基于渔获统计的太平洋岛国渔业资源开发利用现状评价

全面评价渔业资源开发利用状况能够为资源的合理利用提供依据,营养指标作为以生态系统为基础的渔业管理方法与模式在近年来广泛运用于渔业管理中,用于评估捕捞活动的影响。根据联合国粮农组织FAO提供的1950—2010年太平洋岛国的渔获生产统计数据,结合Fishbase提供的相关鱼种营养级(Trophic level,TL)以及Sea Around Us Project数据库提供的无脊椎动物营养级,探讨了1950—2010年澳大利亚、新西兰、基里巴斯和斐济等四国的渔获物平均营养级(Mean trophic level,MTL)的变化情况,以此判定各国海洋渔业资源可持续利用情况。结果表明:澳大利亚资源状况较好,尽管其MTL在1950—1984年以0.09/10a的速度下降,但通过剔除TL低于3.25的物种,从而排除生物量受环境影响而波动较大的植食动物、腐生生物和食浮游生物动物对MTL造成的影响,观察TL大于3.25渔获物平均营养级(~(3.25)Mean trophic level,~(3.25)MTL)的变化情况,其~(3.25)MTL在1950—2010年呈波动上升趋势,说明MTL的下降是由低营养级鱼种产量的增加所引起的。新西兰海洋渔业资源遭到了一定程度的破坏,尽管其MTL自20世纪70年代中期开始大幅上升,并在1990—2010年处于高水平上稳定波动,未出现明显的下降趋势;但在不统计TL低于3.25的物种情况下,其~(3.25)MTL经过1977—1980年的加速上升以及1981—1998年的缓慢上升,在1999—2010年稳定下降并趋于平衡。从基里巴斯和斐济整个海域的营养指标变化情况来看,两国渔业资源状况较好,但将基里巴斯和斐济渔业分为外海渔业和沿岸渔业两类时,伴随产量的持续上升,两国的外海渔业MTL均未出现明显的降低,资源处于加速开发状态;而两国的沿岸渔业MTL在近年来均出现下降,资源被过度捕捞。为促使渔业的可持续发展,各国需加强对资源的动态监测与评估,以掌握捕捞活动下资源的变化情况。     

Trophic segregation of Falkland Islands seabirds: insights from stable isotope analysis

Seabird colonies provide rare opportunities to study trophic segregation in an entire bird community. We here present data on nitrogen and carbon isotope ratios of eight species of seabirds from New Island, Falkland Islands, and compare trophic levels (TL) and foraging distributions. We included adult feathers representing the interbreeding season, as well as chick feathers or down representing the breeding season. The stable isotope ratios indicated differences in feeding areas and TLs between species, consistent with the data of previous conventional diet analyses and observations at sea. We further reviewed conventional and stable isotope seabird community studies calculating the means and ranges of TLs observed across these studies. The mean TL (3.7) of the seabird community on New Island was at the lower end of the mean value range (3.5–4.5), but not significantly different, from the reviewed seabird communities. Seabirds on New Island had a range of 1.3 TLs, which is on the upper end of ranges within a community (0.4–1.5), indicating strong trophic structuring.     

Taxonomy of the proterosuchid archosauriforms (Diapsida: Archosauromorpha) from the earliest Triassic of South Africa,and implications for the early archosauriform radiation

Proterosuchidae is one of the first clades of Archosauriformes (archosaurs and closely related species) to appear in the fossil record, with the richest sample of the group coming from the Lystrosaurus Assemblage Zone (earliest Triassic) of South Africa. Four nominal proterosuchid species were described from South Africa during the twentieth century (Proterosuchus fergusi, Chasmatosaurus vanhoepeni, Chasmatosaurus alexanderi and Elaphrosuchus rubidgei), but interpretations of their taxonomy have been widely disparate. The most recent taxonomic revision concluded that P. fergusi is the only valid species and that the other nominal species are junior subjective synonyms of this taxon. This proposal was based on the interpretation that anatomical differences between the nominal species could be explained as a result of ontogenetic changes and/or post‐mortem deformation. The recent discoveries of multiple new South African proterosuchid specimens provide an impetus to revisit their taxonomy. Based upon a comprehensive re‐examination of all known specimens, as well as examination of other proterosuchid taxa in collections worldwide, we conclude that the holotype of Proterosuchus fergusi is undiagnostic. As a result, we propose a neotype (RC 846) for the species. ‘Chasmatosaurus vanhoepeni’ and ‘Elaphrosuchus rubidgei’ are considered subjective junior synonyms of P. fergusi. ‘Chasmatosaurus’ alexanderi is considered a valid species, for which we propose the new combination P. alexanderi comb. nov. A third species, P. goweri sp. nov., is erected on the basis of a single specimen (NMQR 880). All three species recognized here are taxonomically distinct from a previously described archosauriform maxilla from the lower Lystrosaurus AZ. As a result, we recognize a minimum of four archosauriform species following the Permo‐Triassic mass extinction in South Africa. Our results suggest a greater species richness of earliest Triassic archosauriforms than previously appreciated, but that archosauriform morphological disparity remained low and did not expand until the late Early Triassic – early Mid‐Triassic.     

Relationships between zooplankton abundance and trophic state in seven New Zealand lakes

The zooplankton communities of seven Rotorua, New Zealand, lakes of different trophic status were studied in 1977–78. They were generally dominated by the calanoid copepod, Calamoecia lucasi. Bosmina meridionalis occurred in all the lakes and Ceriodaphnia dubia in most. Only small numbers of Macrocyclops albidus ever occurred. Rotifers were not studied in detail. Community composition was similar to that in other northern New Zealand lakes. No well defined patterns of seasonal change in abundance were found and the timing of changes, which were of low magnitude, was different in each lake. Clutch sizes in all species were small. Calamoecia population parameters were analysed using multivariate methods and shown to be related to lake trophic level. Population densities were higher in more productive lakes whereas breeding levels were inversely related to indices of trophic status and population abundance. It is suggested that the populations, as in other northern New Zealand lakes, are food-limited, probably as a consequence of a lack of marked climatic seasonality and the absence of major predation pressures. Groupings of the lakes based on the Calamoecia data are in general agreement with those derived from parallel studies of water chemistry, phytoplankton and macrobenthos.     

Compensatory partitioning of carbon budgets by the grass shrimp (Palaemonetes pugio) and implications for predator prey relationships

Carbon utilization and allocation were examined between two populations of shrimp (Palaemonetes pugio) to determine the possible effects of living in an area of high anthropogenic impact. Carbon assimilation has been studied in P. pugio, but no study has looked at how assimilation might be influenced by contaminants. Anthropogenic effects on carbon assimilation in grass shrimp represent a major unmeasured impact on the carbon budget of multi-cellular organisms in estuaries and near shore environments. The influence of anthropogenic contamination on carbon assimilation has implications for predicting the environmental impact of contaminants, for models of estuarine function, and trophic transfer from the dominant macroscopic detritus processor to species of direct economic importance. Shrimp budgets were compared between two populations, one from a highly polluted marsh creek system in Northern New Jersey, and one from a clean reference site in Southern New Jersey. All components of the carbon budgets were measured directly including carbon allocated to reproduction. Carbon lost to respiration was lower in shrimp from the polluted system allowing them to have increased reproductive output. This is examined in the context of previous studies that show lowered predation by a piscine predator at the polluted site, resulting in a trophic cascade and changes in ecosystem function due to anthropogenic impacts.     

Characterisation (δ13C and δ15N isotopes) of the food webs in a New Zealand stream in the Waitakere Ranges,with emphasis on the trophic level of the endemic frog Leiopelma hochstetteri

Abstract

Leiopelma hochstetteri, the most widespread of New Zealand's native frogs, is recognised as threatened, and is fully protected by legislation. As a first step to characterise the diet and trophic level of L. hochstetteri within streams in the Waitakere Ranges, Auckland, stable carbon and nitrogen isotope analyses were undertaken on a variety of sympatric terrestrial and aquatic plant and animal species, including adult frogs. These results show that: (1) aquatic and terrestrial food webs are linked by terrestrial inputs into the stream; (2) invertebrate and vertebrate predators separate well into distinct trophic groups, and (3) L. hochstetteri occupies an intermediate trophic position among predators, with a diet, at least as an adult, comprising terrestrial invertebrates. Shortfin eels and banded kokopu are identified as potential predators of L. hochstetteri, but data for rats are inconclusive. These results have important implications for the conservation of New Zealand native frog species and riparian stream habitat.     

Trophic modelling of a New Zealand rocky reef ecosystem using simultaneous adjustment of diet, biomass and energetic parameters

We present a balanced model of organic carbon flows through a temperate coastal ecosystem in New Zealand. The Te Tapuwae o Rongokako Marine Reserve is a 2452 ha no-take area including both rocky reef platforms and soft sediment, and covering the intertidal and subtidal communities to depths of approximately 50 m. The model includes 22 trophic groups, including birds, predatory and grazing invertebrates, detritivores, five groups of fish, microphytes, macroalgae, zooplankton, phytoplankton, bacteria and detritus. Initial parameterisations of the model were developed from video, diver and quadrat surveys in the study area, augmented by parameters derived from simple population models and scientific literature. A novel two stage balancing methodology is presented which adjusts biomasses, diet fractions, and energetic parameters of all trophic groups simultaneously, taking into account estimated parameter uncertainties and the highly variable magnitudes of flows through different groups (6 orders of magnitude). Most adjustments to the initial parameters necessary to balance the trophic model were < 20%, but large adjustments were needed for poorly observed groups such as bacteria, sponge, and phytoplankton. The balanced model is recognised as being one solution amongst many. In the model, 94% of the primary production remained ungrazed and formed particulate and dissolved organic detritus. The balanced model indicated that the reserve is relatively impoverished in terms of grazers and predators relative to New Zealand rocky reefs to the north. The model suggests that lobsters, which have increased in numbers since the reserve was established, are responsible for substantial predation on invertebrate groups which make up their prey (grazing, predatory, phytal/infaunal invertebrates). The level of predation on invertebrates by lobster in the model depends significantly on the extent to which lobsters in TTMR are consuming macroalgae.     

Seedling mortality and damage due to non‐trophic animal interactions in a northern New Zealand forest

Abstract The importance of non‐trophic animal damage (biting and uprooting without consumption) and mortality of canopy tree seedlings were investigated in a warm temperate forest, in northern New Zealand. Two hundred seedlings 10‐30 cm in height were monitored at 4‐6‐week intervals for 2 years. Non‐trophic animal damage accounted for more seedling mortality in the first year (37.5% of all mortalities) than any other cause. Of the seedlings damaged in non‐trophic animal interactions 73% were bitten off close to the ground and left uneaten and the remainder were uprooted. In the second year all non‐trophic animal damage and mortality ceased following the control of rabbits (Oryctolagus cuniculus), suggesting that rabbits were the major cause of this damage. Total annual mortality rates (6‐8%) were low. However, measured seedling growth rates indicated an average time for seedlings to grow from 10 to 30 cm of 37 years. Therefore, in the absence of rabbit control, mortality due to non‐trophic animal interactions (3% per year) can have an important cumulative effect. Non‐trophic animal damage found in the present study before rabbits were culled (5% per year) was similar to that reported for two tropical forests, but much less than that reported for some other tropical and temperate forests.     

Regularities in Primary Production,Secchi Depth and Fish Yield and a New System to Define Trophic and Humic State Indices for Lake Ecosystems

General relationships between phytoplankton production, chlorophyll, total, dissolved and particulate phosphorus, Secchi depth, humic level, trophic level, fish production and latitude are described by regression equations using an extensive “Soviet” data base covering a wide domain of lake characteristics and a European data base. New systems for defining lake trophic and humic status are presented. The results may be used for more precise estimates of fundamental lake properties and for many practical issues of lake management, e.g., predictions of fish catch. We have used strict chlorophyll‐a concentrations for every trophic class and we have omitted Secchi depth from the trophic classes, since Secchi depth and other variables strongly related to water clarity (like suspended particulate matter and particulate organic carbon) depend on autochthonous production, allochthonous influences and resuspension. We have used the Secchi depth as a simple operational measure of the effective depth of the photic zone. It has also been shown that among these lakes there exist a very strong relationship between primary production and latitude. In fact, 74% of the variability among the lakes in mean summer primary production can be statistically related to variations in latitude. These data also show a strong relationship between primary production and fish yield, which can be used to address many fundamental issues in lake management, like “normal and abnormal fish production”.     

Distribution of rotifers in North Island,New Zealand,and their potential use as bioindicators of lake trophic state

The distribution and ecology of planktonic rotifers was investigated in 33 lakes in the North Island, New Zealand, between 1997 and 1999. A total of 79 species of monogonont rotifer were identified, with an average of 21 species per lake, a diversity which is high in comparison with many previous New Zealand studies. Most species recorded were cosmopolitan taxa, and were widespread in their distribution over the North Island. Multivariate analyses (Multi-Dimensional Scaling and Canonical Correspondence Analysis) did not distinguish distinct lake groupings based on rotifer communities, but rather gradients in assemblages, which were most highly associated with lake trophic state. Based on these responses, the development of potential rotifer bioindicator schemes for lake trophic state is described and discussed.     

Untangling interactions: do temperature and habitat fragmentation gradients simultaneously impact biotic relationships?

Gaining insight into the impact of anthropogenic change on ecosystems requires investigation into interdependencies between multiple drivers of ecological change and multiple biotic responses. Global environmental change drivers can act simultaneously to impact the abundance and diversity of biota, but few studies have also measured the impact across trophic levels. We firstly investigated whether climate (using temperature differences across a latitudinal gradient as a surrogate) interacts with habitat fragmentation (measured according to fragment area and distance to habitat edges) to impact a New Zealand tri-trophic food chain (plant, herbivore and natural enemy). Secondly, we examined how these interactions might differentially impact both the density and biotic processes of species at each of the three trophic levels. We found evidence to suggest that these drivers act non-additively across trophic levels. The nature of these interactions however varied: location synergistically interacted with fragmentation measures to exacerbate the detrimental effects on consumer density; and antagonistically interacted to ameliorate the impact on plant density and on the interactions between trophic levels (herbivory and parasitoid attack rate). Our findings indicate that the ecological consequences of multiple global change drivers are strongly interactive and vary according to the trophic level studied and whether density or ecological processes are investigated.     

Colonization of a novel depauperate habitat leads to trophic niche shifts in three desert lizard species

In a novel, depauperate ecosystem, colonizing species may experience changes in their trophic niche as a result of a new resource base and fewer competitors and predators. To examine trophic niche shifts of recent colonists, we focused on three ecologically and phylogenetically divergent lizard species that inhabit both the geologically distinctive depauperate habitat of White Sands and the surrounding Chihuahuan ‘dark soil’ desert in New Mexico. In White Sands the three species comprise the entire lizard community, whereas in the dark soils habitat, they constitute less than half of the lizard community abundance. As a result, we hypothesized that the three focal species would collectively represent a greater variety of trophic positions in the White Sands habitat than in the dark soils habitat. We hypothesized that the extent of shifts in each species’ trophic position would parallel diet and ecomorphology differences between habitats. To test these hypotheses, we combined analysis of lizard stomach contents with carbon and nitrogen stable isotopes in the context of previously published ecomorphology measurements. Stable isotope data indicated that as predicted, species were more different from one another in White Sands than in dark soils, suggesting community‐wide ecological release. Overall, all species were lower on the White Sands food chain; however, only one species decreased trophic level significantly, one increased trophic level variance, and one did not change significantly. Furthermore, stomach content data paralleled both stable isotope and ecomorphological data, showing different degrees of dietary overlap between habitats, depending on the species. That species’ differences in trophic ecology also correspond with ecomorphological differences suggests that these factors are either causally linked or collectively responding to similar ecological pressures, such as competition. By examining diet, trophic position, and ecomorphology of three colonist species, we demonstrate both species‐specific and community‐wide trophic differences in adjacent, but distinct habitats.     

Trophic cascades revealed in diverse ecosystems

New studies are documenting trophic cascades in theoretically unlikely systems such as tropical forests and the open ocean. Together with increasing evidence of cascades, there is a deepening understanding of the conditions that promote and inhibit the transmission of predatory effects. These conditions include the relative productivity of ecosystems, presence of refuges and the potential for compensation. However, trophic cascades are also altered by humans. Analyses of the extirpation of large animals reveal loss of cascades, and the potential of conservation to restore not only predator populations but also the ecosystem-level effects that ramify from their presence.     

Variation in δ<Superscript>13</Superscript>C and δ<Superscript>15</Superscript>N trophic enrichment factors among <Emphasis Type="Italic">Hyalella azteca</Emphasis> amphipods from different lakes

Stable isotopes are a powerful tool used to study the diets of animals because they provide information on food assimilated over an extended period. However, trophic enrichment factors used to reconstruct diets sometimes vary substantially, even among animals from the same trophic level. The goal of this study was to verify if trophic enrichment factors vary among animals as similar as Hyalella azteca amphipods from different lakes. We compared the carbon and nitrogen isotopic compositions of amphipods from different lakes fed on leaf detritus and on periphyton. Amphipods showed significant differences in their trophic enrichment factors among treatments (about 3.0‰ for carbon and nitrogen). The trophic enrichment factor of carbon was more affected by the food type, whereas the trophic enrichment factor of nitrogen was more affected by lake of origin. We estimated that amphipods had a tissue turnover of 25 days for carbon and 34 days for nitrogen. Our study showed that animals from different lakes can exhibit substantial variation in their trophic enrichment factors. This strengthens the view that trophic enrichment factors specific to a study system should be used whenever possible to reconstruct the in situ diet of consumers.     

The roles of predation,competition, and exploitation in the trophic dynamics of a warmwater stream: a model synthesis,analysis, and application

We developed a trophic dynamic model of key populations and processes in the New River, West Virginia, to identify the mechanisms most responsible for maintaining food web structure. Key populations were represented by thirteen model components and were aquatic insects; age-1 and age-2 crayfish (three species); age-1 and age-2 hellgrammites (Corydalus cornutus larvae); non-game fishes; age-0, age-1, and adult smallmouth bass (Micropterus dolomieu); age-0, age-1, and adult rock bass (Ambloplites rupestris); and age-0, age-1 to age-3, and adult flathead catfish (Pylodictis olivaris). In this system, crayfish and hellgrammites are harvested to provide bait for the recreational fishery that extensively exploits the three predatory fish species. Predation and intraspecific regulation were represented with nonlinear algorithms, and linear terms represented fishery harvests. Interspecific competition among components occurred through predation on shared prey. Error analysis of the model suggested that predation was the most important mechanism in maintaining system structure (the disposition of biomass among system components). Further, the trophic relation between each component and its prey accounted for 34–64% of the variability in food web structure, whereas predation on each component explained 1–24% of food web structure variability. Therefore, so-called ‘bottom-up’ effects were more influential than ‘top-down’ effects. Interspecific competition and intraspecific regulation had secondary roles in maintaining New River food web structure, although intraspecific regulation was most important to aquatic insects, which were not predatory in our model. Both forms of competition are probably tempered by extensive predation and exploitation in the New River system. Exploitation was a secondary structuring agent to adult smallmouth bass, which experience a high rate of harvest in the New River.     

The diet and trophic niche of orange perch, Lepidoperca aurantia (Serranidae: Anthiinae) on Chatham Rise, New Zealand

The diet of the New Zealand orange perch, Lepidoperca aurantia, was determined from examination of stomach contents of 248 specimens, primarily adults, sampled by bottom trawl on Chatham Rise, east of South Island, New Zealand, over three years. The diet was dominated by euphausiids (87% of total prey weight), with the remainder comprising mostly hyperiid amphipods (4%) and semi-pelagic teleost fish (7%). Orange perch are selective feeders specialising on small semi-pelagic crustaceans. They have an estimated trophic level of 3.4, classifying them as low-level carnivores. A multivariate analysis examined the influence on diet of a set of biological and environmental predictors; year and time of day were found to be the most influential variables, explaining 24% of the deviance in diet.     

Some Coelozoic Myxosporida From New Zealand Fishes: Family Sphaerosporidae1

SYNOPSIS. The trophic stages and spores of Sphaerospora undulans n. sp. from the urinary bladder, and ureters, and oviducts of Caulopsetta scapha, and the urinary bladder and ureters of Peltorhamphus novaezelandiae are described. An undescribed species from Genypterus blacodes is also mentioned. The host fishes were taken in New Zealand.     

Is Bocourt’s Terrific Skink Really So Terrific? Trophic Myth and Reality

Many scientists argue that our planet is undergoing a mass extinction event that is largely due to human influences. In this context, rediscoveries of species presumed to be extinct are encouraging and of great potential interest. During a 2003 expedition to New Caledonia, Bocourt’s terrific skink, Phoboscincus bocourti, was unexpectedly rediscovered on a small islet by one of us. This skink species had been described from a single specimen collected around 1872 in New Caledonia. Since that time, however, no data on the species’ biology, trophic interactions, or role in the ecosystem have been collected, making it difficult to follow the established conservation plan. In this study, we used a multidisciplinary approach involving natural history, anatomy, morphology, genetics, and stable isotopes to elucidate the ecology of Bocourt’s terrific skink. Over the course of three different expeditions to the islet (total of 55 days across 2005 and 2012), we captured 4 individuals and observed another 4 individuals. The species’ dentition and trophic ecology suggest that it is a top predator in its ecosystem and a major consumer of small terrestrial reptiles. Its high degree of genetic relatedness to another New Caledonian skink, which has a broad distribution, suggests that P. bocourti underwent genetic isolation at a geographical remote location, where dispersal or colonization was highly improbable. Moreover, the lack of genetic variation among the four individuals we captured may imply that a unique lineage, characterized by few inter-island exchanges, exists on the islet. Bocourt’s terrific skink may be the largest terrestrial squamate predator alive in New Caledonia today. As a result, it is likely vulnerable to habitat modifications and especially the invasive rodents found on this islet. Further information is necessary to assess the conservation plans and practices in place as no concrete changes have been made since the species’ rediscovery almost 10 years ago.