilise mangrove forests at high tide were found in greater
species densities and species richness in seagrass nearer to mangroves. A negative relationship was found between the density
of mangrove-utilising fish species and the distance of the bed from mangroves (R
2 = 0.37, P < 0.05). This confirms the important connectivity between mangroves and seagrass for fish in temperate Australian waters. 相似文献
6.
HEIDI GJERTSEN DALE SQUIRES PETER H. DUTTON TOMOHARU EGUCHI 《Conservation biology》2014,28(1):140-149
Although holistic conservation addressing all sources of mortality for endangered species or stocks is the preferred conservation strategy, limited budgets require a criterion to prioritize conservation investments. We compared the cost‐effectiveness of nesting site and at‐sea conservation strategies for Pacific leatherback turtles (Dermochelys coriacea). We sought to determine which conservation strategy or mix of strategies would produce the largest increase in population growth rate per dollar. Alternative strategies included protection of nesters and their eggs at nesting beaches in Indonesia, gear changes, effort restrictions, and caps on turtle takes in the Hawaiian (U.S.A.) longline swordfish fishery, and temporal and area closures in the California (U.S.A.) drift gill net fishery. We used a population model with a biological metric to measure the effects of conservation alternatives. We normalized all effects by cost to prioritize those strategies with the greatest biological effect relative to its economic cost. We used Monte Carlo simulation to address uncertainty in the main variables and to calculate probability distributions for cost‐effectiveness measures. Nesting beach protection was the most cost‐effective means of achieving increases in leatherback populations. This result creates the possibility of noncompensatory bycatch mitigation, where high‐bycatch fisheries invest in protecting nesting beaches. An example of this practice is U.S. processors of longline tuna and California drift gill net fishers that tax themselves to finance low‐cost nesting site protection. Under certain conditions, fisheries interventions, such as technologies that reduce leatherback bycatch without substantially decreasing target species catch, can be cost‐effective. Reducing bycatch in coastal areas where bycatch is high, particularly adjacent to nesting beaches, may be cost‐effective, particularly, if fisheries in the area are small and of little commercial value. Rentabilidad de Estrategias de Conservación Alternativas Aplicadas a Tortugas Laúd del Pacífico 相似文献
7.
R. S. STENECK T. P. HUGHES J. E. CINNER W. N. ADGER S. N. ARNOLD F. BERKES S. A. BOUDREAU K. BROWN C. FOLKE L. GUNDERSON P. OLSSON M. SCHEFFER E. STEPHENSON B. WALKER J. WILSON B. WORM 《Conservation biology》2011,25(5):904-912
Abstract: Unsustainable fishing simplifies food chains and, as with aquaculture, can result in reliance on a few economically valuable species. This lack of diversity may increase risks of ecological and economic disruptions. Centuries of intense fishing have extirpated most apex predators in the Gulf of Maine (United States and Canada), effectively creating an American lobster (Homarus americanus) monoculture. Over the past 20 years, the economic diversity of marine resources harvested in Maine has declined by almost 70%. Today, over 80% of the value of Maine's fish and seafood landings is from highly abundant lobsters. Inflation‐corrected income from lobsters in Maine has steadily increased by nearly 400% since 1985. Fisheries managers, policy makers, and fishers view this as a success. However, such lucrative monocultures increase the social and ecological consequences of future declines in lobsters. In southern New England, disease and stresses related to increases in ocean temperature resulted in more than a 70% decline in lobster abundance, prompting managers to propose closing that fishery. A similar collapse in Maine could fundamentally disrupt the social and economic foundation of its coast. We suggest the current success of Maine's lobster fishery is a gilded trap. Gilded traps are a type of social trap in which collective actions resulting from economically attractive opportunities outweigh concerns over associated social and ecological risks or consequences. Large financial gain creates a strong reinforcing feedback that deepens the trap. Avoiding or escaping gilded traps requires managing for increased biological and economic diversity. This is difficult to do prior to a crisis while financial incentives for maintaining the status quo are large. The long‐term challenge is to shift fisheries management away from single species toward integrated social‐ecological approaches that diversify local ecosystems, societies, and economies. 相似文献
8.
A good understanding of social factors that lead to marine ecological change is important to developing sustainable global fisheries. We used balanced panel models and conducted cross‐national time‐series analyses (1970–2010) of 122 nations to examine how economic prosperity and population growth affected the sustainability of marine ecosystems. We used catches in economic exclusive zone (EEZ); mean trophic level of fishery landings (MTL); primary production required to sustain catches (expressed as percentage of local primary production [%PPR]); and an index of ecosystem overfishing (i.e., the loss in secondary production index [L index]) as indicators of ecological change in marine ecosystems. The EEZ catch, %PPR, and L index declined gradually after gross domestic product (GDP) per capita reached $15,000, $14,000, and $19,000, respectively, and MTL increased steadily once GDP per capita exceeded $20,000. These relationships suggest that economic growth and biodiversity conservation are compatible goals. However, increasing human populations would degrade marine ecosystems. Specifically, a doubling of human population caused an increase in the %PPR of 17.1% and in the L index of 0.0254 and a decline in the MTL of 0.176. A 1% increase in human population resulted in a 0.744% increase in EEZ catch. These results highlight the importance of considering social and economic factors in developing sustainable fisheries management policy. 相似文献
9.
Fishing pots (i.e., traps) are designed to catch fish or crustaceans and are used globally. Lost pots are a concern for a variety of fisheries, and there are reports that 10 – 70% of deployed pots are lost annually. Derelict fishing pots can be a source of mortality for target and bycatch species for several years. Because continual removal of derelict gear can be impractical over large spatial extents, modifications are needed to disarm gear once it is lost. We tested a fully biodegradable panel with a cull or escape ring designed for placement on the sides of a crab pot that completely degrades into environmentally neutral constituents after approximately 1 year. This panel is relatively inexpensive, easy to install, and can be used in multiple fisheries. We used the blue crab (Callinectes sapidus) fishery as a test case because it is a large pot fishery and blue crab pots are similar to traps used in other pot fisheries. We had commercial fishers deploy pots with panels alongside standard pots in Chesapeake Bay (U.S.A.) to assess potential effects of our experimental pots on blue crab catch. We compared the number, biomass, and size of crabs captured between standard and experimental pots and evaluated differences in catch over a crabbing season (March–November) at five locations. There was no evidence that biodegradable panels adversely affected catch. In all locations and time periods, legal catches were comparable in abundance, biomass, and size between experimental and standard pots. Properly designed biodegradable panels appear to be a viable solution to mitigate adverse effects of derelict pots. Uso de Paneles Completamente Biodegradables para Reducir las Amenazas de Vasijas Abandonadas para la Fauna Marina 相似文献
10.
Elisa Alonso Aller Martin Gullström Floriaan K J Eveleens Maarse Michaela Gren Lina Mtwana Nordlund Narriman Jiddawi Johan S. Eklöf 《Marine Biology》2014,161(10):2395-2405
Seagrass beds are highly important for tropical ecosystems by supporting abundant and diverse fish assemblages that form the basis for artisanal fisheries. Although a number of local- and regional-scale variables are known to influence the abundance, diversity and assemblage structure of seagrass-associated fish assemblages, few studies have evaluated the relative and joint (interacting) influences of variables, especially those acting at different scales. Here, we examined the relative importance of local- and regional-scale factors structuring seagrass-associated fish assemblages, using a field survey in six seagrass (Thalassodendron ciliatum) areas around Unguja Island (Zanzibar, Tanzania). Fish density and assemblage structure were mostly affected by two regional-scale variables; distance to coral reefs, which positively affected fish density, and level of human development, which negatively affected fish density. On the local scale, seagrass biomass had a positive (but weaker) influence on fish density. However, the positive effect of seagrass biomass decreased with increasing level of human development. In summary, our results highlight the importance of assessing how multiple local and regional variables, alone and together, influence fish communities, in order to improve management of seagrass ecosystems and their services. 相似文献
11.
James Nelson Rachel Wilson Felicia Coleman Christopher Koenig Doug DeVries Chris Gardner Jeff Chanton 《Marine Biology》2012,159(2):365-372
Seagrass meadows are among the most productive ecosystems in the marine environment. It has been speculated that much of this
production is exported to adjacent ecosystems via the movements of organisms. Our study utilized stable isotopes to track
seagrass-derived production into offshore food webs in the northeastern Gulf of Mexico. We found that gag grouper (Myctereoperca microlepis) on reefs as far as 90 km from the seagrass beds incorporate a significant portion of seagrass-derived biomass. The muscle
tissue of gag grouper, a major fisheries species, was composed on average of 18.5–25% seagrass habitat-derived biomass. The
timing of this annual seagrass subsidy appears to be important in fueling gag grouper egg production. The δ34S values of gag grouper gonad tissues varied seasonally and were δ34S depleted during the spawning season indicating that gag utilize the seagrass-derived biomass to support reproduction. If
such large scale trophic subsidies are typical of temperate seagrass systems, then loss of seagrass production or habitat
would result in a direct loss of offshore fisheries productivity. 相似文献
12.
MARY GLEASON ERIKA M. FELLER MATT MERRIFIELD STEPHEN COPPS ROD FUJITA MICHAEL BELL STEVE RIENECKE CHUCK COOK 《Conservation biology》2013,27(3):470-479
Private‐sector financial and legal transactions have long been used to protect terrestrial habitats and working landscapes, but less commonly to address critical threats in marine environments. Transferrable and marketable fishing privileges, including permits and quotas, make it possible to use private‐sector transactions as conservation strategies to address some fishery management issues. Abating the effects of bottom trawling on the seafloor and bycatch and discard associated with the practice has proven challenging. On the Central Coast of California, The Nature Conservancy (TNC), Environmental Defense Fund, local fishers and local, state, and federal authorities worked collaboratively to protect large areas of the seafloor from bottom trawling for groundfish while addressing economic impacts of trawl closures. Contingent on the adoption of trawl‐closure areas by a federal regulatory agency, TNC used private funds to purchase federal groundfish trawl permits and vessels from willing sellers. Trawl‐closure areas were designed collaboratively by combining regional biological diversity and fisheries data with local fishers’ knowledge. The private transactional strategy was designed to remedy some deficiencies in previous federal buyouts, to mitigate economic impacts from trawl closures, and to carefully align with a public regulatory process to protect “essential fish habitat” under the Magnuson‐Stevens Fishery Conservation and Management Act. This collaborative effort protected 1.5 million ha (3.8 million acres) of seafloor, reduced trawl effort in the area by 50%, and set a precedent for collaborative partnerships between conservation and fishing interests. This is the first time a large conservation organization has taken an ownership position in a fishery and demonstrates how nongovernmental organizations can invest in fisheries to improve environmental and economic performance. Un Método Transaccional y Colaborativo para Reducir los Efectos de la Pesca de Arrastre de Fondo 相似文献
13.
Joshua K. Abbott James E. Wilen 《Journal of Environmental Economics and Management》2009,58(3):300-314
Recreational fisheries are increasingly important in fisheries management; for some species, recreational take rivals or exceeds the amount harvested by commercial fishermen. Most recreational fisheries are regulated with gear restrictions, bag limits, and time/area closures, but there is increasing interest in the market-based solutions employed in commercial fisheries — this despite the lack of an adequate bioeconomic theory of the joint commercial/recreational aspects of many recreational fisheries. This paper integrates a detailed production specification with traditional bioeconomic tools in order to better understand the implications of rationalization schemes targeted at the charter sector. While confirming some of the qualitative conclusions of the commercial fisheries literature on open access and regulated open access our model also generates rich and novel predictions with respect to input choices, the number of vessels and congestion externalities. We devise a system of instruments that generate efficient outcomes and extensively discuss issues associated with their real-world implementation. 相似文献
14.
Seagrass beds are often considered to be important nurseries for coral reef fish, yet the effectiveness of these nursery functions
(refuge and food availability) at different juvenile stages is poorly understood. To understand how the demands of juvenile
fish on seagrass nursery functions determines the timing of ontogenetic habitat shifts from seagrass beds to coral reefs,
we conducted visual transect survey and field tethering and caging experiments on three different sizes of the coral reef
fish Pacific yellowtail emperor (Lethrinus atkinsoni) during its juvenile tenure in seagrass beds at Ishigaki Island, southern Japan. The study showed that although the number
of individual L. atkinsoni juveniles decreased by >90 % during their stay in the seagrass nursery, the shelter and/or food availability functions of
the nursery, at least for a juvenile size of approximately 5 cm total length (TL), provided the best survival and growth option.
The timing of ontogenetic migration to coral reefs of larger fish (>8 cm TL) was attributed to foraging efficiency for larger
food items in different habitats. Overall, the function of the seagrass bed nursery changed with juvenile body size, with
marginally higher survival and significantly greater growth rates during early juvenile stages in seagrass beds compared to
coral reefs. This would contribute to the enhancement in the number of individuals eventually recruited to adult populations. 相似文献
15.
Anna-Maria Vafeiadou Patrick Materatski Helena Adão Marleen De Troch Tom Moens 《Marine Biology》2013,160(9):2517-2523
Stable carbon and nitrogen isotope analysis was used to examine the resources and position of macrobenthos in an estuarine seagrass food web in two sampling moments, during summer and winter. The contribution of each food source to the carbon requirements of consumers was estimated by a mixing model. The used carbon sources were largely seagrass associated, although seagrass tissues were utilized by only few species, and equally contributed to microphytobenthos and suspended particulate organic matter. Based on isotopic data, Lucinidae bivalves have an alternative trophic pathway via symbiosis with chemoautotrophic bacteria. Resource utilization inside and adjacent to seagrass beds did not differ significantly, implying that seagrass-associated inputs extend well beyond the borders of the vegetation patches. 相似文献
16.
Nutrient resorption from seagrass leaves 总被引:4,自引:0,他引:4
The resorption of nutrients (C, N and P) from senescent leaves of six seagrass species from nine different locations in tropical
(Indonesia and Kenya), Mediterranean (Spain) and temperate (The Netherlands) regions has been investigated. Resorption was
quantitatively assessed by calculating the difference in nutrient content between the leaves with the highest content, and
the oldest leaves. In order to do so, the leaves were classified according to their age. The nutrient contents of leaves of
a given age category were calculated by multiplying the measured nutrient concentration in this age category with its corresponding
modelled leaf biomass. N- and P-concentrations declined during ageing and senescence of the leaves in all of the investigated
situations but two. The decline in concentration varied up to 58% for N and up to 66% for P. The C-concentration declined
on three of the investigated occasions and varied up to 24%. Despite a decline in concentration, the leaf C-content did not
change, indicating no resorption of carbon. The efficiency of N-resorption from intact seagrass leaves varied between 3.8
and 29% (average: 15%), while the efficiency of phosphorus resorption varied between 0 and 51% (average: 21%). The resorption
efficiency was not significantly different in seagrasses with a relatively high and a relatively low nutrient concentration,
although within-species comparisons showed that in some cases resorption efficiency was positively related to the nutrient
concentration of the leaves. Premature loss of leaves and leaf fragments (by e.g. herbivory) may substantially interfere with
the resorption process. In Indonesian seagrasses we estimated that as a result of fragmentation and premature detachment only
between 56 and 77% of the physiological resorption potential actually was realised. It is concluded that internal resorption
may play a role in the nutrient dynamics of seagrass plants, but that its quantitative importance probably is limited. Nutrient
resorption from senescent seagrass leaves may reduce the nutrient requirements for seagrass leaf production by approximately
10% for nitrogen and 15% for phosphorus.
Received: 28 September 1996 / Accepted: 7 November 1996 相似文献
17.
Effects of surrounding land use and water depth on seagrass dynamics relative to a catastrophic algal bloom 下载免费PDF全文
Seagrasses are the foundation of many coastal ecosystems and are in global decline because of anthropogenic impacts. For the Indian River Lagoon (Florida, U.S.A.), we developed competing multistate statistical models to quantify how environmental factors (surrounding land use, water depth, and time [year]) influenced the variability of seagrass state dynamics from 2003 to 2014 while accounting for time‐specific detection probabilities that quantified our ability to determine seagrass state at particular locations and times. We classified seagrass states (presence or absence) at 764 points with geographic information system maps for years when seagrass maps were available and with aerial photographs when seagrass maps were not available. We used 4 categories (all conservation, mostly conservation, mostly urban, urban) to describe surrounding land use within sections of lagoonal waters, usually demarcated by land features that constricted these waters. The best models predicted that surrounding land use, depth, and year would affect transition and detection probabilities. Sections of the lagoon bordered by urban areas had the least stable seagrass beds and lowest detection probabilities, especially after a catastrophic seagrass die‐off linked to an algal bloom. Sections of the lagoon bordered by conservation lands had the most stable seagrass beds, which supports watershed conservation efforts. Our results show that a multistate approach can empirically estimate state‐transition probabilities as functions of environmental factors while accounting for state‐dependent differences in seagrass detection probabilities as part of the overall statistical inference procedure. 相似文献
18.
ASTRID J. SCHOLZ CHARLES STEINBACK SARAH A. KRUSE MIKE MERTENS HOWARD SILVERMAN 《Conservation biology》2011,25(3):485-492
Abstract: Social, economic, and ecological criteria contribute to the successful design, implementation, and management of marine protected areas (MPAs). In the context of California's Marine Life Protection Act Initiative, we developed a set of methods for collecting, compiling, and analyzing data about the spatial extent and relative economic importance of commercial and recreational fishing. We interviewed 174 commercial fishers who represented the major fisheries in the initiative's north‐central coast region, which extends from Point Arena south to Pigeon Point. These fishers provided data that we used to map the extent of each of the fishing grounds, to weight the relative importance of areas within the grounds, to characterize the operating costs of each fishery, and to analyze the potential economic losses associated with proposed marine protected areas. A regional stakeholder group used the maps and impact analyses in conjunction with other data sets to iteratively identify economic and ecological trade‐offs in designations of different areas as MPAs at regional, port, and fishery extents. Their final proposed MPA network designated 20% of state waters as MPAs. Potential net economic loss ranged from 1.7% to 14.2% in the first round of network design and totaled 6.3% in the final round of design. This process is a case study in the application of spatial analysis to validate and integrate local stakeholder knowledge in marine planning. 相似文献
19.
Penaeid prawns were sampled with a small seine net to test whether catches of postlarvae and juveniles in seagrass were affected by the distance of the seagrass (mainly Zostera capricorni) from mangroves and the density of the seagrass in a subtropical marine embayment. Sampling was replicated on the western and eastern sides of Moreton Bay, Queensland, Australia. Information on catches was combined with broad-scale spatial information on the distribution of habitats to estimate the contribution of four different categories of habitat (proximal dense seagrass, distal dense seagrass, proximal sparse seagrass, distal sparse seagrass) to the overall population of small prawns in these regions of Moreton Bay. The abundance of Penaeus plebejus and Metapenaeus bennettae was significantly and consistently greater in dense seagrass proximal to mangroves than in other types of habitat. Additionally, sparse seagrass close to mangroves supported more of these species than dense seagrass farther away, indicating that the role of spatial arrangement of habitats was more important than the effects of structural complexity alone. In contrast, the abundance of P. esculentus tended to be greatest in sparse seagrass distal from mangroves compared with the other habitats. The scaling up of the results from different seagrass types suggests that proximal seagrass beds on both sides of Moreton Bay provide by far the greatest contribution of juvenile M. bennettae and P. plebejus to the overall populations in the Bay.Communicated by M.S. Johnson, Crawley 相似文献
20.
Hawksbill sea turtles, Eretmochelys imbricata, are closely associated with coral reef and other hard-bottom habitats. Seagrass pastures are peripheral habitats for Caribbean
hawksbills. With the decline in quality and quantity of coral reefs, seagrass habitats may become more important for hawksbills.
We use data from a 30-year mark-recapture study of hawksbills and green turtles, Chelonia mydas, in the southern Bahamas to assess the quality of a seagrass habitat for hawksbills. Size distribution, residence times,
and body condition index for the seagrass hawksbill aggregation are similar to those of hawksbill aggregations over Caribbean
reefs. Somatic growth rates of seagrass hawksbills are in the upper range of those reported for reef hawksbills. Based on
these parameters, peripheral seagrass habitats can support healthy, productive hawksbill aggregations. During the 30-year
study, a sixfold variation in green turtle density in the study area did not affect the productivity or body condition of
hawksbills. 相似文献