Considerations on the diet composition and feeding rate of dermersal sharks in 15 European public aquaria

To get an overview of the feeding practices applied to dermersal sharks in captivity, a questionnaire was sent to 15 European public aquaria. The most common dermersal shark species kept in the participating aquaria are Carcharhinus plumbeus (n=9), Carcharias taurus (n=7), and C. melanopterus (n=6). Body weight (BW) was calculated using captive estimated body length (BL) and actual weight data obtained from commercial fisheries. The estimated BW for C. plumbeus in all participating aquaria is higher than the calculated BW. The feeding rate (FR) for adult C. plumbeus varied widely within participating aquaria (2.3–11.5% BW_cal/week or 32–112 kcal/kg BW_cal/week). The FR for adult C. plumbeus was lower (1.2–7.9% BW_est/week or 17–99 kcal/kg BW_est/week) using the estimated BW. Adult Carcharias taurus were fed at 1.3–5.0% BW_cal/week or 70–170 kcal/kg BW_cal/week. Negaprion brevirostris was fed at 5.0% BW_est/week or 57 kcal/BW_est/week. The relationship between FR and estimated BW is expressed as FR=54.5 e^?0.033BW. In this study, the feeding frequency for C. plumbeus varied between 1–7 times a week, with an average of 3.3 times a week. Diet in all aquaria consisted of both lean and fatty fish, and sometimes squid or crustaceans. Supplementation of vitamins is common practice in 80% of the surveyed aquaria, although a wide variety of quantity and quality was observed. Ten aquaria (66%) add iodine, as potassium iodide (0.4–12.5 mg KI/kg BW/week) or calcium‐iodate (322–1,500 mg/kg food/week), to their food. Zoo Biol 22:203–226, 2003. © 2003 Wiley‐Liss, Inc.     

Coastal sharks and rays in a marine protected area in southern Brazil

In southern Brazil, we investigated shark and ray capture records in an integral protection marine protection area (MPA) that allows fishing in that area. We found 10 shark and nine ray species, of which 88.5% and 66.2%, respectively, are endangered. Female adults and neonates of both sexes are abundant in the area, with records of stranding of large specimens, postcapture abortions and ovigerous capsules with fresh embryos on the beach. We suggest the application of continuous fisheries monitoring and an increase in guidelines on the capture of endangered species.     

Barriers to hybridisation and their conservation implications for a highly threatened Australian fish species

Hybridisation and introgression are natural phenomena that may lead to the transfer of adaptive alleles from one species to another and increased species diversity. At the same time, hybridisation and subsequent introgression threaten many species world‐wide through the loss of genetic and species diversity. In Australia, introgressive hybridisation between native and alien species has not typically been considered a significant threat to native biodiversity because of the taxonomic distance between native and alien biota. However, many native fish have been introduced outside their natural range. Recently, four taxa in the genus Melanotaenia have been nationally listed as threatened due to introgressive hybridisation with introduced Melanotaenia splendida. We examined pre‐ and post‐zygotic barriers to hybridisation between M. splendida and one of these threatened taxa—Running River rainbowfish (RRR)—to assess the potential for hybridisation to occur. We used dichotomous mate choice experiments to examine pre‐zygotic barriers and mating experiments to examine post‐zygotic barriers. Size was not a significant predictor of the proportion of time subjects spent with a potential mate, nor was there any significant difference in the amount of time subjects spent with potential mates of their own or the opposite species. Eggs from hybrid pairings with female RRR had a slightly higher hatching rate than those from hybrid pairings with female M. splendida, but neither were significantly different from intraspecies crosses. We could not identify any definite barriers to hybridisation, demonstrating that the introduction of “native” fish species outside their natural range poses a higher risk of hybridisation than previously thought. We call for better education around the consequences of moving “native” fish and the development of rapid response plans to deal with recently established alien populations of Australian fish species in order to prevent future extinctions due to introgressive hybridisation.     

Evolutionary transitions among egg-laying,live-bearing and maternal inputs in sharks and rays

Sharks and rays are thought to have a large number of independent origins of live-bearing. We examined evolutionary transitions to live-bearing and maternal input to embryos in this subclass by optimizing reproductive characters onto a composite phylogeny. Egg-laying (40 per cent of all species) is the likely ancestral reproductive mode for this clade, and there is evidence that live-bearing has evolved independently 9–10 times and maternal input 4–5 times. Most transitions (12–15) have been toward live-bearing with provisioning limited to yolk. These have occurred from egg-laying ancestors or live-bearing taxa that provide maternal input to embryos. Only 2–3 transitions have occurred in the other direction, i.e. away from yolk-only bearing. Egg-laying has evolved from live-bearing ancestors in skates, Rajidae (25 per cent of all species) and possibly in the zebra shark, Stegostoma fasciata. Thus, although there has been an overall trend toward the evolution of live-bearing in elesmobranchs, the evolution of additional maternal input has been extremely labile.     

The cellular DNA content of sharks,rays and some other fishes

• 1.1. The haploid amount of DNA was determined for 31 species of elasmobranchs and 8 other non-teleost fishes.
• 2.2. The elasmobranchs have a modal DNA amount of about 4 pg, compared to 1 pg for the teleosts.
• 3.3. The DNA content of the other non-teleosts ranges from 1.2 at the low end to 142 pg for lungfishes that have been assayed.
• 4.4. Several characteristics that are common to DNA distributions in many different groups of organisms, such as a skewed distribution and the positive correlation between specialization and a low amount of DNA, are apparent here. The lungfishes appear to be an exception to the latter characteristic.

     

The use and abuse of photographic identification in sharks and rays

The use of photography to discriminate between individuals in a population using natural markings or aberrations is increasingly being utilized to support field research on elasmobranchs. This non-intrusive method has facilitated investigation of a wide variety of subjects including population composition, abundance estimates, residency and movement, demography and social behaviours. Here the first detailed review of photo-identification as a research technique for sharks and rays is provided, and its assumptions, current applications and potential highlighted. The limitations and practical considerations of photographic studies are also investigated with recommendations on initial survey design and ongoing data collection using current technology. Future directions are also explored with an emphasis on a move towards standardized approaches and automated recognition programmes to facilitate global collaborative work.     

基于能值的陆域受威胁和濒危物种价值估算——以福建省厦门市为例

开展受威胁和濒危物种价值评估是生物多样性研究的关键问题之一。当前受威胁和濒危物种研究正处于濒危等级界定和保护优先性确定阶段,存在不同保护等级交叉管理、价值评估方法欠缺及重复性计算等多方面问题。利用IUCN濒危等级和中国特有种等级名录确定厦门市不同濒危等级物种数,在此基础上利用能值转换率和修正的中国能值/货币比率对厦门市陆域受威胁和濒危物种价值进行估算。结果显示,通过多途径整理纳入估算的厦门市陆域野生动植物物种数为1444种,其中受威胁和濒危物种数为318种;2015年厦门市物种能值价值约为3.53×10~(11)元,2010年约为3.08×10~(11)元,其中两期受威胁和濒危物种能值价值均占物种总价值的88.31%;中国特有种等级对价值贡献最大达73.25%,其次是IUCN濒危等级达23.24%。研究表明,能值评估法能够客观凸显受威胁和濒危物种价值,研究结果可为生物多样性及物种保育的管理决策提供技术支撑。     

Trypanosomes in a declining species of threatened Australian marsupial, the brush-tailed bettong Bettongia penicillata (Marsupialia: Potoroidae)

The brush-tailed bettong (Bettongia penicillata), or woylie, is a medium-sized macropod marsupial that has undergone a rapid and substantial decline throughout its home range in the Upper Warren region of Western Australia over a period of approximately 5 years. As part of an investigation into possible causes of the decline a morphologically distinct Trypanosoma sp. was discovered by light microscopy in the declining population but was absent in a stable population within the Karakamia Wildlife Sanctuary. Further investigations employing molecular methods targeting variations in the 18s rRNA gene determined that the trypanosome was novel and was also present within the Karakamia population albeit at a much lower overall prevalence and individual parasitaemia levels. Phylogenetic analysis suggests the novel Trypanosoma sp. to be closely related to other trypanosomes isolated from native Australian wildlife species. Although it appears unlikely that the parasite is solely responsible for the decline in woylie population size, it may (singularly or in conjunction with other infectious agents) predispose woylies to increased mortality.     

Incidental invertebrate-derived DNA detection of invasive and threatened species in temperate dry Southeast Australian forest

Well-informed biodiversity conservation practice can often be precluded by poor species detectability. For example, populations being missed during surveys can lead to them being omitted from species lists or area management plans. iDNA (invertebrate-derived DNA) is a recently developed set of techniques for improving the detectability of elusive vertebrates by exploiting their associated invertebrates. Parasitic and scavenging invertebrates can be readily collected, and their gut contents DNA barcoded to detect local vertebrate diversity. However, most iDNA surveys have targeted mammals and have been carried out in tropical areas and/or rainforests. We carried out iDNA surveys targeting frogs in temperate dry sclerophyll forests in south-eastern Australia. We set mosquito traps broadcasting recorded frog calls with the aim of collecting frog-biting flies, which are attracted to frog calls. We collected 156 fly specimens, although none were of frog-biting species, and no frogs were detected via iDNA, despite many being observed in the field. However, two mammal and one reptile species were detected via iDNA: the feral cat (Felis catus: Felidae), domestic dog or dingo (Canis lupus: Canidae) and the threatened Rosenberg's monitor (Varanus rosenbergi: Varanidae). Vertebrate-sampling flies are likely highly abundant in the area since they were collected apparently incidentally in traps lacking appropriate attractants; a promising result for further surveys is different attractants are employed. This study is one of the few in which an invasive species has been detected through iDNA, and highlights its potential for improved detectability of threatened species outside of the tropics and early detection of invasive species.     

Assessing ant seed predation in threatened plants: a case study

Erodium paularense is a threatened plant species that is subject to seed predation by the granivorous ant Messor capitatus. In this paper we assessed the intensity and pattern of ant seed predation and looked for possible adaptive strategies at the seed and plant levels to cope with this predation. Seed predation was estimated in 1997 and 1998 at the population level by comparing total seed production and ant consumption, assessed by counting seed hulls in refuse piles. According to this method, ant seed predation ranged between 18% and 28%. A more detailed and direct assessment conducted in 1997 raised this estimate to 43%. In this assessment spatial and temporal patterns of seed predation by ants were studied by mapping all nest entrances in the studied area and marking the mature fruits of 109 reproductive plants with a specific colour code throughout the seed dispersal period. Intact fruit coats were later recovered from the refuse piles, and their mother plants and time of dispersal were identified. Seeds dispersed at the end of the dispersal period had a greater probability of escaping from ant seed predation. Similarly, in plants with late dispersal a greater percentage of seeds escaped from ant predation. Optimum dispersal time coincided with the maximum activity of granivorous ants because, at this time, ants focused their harvest on other plant species of the community. It was also observed that within-individual seed dispersal asynchrony minimised seed predation. From a conservation perspective, results show that the granivorous ant–plant interaction cannot be assessed in isolation and that the intensity of its effects basically depends on the seed dispersal pattern of the other members of the plant community. Furthermore, this threat must be assessed by considering the overall situation of the target population. Thus, in E. paularense, the strong limitation of safe-sites for seedling establishment reduces the importance of seed predation.     

Assessing ant seed predation in threatened plants: a case study

Erodium paularense is a threatened plant species that is subject to seed predation by the granivorous ant Messor capitatus. In this paper we assessed the intensity and pattern of ant seed predation and looked for possible adaptive strategies at the seed and plant levels to cope with this predation. Seed predation was estimated in 1997 and 1998 at the population level by comparing total seed production and ant consumption, assessed by counting seed hulls in refuse piles. According to this method, ant seed predation ranged between 18% and 28%. A more detailed and direct assessment conducted in 1997 raised this estimate to 43%. In this assessment spatial and temporal patterns of seed predation by ants were studied by mapping all nest entrances in the studied area and marking the mature fruits of 109 reproductive plants with a specific colour code throughout the seed dispersal period. Intact fruit coats were later recovered from the refuse piles, and their mother plants and time of dispersal were identified. Seeds dispersed at the end of the dispersal period had a greater probability of escaping from ant seed predation. Similarly, in plants with late dispersal a greater percentage of seeds escaped from ant predation. Optimum dispersal time coincided with the maximum activity of granivorous ants because, at this time, ants focused their harvest on other plant species of the community. It was also observed that within-individual seed dispersal asynchrony minimised seed predation. From a conservation perspective, results show that the granivorous ant–plant interaction cannot be assessed in isolation and that the intensity of its effects basically depends on the seed dispersal pattern of the other members of the plant community. Furthermore, this threat must be assessed by considering the overall situation of the target population. Thus, in E. paularense, the strong limitation of safe-sites for seedling establishment reduces the importance of seed predation.     

Overfishing drives over one-third of all sharks and rays toward a global extinction crisis

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The importance of habitat and life history to extinction risk in sharks, skates, rays and chimaeras

We compared life-history traits and extinction risk of chondrichthyans (sharks, rays and chimaeras), a group of high conservation concern, from the three major marine habitats (continental shelves, open ocean and deep sea), controlling for phylogenetic correlation. Deep-water chondrichthyans had a higher age at maturity and longevity, and a lower growth completion rate than shallow-water species. The average fishing mortality needed to drive a deep-water chondrichthyan species to extinction (Fextinct) was 38-58% of that estimated for oceanic and continental shelf species, respectively. Mean values of Fextinct were 0.149, 0.250 and 0.368 for deep-water, oceanic and continental shelf species, respectively. Reproductive mode was an important determinant of extinction risk, while body size had a weak effect on extinction risk. As extinction risk was highly correlated with phylogeny, the loss of species will be accompanied by a loss of phylogenetic diversity. Conservation priority should not be restricted to large species, as is usually suggested, since many small species, like those inhabiting the deep ocean, are also highly vulnerable to extinction. Fishing mortality of deep-water chondrichthyans already exploited should be minimized, and new deep-water fisheries affecting chondrichthyans should be prevented.     

Ecology and survival of Nigritella nigra, a threatened orchid species in Scandinavia

Nigritella nigra ssp. nigra (Orchidaceae) is the only taxon of the genus in Scandinavia, where it occurs as an endemic with a disjunct distribution, mostly in upland areas of central Norway and Sweden. Nigritella nigra is a boreal-alpine, basiophilous species of open grasslands and dry fens. Both the number of localities and the number of individuals in a majority of the localities, including the study area at Sølendet, Røros, central Norway, have declined in recent decades. The most important threat is the change in agricultural practices followed by overgrowing of land earlier harvested for hay or intensively grazed. The total population of N. nigra at Sølendet is estimated to be about 3000 individuals, the largest known. Flowering individuals have been counted annually and all 225 individuals in nine permanent plots have been recorded for twenty years. The population has a large proportion of long-lived individuals with a half-life of up to 8 years in particular cohorts. Flowering behaviour varies greatly and flowering rarely occurs several years in succession. Together with the reduced size of individuals after flowering, this indicates a high cost of flowering. Correlation analyses indicate that high precipitation in autumn and winter negatively affects flowering (in July) on dry grasslands. On damp grasslands, warmth in autumn and in May of the flowering year correlates positively with flowering density. Many individuals are killed in years with heavy microtine rodent grazing. Experimental mowing as a management measure, and apparently also cattle grazing, have positive effects on the population. Some small, shallow valleys with a good supply of base-rich water on its flat, sandy floor is the main N. nigra biotopes at Sølendet.     

An analytical approach for estimating fossil record and diversification events in sharks, skates and rays

Background

Modern selachians and their supposed sister group (hybodont sharks) have a long and successful evolutionary history. Yet, although selachian remains are considered relatively common in the fossil record in comparison with other marine vertebrates, little is known about the quality of their fossil record. Similarly, only a few works based on specific time intervals have attempted to identify major events that marked the evolutionary history of this group.

Methodology/Principal Findings

Phylogenetic hypotheses concerning modern selachians’ interrelationships are numerous but differ significantly and no consensus has been found. The aim of the present study is to take advantage of the range of recent phylogenetic hypotheses in order to assess the fit of the selachian fossil record to phylogenies, according to two different branching methods. Compilation of these data allowed the inference of an estimated range of diversity through time and evolutionary events that marked this group over the past 300 Ma are identified. Results indicate that with the exception of high taxonomic ranks (orders), the selachian fossil record is by far imperfect, particularly for generic and post-Triassic data. Timing and amplitude of the various identified events that marked the selachian evolutionary history are discussed.

Conclusion/Significance

Some identified diversity events were mentioned in previous works using alternative methods (Early Jurassic, mid-Cretaceous, K/T boundary and late Paleogene diversity drops), thus reinforcing the efficiency of the methodology presented here in inferring evolutionary events. Other events (Permian/Triassic, Early and Late Cretaceous diversifications; Triassic/Jurassic extinction) are newly identified. Relationships between these events and paleoenvironmental characteristics and other groups’ evolutionary history are proposed.     

Vibrio species associated with mortality of sharks held in captivity

Two urease-positiveVibrio spp. were isolated from a brown shark (Carcharhinus plumbeus) that died in captivity at a national aquarium. Morphological, biochemical, and molecular genetic studies revealed one of the isolates to beV. damsela; the other isolate was unique and has been classified asV. carchariae sp. nov. BothV. damsela andV. carchariae were found to be virulent for spiny dogfish (Squalus acanthias), causing death in less than 18 hours after intraperitoneal injection of ca. 4×10⁶ cells.V. damsela was strongly cytotoxic for Y1 adrenal cell monolayers;V. carchariae exhibited weak cytotoxicity for Y1 cells.V. damsela contained cryptic plasmids and both isolates were urease positive.V. carchariae was able to utilize urea as sole source of carbon and nitrogen.     

Towards meaningful monitoring: A case study of a threatened rodent

Detecting trends in species’ distribution and abundance are essential for conserving threatened species, and depend upon effective monitoring programmes. Despite this, monitoring programmes are often designed without explicit consideration of their ability to deliver the information required by managers, such as their power to detect population changes. Here, we demonstrate the use of existing data to support the design of monitoring programmes aimed at detecting declines in species occupancy. We used single‐season occupancy models and baseline data to gain information on variables affecting the occupancy and detectability of the threatened brush‐tailed rabbit‐rat Conilurus penicillatus (Gould 1842) on the Tiwi Islands, Australia. This information was then used to estimate the survey effort required to achieve sufficient power to detect changes in occupancy of different magnitudes. We found that occupancy varied spatially, driven primarily by habitat (canopy height and cover, distance to water) and fire history across the landscape. Detectability varied strongly among seasons, and was three times higher in the late dry season (July–September), compared to the early dry season (April–June). Evaluation of three monitoring scenarios showed that conducting surveys at times when detectability is highest can lead to a substantial improvement in our ability to detect declines, thus reducing the survey effort and costs. Our study highlights the need for careful consideration of survey design related to the ecology of a species, as it can lead to substantial cost savings and improved insight into species population change via monitoring.