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1.
Synopsis Herbivorous fishes and invertebrates are conspicious elements of coral reef communities where they predominate both in numbers and biomass. Herbivores and the coral reef algae on which they feed represent a co-evolved system of defense and counter-defense. Algal species have developed toxic, structural, spatial and temporal defense or escape mechanisms, while the herbivores employ strategies that involve anatomical, physiological and behavioral adaptations. Current research demonstrates that many reef fishes are highly selective in the algae they consume. Food selection in these fishes may be correlated with their morphological and digestive capabilities to rupture algal cell walls. Sea urchins select more in accordance with relative abundance, although certain algal species are clearly avoided.The determinants of community structure on coral reefs have yet to be established but evidence indicates a strong influence by herbivores. Reef herbivores may reduce the abundance of certain competitively superior algae, thus allowing corals and cementing coralline algae to survive. We discuss how the foraging activities of tropical marine herbivores affect the distribution and abundance of algae and how these activities contribute to the development of coral reef structure and the fish assemblages which are intimately associated with reef structure.This paper forms a part of the proceedings of a mini-symposium convened at Cornell University, Ithaca, N.Y., 18–19 May 1976, entitled Patterns of Community Structure in Fishes (G. S. Helfman, ed.).  相似文献   

2.
The use of artificial reefs in enhancing fish communities in Singapore   总被引:1,自引:0,他引:1  
Intense development of the coastal zone in Singapore has resulted in the degradation of much of the marine ecosystem. In order to restore and enhance fish communities of denuded areas, an artificial reef consisting of a tyre reef and a concrete reef, was established in the vicinity of the southern islands of Singapore. Results from fish visual censuses after the establishment of the artificial reef indicated an increase in numbers of juveniles and adults. A total of 37 and 32 fish species were recorded over a period of 1/2 years at the concrete and tyre reefs respectively. The dominant fish families were Pomacentridae, Labridae, Chaetodontidae, Apogonidae, Gobiidae and Nemipteridae. The artificial reefs also serve as a nursery ground for some species (e.g. Neopomacentrus sp.) which are important primary consumers of algae on natural reefs. Greater numbers of target (food-important) fishes were observed at the concrete reef while the tyre reef harboured more juveniles and smallersized adults. The results indicate that the concrete modules were more effective than the tyre reef in terms of fish abundance per unit volume. Such structures can enhance the biological resources of relatively unproductive areas.  相似文献   

3.
Coral-dwelling fishes from the genus Gobiodon are some of the most habitat specialised fishes on coral reefs. Consequently, we might expect that their population dynamics will be closely associated with the abundance of host corals. I used a combination of log-linear modelling and resource selection ratios to examine patterns of habitat use among eight species of Gobiodon in Kimbe Bay, Papua New Guinea. I then used multiple regression analysis to investigate relationships between the abundance of each species of Gobiodon and the abundance of the corals they inhabited. Each species of Gobiodon used one or more species of coral more frequently than expected by chance. The pattern of habitat use exhibited by each species of Gobiodon did not vary among reef zones or among reefs with different exposures to prevailing winds, despite changes in the relative abundances of corals among reef zones. This consistency in habitat use might be expected if the coral species inhabited confer considerable fitness advantages and, therefore, are strongly preferred. For most species of Gobiodon, abundances among reef zones and exposure regimes were correlated with the abundance of the coral species usually inhabited. Therefore, it appears that habitat availability helps determine abundances of most species of Gobiodon in Kimbe Bay. In addition to correlations with habitat availability, the abundances of G. histrio, G. quinquestrigatus, G. rivulatus (dark form) and the group others were also associated with particular reef zones and exposure regimes. Therefore, in these species, reef type appears to influence patterns of abundance independently of coral availability. In contrast to other species of Gobiodon, the abundance of the most specialised species, Gobiodon sp.A, was not closely associated with the abundance of the only coral species it inhabited. This study demonstrates that even for habitat specialised species, the relationship between habitat availability and abundance varies widely and is multiscale.  相似文献   

4.
Synopsis Data are summarised from studies of two reef fish communities — pomacentrids territorial on rubble patches, and fishes resident in small isolated colonies of coral. In each case there is evidence that availability of living sites limits numbers of fishes, and that similar species of fish use the same kinds of spaces. Priority of arrival as recruits, rather than subtle differences in requirements or competitive abilities of adults, appears to determine which species holds each site. Faced with a limited and patchy supply of living space, most reef fishes are sedentary as adults, and produce frequent clutches of pelagic larvae over extended breeding seasons In this way they maximise their chances of getting offspring into suitable living sites as such sites appear. It is argued that by adopting this strategy, reef fishes are preadapted for forming inter-specific lotteries for living space if several species with similar requirements occur together. Such lotteries among similar species may be a feature common to many reef fish communities, and may explain the typically high within-site diversity found in them.This paper forms part of the proceedings of a mini-symposium convened at Cornell University, Ithaca, N.Y., 18–19 May 1976, entitled Patterns of Community Structure in Fishes (G. S. Helfman, ed.).  相似文献   

5.
We report on the lens pigmentation and visual pigments of 52 species of demersal deep-sea fishes caught at depths ranging from 480 m to 4110 m in the Porcupine Seabight and Goban Spur area of the North-eastern Atlantic. Only one species, caught between 480 and 840 m, had a lens with large amounts of pigment, consistent with the hypothesis that heavily pigmented lenses in deep-sea fish serve to enhance the contrast of bioluminescent signals by removing much of the background radiance, which is only visible to fish living shallower than 1000 m. Low concentrations of lens pigmentation were also observed in a further two species (Rouleina attrita and Micromesisteus poutassou). The retinae of all species except five, contained only a single visual pigment, as determined by microspectrophotometry of individual rods, and/or spectrophotometry of retinal wholemounts and retinal extracts. Those fishes caught between 500 m and 1100 m had wavelengths of peak sensitivity (max) ranging from 476 nm to 494 nm, while most fish living below 1100 m tended to be more conservative with (max) values ranging from 475 nm to 485 nm. The only exceptions to this were three deep-living species caught between 1600 m and 2000 m whose retinae contain abnormally short-wave sensitive visual pigments (Cataetyx laticepsmax 468 nm; Alepocephalus bairdiimax 467 nm; Narcetes stomias max 472 nm), suggesting adaptation for the detection of short-wave bioluminescence.  相似文献   

6.
Summary The inheritance of two mutants of flax (Linum usitatissimum), having altered proportions of the C18 polyunsaturated fatty acids, linoleic and linolenic, was examined. Both lines, M1589 and M1722, are homozygous for a single gene mutation which reduces linolenic acid content from 34% to 22% and raises linoleic acid from 15% to 27%. Genetic analysis of crosses involving M1589, M1722 and their parental cultivar Glenelg revealed that these mutations are in different unlinked genes and exhibit additive (codominant) gene action. The symbolsLn1 andLn2 are proposed for the mutated genes in M1589 and M1722, respectively. Recombinant genotypes homozygous for the mutant alleles at both loci are very low in linolenic acid (2%) and high in linoleic acid (48%), with unaltered proportions of other fatty acids. The complete inverse correlation between linoleic and linolenic acids (r=-0.98) indicates that the mutations block the synthesis of linolenic acid at the linoleic desaturation step.  相似文献   

7.
Middleton and Elizabeth Reefs are two mid-latitude, annular reefs within the Lord Howe linear chain of volcanic islands and seamounts in the southwestern Pacific Ocean. Drilling, vibrocoring, seismic profiling, and dating indicate that each has a rim of Holocene reef framework, enclosing a lagoon partly filled by prograding sand sheets composed of fragments of coral, coralline algae, foraminifers, and other skeletal debris. The reefs lie close to the latitudinal limits for coral growth and the reef framework is very porous, dominated by branching rather than massive corals. Coralline algae are the principal binding agent in the upper reef framework. Holocene reef growth began on a foundation of Pleistocene reefal limestone encountered at a depth of 8 m in cores on the windward side of Middleton Reef. Holocene corals became established on this foundation around 6,700 radiocarbon yr B.P., implying little if any lag after inundation of the platform by the post-glacial sea-level rise. Windward reef growth tracked sea-level rise (keep-up mode), and a prominent reef crest was established on both reefs by 5,000 yr B.P. Leeward margins appear to have been characterized by catch-up growth. Development of cays is limited, and has been restricted by the paucity of coarse coralline debris or cemented conglomerate on which islands could become established. The morphology and development of Middleton and Elizabeth Reefs has been similar to that of tropical atolls, although the rate of subsidence appears to have been relatively slow reflecting their position on the margin of the foundered continental crust of the Lord Howe Rise.  相似文献   

8.
The influence of n-propanol on the overall -helical conformation of -globin, apocytochrome C, and the functional domain of streptococcal M49 protein (pepM49) and its consequence on the proteolysis of the respective proteins has been investigated. A significant amount of -helical conformation is induced into these proteins atpH 6.0 and 4°C in the presence of relatively low concentrations of n-propanol. The induction of -helical conformation into the proteins increased as a function of the propanol concentration, the maximum induction occurring around 30% n-propanol. In the case of -globin, the fluorescence of its tryptophyl residues also increased as a function of n-propanol concentration, the midpoint of this transition being around 20% n-propanol. Furthermore, concomitant with the induction of helical conformation into these proteins, the proteolysis of their polypeptide chain by V8 protease also gets restricted. The -helical conformation induced into - and -globin by n-propanol decreased as the temperature is raised from 4 to 24°C. In contrast, the -helical conformation of both - and -chain (i.e., globin with noncovalently bound heme) did not exhibit such a sensitivity to this change in temperature. However, distinct differences exist between the n-propanol induced -helical conformation of globins and the -helical conformation of - and -chains. A cross-correlation of the n-propanol induced increase in the fluorescence of -globin with the corresponding increase in the -helical conformation of the polypeptide chain suggested that the fluorescence increase represents a structural change of the protein that is secondary to the induction of the -helical conformation into the protein (i.e., an integration of the helical conformation induced to the segments of the polypeptide chain to influence the microenvironment of the tryptophyl residues). Presumably, the fluorescence increase is a consequence of the packing of the helical segments of globin to generate a native-like structure. The induction of -helical conformation into these proteins in the presence of n-propanol and the consequent generation of native-like conformation is not unique to n-propanol. Trifluoroethanol, another helix-inducing organic solvent, also behaves in the same fashion as n-propanol. However, in contrast to the proteins described above, n-propanol could neither induce an -helical conformation into performic acid oxidized RNAse-A nor restrict its proteolysis by proteases. Thus, the high sensitivity of apoproteins and the protein domains to assume -helical conformation in the presence of low concentration of n-propanol with a concomitant restriction of the proteolytic susceptibility of their polypeptide chain appears to be unique to those proteins that exhibit high -helical propensities. Apparently, this phenomenon of helix induction and the restriction of proteolysis reflects the formation of rudimentary tertiary interaction of the native protein and is unique to apoproteins or structural domains of -helical proteins. Consistent with this concept, the induction of -helical conformation into shorter polypeptide fragments of 30 residues, (e.g., 1-30, which exists in an -helical conformation in hemoglobin) is very low. Besides, this peptide exhibited neither the high sensitivity to the low concentrations of n-propanol seen with the apoproteins/protein domains nor the resistance toward proteolysis. The results suggest that the organic cosolvent induced decrease in the conformational flexibility of the apoprotein, and the consequent restriction of their proteolytic cleavage provides an opportunity to develop new strategies for protease catalyzed segment condensation reactions.  相似文献   

9.
The two-phase life history of most marine fishes and invertebrates has enormous implications for dispersal, population connectivity, and resource management. Pelagic dispersal larvae of marine animals traditionally thought to ensure that populations are widespread, that chances of local extinction are low, and that marine protected areas (MPA) can easily function to replenish both their own populations and those of unprotected areas. Traditionally, dispersal is considered to depend primarily on two variables: pelagic larva duration and far-field currents. These conclusions arise from the open population paradigm and are usually accompanied by a simplifying assumption: larvae are distributed passively by far-field currents. Unfortunately, they ignore the complex reality of circulation and hydrological connectivity of reefs, and do not consider newly-demonstrated behavioural capabilities of coral-reef fish larvae. Far-field circulation varies with depth and often excludes water bodies where propagules are released, and this has important implications for predicting trajectories of even passive larvae. However, larvae are not passive: late-stage larvae of coral-reef fishes can swim faster than currents for long periods, can probably detect reefs at some distance, and can actively find them. This behaviour is flexible, which greatly complicates modelling of larval fish trajectories. Populations at ecological (as opposed to evolutionary) scales are probably less open and more subdivided than previously assumed. All this means that dispersal predictions based solely on far-field water circulation are probably wrong. An emerging view of larval-fish dispersal is articulated that takes these new data and perspectives into account. This emerging view shows that re-evaluation of traditional views in several areas is required, including the contribution of larval-fish biology and dispersal to biodiversity patterns, the way reef fishes are managed, and the way in which MPA are thought to operate. At evolutionary and zoogeographic scales, reef-fish populations are best considered to be open.  相似文献   

10.
Synopsis Predation on 120 adult sea urchins of the speciesEchinometra mathaei was observed during daylight in shallow-water coral reefs (0.5 to 3 m deep) in a variety of sites in 3 Kenyan marine parks. The predators were few (8 species) and dominated by the triggerfishBalistapus undulatus (65 % of all observations) followed by terminal-male wrassesCoris formosa, C. aygula andCheilinus trilobatus, and lastly the scavengerLethrinus mahsena. Those species that attempted, but failed, to prey onE. mathaei were slightly more numerous (11 species), while scavengers of opened carcasses were the most speciose (20 species). Based on these observations, it is suggested thatB. undulatus is a keystone predator and that fishery regulations that protect this species may be necessary in order to reduce the detrimental consequences of high sea urchin abundance — such as high reef substrate erosion and competitive exclusion of fishes.  相似文献   

11.
A massive Porites microatoll generally has three types of microhabitat at the top, side, and base of the microatoll. The purpose of the present study was to analyze microhabitat associations of reef fish on microatolls to determine whether habitat characteristics play an important role in the structuring of reef fish assemblages in a patchy habitat. We also investigated temporal stability of reef fish assemblage structures over a period of 17 months to determine whether fish assemblage structures vary in a random manner. The results of correspondence analysis indicated species-specific habitat associations for pomacentrids (five species) and labrids (seven species). The degree of temporal stability of fish assemblage structures, calculated by Piankas index, was relatively high in a large-sized microatoll (0.503–0.831: 3.6m in diameter), in which microhabitat associations of fishes were clearly observed. The present study suggests that a microhabitat association is one of the important factors responsible for organization of reef fish assemblages in a microatoll.  相似文献   

12.
Patterns of hard coral and sea urchin assemblage structure (species richness, diversity, and abundance) were studied in Kenyan coral reef lagoons which experienced different types of human resource use. Two protected reefs (Malindi and Watamu Marine National Parks) were protected from fishing and coral collection, but exposed to heavy tourist use. One reef (Mombasa MNP) received protection from fishermen for one year and was exploited for fish and corals prior to protection and was defined as a transitional reef. Three reefs (Vipingo, Kanamai, and Diani) were unprotected and experienced heavy fishing and some coral collection. Protected and unprotected reefs were distinct in terms of their assemblage structure with the transitional reef grouping with unprotected reefs based on relative and absolute abundance of coral genera. Protected reefs had slightly higher (p<0.01) coral cover (23.6 ± 8.3 % ± S.D.) than unprotected reefs (16.7 ± 8.5), but the transitional reef had the highest coral cover (30.8 ± 6.4) which increased by 250% since measured in 1987: largely attributable to a large increase inPorites nigrescens cover. Protected reefs had higher coral species richness and diversity and a greater relative abundance ofAcropora, Montipora andGalaxea than unprotected reefs. The transitional reef had high species richness, but lower diversity due to the high dominance ofPorites. Sea urchins showed the opposite pattern with highest diversity in most unprotected reefs. Coral cover, species richness, and diversity were negatively associated with sea urchin abundance, but the relative abundance ofPorites increased with sea urchin abundance to the point wherePorites composed >90% of the coral cover at sites with the highest sea urchin abundance. Effects of coral overcollection was only likely for the genusAcropora (staghorn corals). A combination of direct and indirect effects of human resource use may reduce diversity, species richness, and abundance of corals while increasing the absolute abundance of sea urchins and the relative cover ofPorites.  相似文献   

13.
We present the first in situ observations of the pelagic larvae of coral-reef fishes feeding, schooling and being preyed upon. In addition, we report on their behavioural interactions with adult and juvenile fishes. Observations on over 500 larvae of over 50 species (mostly from four families) near the end of their pelagic interval were made in both open water (> 1 km offshore) and near-reef environments. Nearly 10% of larvae were seen to feed in open water, but < 1% fed near the reef. Presettlement schooling was observed in five species of four families. We observed no predation upon larvae in open water except near the bottom. Near the reef, 8.5% of larvae were eaten. The main predators near and on the reef were a species of wrasse and lizardfishes. Rates of predation seem to differ among genera of pomacentrids, perhaps related to differences in behaviour when settling. When confronted with adult fishes, which happened largely near the reef, larvae reacted with a limited range of behaviours, including sheltering near the observer, swimming to the surface, slowing or stopping, or swimming offshore. The frequency of these behaviours differed among larvae of three pomacentrid genera. Interactions with reef residents, particularly pomacentrids, were common, and usually involved aggression by the resident toward settling larvae. This may act to discourage settlement during the day when such residents are active. These data show that behaviour of late larvae of coral-reef fishes is complex and can greatly influence survival and recruitment. Further, behaviour differs among taxa, showing that not only are larvae not passive, but also that a generalised behaviour of larvae does not exist.  相似文献   

14.
Small ribosomal subunits from the prokaryoteEscherichia coli and the eukaryoteThermomyces lanuginosus were imaged electron spectroscopically, and single particle analysis used to yield three-dimensional reconstructions of the net phosphorus distribution representing the nucleic acid (RNA) backbone. This direct approach showed both ribosomal RNAs to have a three domain structure and other characteristic morphological features. The eukaryotic small ribosomal subunit had a prominent bill present in the head domain, while the prokaryotic subunit had a small vestigial bill. Both ribosomal subunits contaied a thick collar central domain which correlates to the site of the evolutionarily conserved ribosomal RNA core, and the location of the majority of ribosomal RNA bases that have been implicated in translation. The reconstruction of the prokaryotic subunit had a prominent protrusion extending from the collar, forming a channel approximately 1.5 nm wide and potentially representing a bridge to the large subunit in the intact monosome. The basal domain of the prokaryotic ribosomal subunit was protein free. In this region of the eukaryotic subunit, there were two basal lobes composed of ribosomal RNA, consistent with previous hypotheses that this is a site for the non-conserved core ribosomal RNA.  相似文献   

15.
ATPase activity in rat heart sarcoplasmic reticulum was stimulated in a concentration-dependent manner by both Ca2+ and Mg2+ in the complete absence of the other cation. Increasing concentrations of Mg2+ produced an apparent inhibition of the Ca2+-dependent ATP hydrolysis. CDTA (trans-1,2-diaminocyclohexane-N,N,N,N-tetraacetate) had no effect on these responses. The results indicate the presence of a low affinity non-specific divalent cation-stimulated ATPase in rat heart sarcoplasmic reticulum. However, sarcoplasmic reticulum vesicles transported Ca2+ with a high affinity (K0.5 Ca2+ = 0.41 M) suggesting the presence of a high affinity Ca2+-transporting ATPase. Calmodulin did not stimulate rat heart sarcoplasmic reticulum ATPase activity over a range of Ca2+ and Mg2+ concentrations and failed to stimulate membrane phosphorylation and Ca2+ transport into sarcoplasmic reticulum vesicles. Calmodulin antagonists trifluoperazine and compound 48180 did not affect the ATPase activity. Catalytic subunit of cAMP-dependent protein kinase was also ineffective in stimulating the ATPase activity. These results suggest the presence of an ATPase activity in rat heart sarcoplasmic reticulum with different properties from the high affinity Ca2+-pumping ATPase previously characterized in dog heart and other species.Abbreviations cAMP adenosine 3,5-monophosphate - CaM calmodulin - CDTA trans-1,2-diaminocyclohexane-N,N,N,N-tetraacetate - EDTA ethylene-diaminetetraacetate - EGTA ethylene glycol bis(-aminoethyl ether)-N,N,N,N-tetraacetate - PLB phospholamban - SR sarcoplasmic reticulum - TFP trifluoperazine  相似文献   

16.
Synopsis An alternative to the reef fish lottery model is proposed for explaining instances of coexistence of reef fishes without apparent spatial resource partitioning. This model is termed money-in-the-bank because of a financial analogy used to explain it. It stresses the importance of habitats that can support only one of two or more closely related species that coexist elsewhere. Populations living in such monospecific habitats could, according to the model, produce enough larvae to repopulate these habitats plus an excess that may settle in the multispecific habitats. Possible examples among cardinalfishes are given.This paper forms part of the proceedings of a mini-symposium convened at Cornell University, Ithaca, N.Y., 18–19 May 1976, entitled Patterns of Community Structure in Fishes (G. S. Helfman, ed.).  相似文献   

17.
Ackerman JL  Bellwood DR  Brown JH 《Oecologia》2004,139(4):568-571
A key relationship in ecology is that between density and body size, with the emphasis placed on energetic rules constraining the abundance of larger organisms below that of smaller organisms. Most studies have focused upon the density-body size relationship at the species level. However, energy is gathered at an individual level. We therefore examined this relationship in a coral reef fish assemblage, focusing on individuals. Using a comprehensive data set, with over 14,000 observations we found that the relationship between local density and adult body size differs from the linear relationship predicted by the energetic equivalence rule. However, excluding the smallest size classes, the relationship between body size and individual abundance for intermediate to larger fish did not depart from the predicted –0.75. Unlike plants and intermediate to large reef fishes, the smallest fishes appear to have constraints that may reflect different patterns of resource acquisition.  相似文献   

18.
Summary The powdery mildew disease resistance gene Ml(La) was found to belong to a locus on barely chromosome 2. We suggest that this locus be designated MlLa. Linkage analysis was carried out on 72 chromosome-doubled, spring-type progeny lines from a cross between the winter var Vogelsanger Gold and the spring var Alf. A map of chromosome 2 spanning 119cM and flanked by two peroxidase gene loci was constructed. In addition to the Laevigatum resistance locus the map includes nine RFLP markers, the two peroxidase gene loci and the six-row locus in barley.  相似文献   

19.
Reef coring and NOAA/AVHRR imagery were used to examine differences in reef colonisation and accumulation across a gradient of increasing tidal range and turbidity. AVHRR channel-1 reflectance, which was strongly correlated with suspended sediment concentration (SSC), demonstrated that SSC is due to tidal resuspension of sediments, and increases with increasing tidal range. Underwater surveys and reef coring revealed that reef development diminishes with increasing SSC toward Broad Sound. Few reefs near Broad Sound have formed reef flats; those that have are thinner and accumulated more slowly during the Holocene. The many submerged reefs in this area represent a mixture of reef turn-ons and turn-offs. Some are probably incipient reefs in the early stages of reef growth. Others appear to be coral communities growing as thin veneers on exposed rock surfaces, rather than coral reef communities with capacity for reef-building. Still others developed reef flats earlier in the Holocene, and have since turned-off.  相似文献   

20.
Movement of coral reef fishes across marine reserve boundaries subsequent to their initial settlement from the plankton will affect the ability of no-take reserves to conserve stocks and to benefit adjacent fisheries. However, the mobility of most exploited reef species is poorly known. We tagged 1443 individuals of 35 reef fish species captured in Antillean fish traps in the Barbados Marine Reserve and adjacent non-reserve over a two-month period. Trapping and visual surveys were used to monitor the movements of these fish during the trapping period and the subsequent two months. Estimates of distances moved were corrected for the spatial distribution of sampling effort and for the number of recaptures of individual fish. Recapture rates for individual species ranged from 0–100% (median=38%). Species mobility estimated by recapture and resighting were highly correlated. Most species were strongly site attached, with the majority of recaptures and resightings occurring at the site of tagging. However, only one of 59 tagged jacks (Caranx latus, C. ruber) was ever resighted, suggesting emigration from the study area. All species were occasionally recorded away from the sites where they had been tagged (20–500m), and several species, including surgeonfish, Acanthurus bahianus, A. coeruleus, filefish, Cantherhines pullus, butterflyfish, Chaetodon striatus, angelfish Holocanthus tricolor and parrotfish, Sparisoma viride, ranged widely within reefs. In contrast, few movements were observed between reefs separated by more than 20m of sand and rubble, and no emigration from the Reserve was recorded. Most reef fishes vulnerable to Antillean traps appear sufficiently site-attached to benefit from reserves. However, many species move over a wide enough area to take them out of small reserves on continuous reef. Use of natural home range boundaries could minimize exposure of fishes in reserves to mortality from adjacent fisheries.  相似文献   

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