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1.
    
The age, growth and maturity of bonnetheads Sphyrna tiburo inhabiting the estuarine and coastal waters of the western North Atlantic Ocean (WNA) from Onslow Bay, North Carolina, south to West Palm Beach, Florida, were examined. Vertebrae were collected and aged from 329 females and 217 males ranging in size from 262 to 1043 mm and 245 to 825 mm fork length, LF, respectively. Sex‐specific von Bertalanffy growth curves were fitted to length‐at‐age data. Female von Bertalanffy parameters were L = 1036 mm LF, k = 0·18, t0 = ?1·64 and L0 = 272 mm LF. Males reached a smaller theoretical asymptotic length and had a higher growth coefficient (L = 782 mm LF, k = 0·29, t0 = ?1·43 and L0 = 266 mm LF). Maximum observed age was 17·9 years for females and 16·0 years for males. Annual deposition of growth increments was verified by marginal increment analysis and validated for age classes 2·5+ to 10·5+ years through recapture of 13 oxytetracycline‐injected specimens at liberty in the wild for 1–4 years. Length (LF50) and age (A50) at 50% maturity were 819 mm and 6·7 years for females, and 618 mm and 3·9 years for males. Both female and male S. tiburo in the WNA had a significantly higher maximum observed age, LF50, A50 and L, and a significantly lower k and estimated L0 than evident in the Gulf of Mexico (GOM). These significant differences in life‐history parameters, as well as evidence from tagging and genetic studies, suggest that S. tiburo in the WNA and GOM should be considered separate stocks.  相似文献   

2.
    
An investigation was undertaken to determine whether photoperiod or temperature have an effect on the timing of vertebral opaque–transluscent band‐pair deposition in captive young‐of‐the‐year (YOY) little skate Leucoraja erinacea. The experimental design consisted of a randomized complete block split plot design with two factors: temperature and light. Temperature was nested within light and therefore four variables were tested: 1) constant light, 2) constant temperature, 3) seasonal light and 4) seasonal temperature. For 18 months, L. erinacea experienced accelerated seasonal conditions of temperature and light to mimic 3 years of growth. This study provides primary and supporting evidence that seasonal photoperiod and temperature, respectively, have no effect on timing of vertebral band‐pair deposition in captive L. erinacea. Vertebral analysis of surviving L. erinacea (n = 6, time = 18 months) showed that all produced 1–1·5 band pairs, while centrum edge analysis (n = 56) showed timing of winter and summer band deposition were similar regardless of treatment. The winter band (translucent) appeared in February 2007 and January 2008 while the summer band (opaque) showed up in July for both 2007 and 2008 and mimicked patterns observed in the wild. While temperature and photoperiod appear to have no effect on timing of band‐pair deposition in YOY L. erinacea, other mechanisms which may influence band deposition should be investigated including the effect of food ration and the presence of a circa‐annual rhythm and hormone secretion.  相似文献   

3.
The time taken for oxytetracycline to be incorporated as an intense, discrete band was determined by examining vertebrae and dorsal fin spines of Heterodontus portusjacksoni that were injected with oxytetracycline 2–180 days post-treatment. Oxytetracycline was visible in dorsal fin spines 2 days after treatment and 3 days after treatment in sectioned vertebrae. A distinct mark could not be identified in unsectioned vertebrae.  相似文献   

4.
    
Egg capsules of the Port Jackson shark Heterodontus portusjacksoni were examined during underwater visual census surveys at two sites in New South Wales, Australia, during the 2002–2005 reproductive seasons (austral winter). Embryonic mortality was high (0·783–0·896 per annum) with the majority (99·2%) resulting from predation. The crested horn shark Heterodontus galeatus and common tent shell Astralium tentoriformis (Gastropoda, Turbinidae) were positively identified as egg predators. Gastropod predation was insignificant, accounting for only 2·0 and 2·1% of total mortality at Terrigal Haven and Dent Rock, respectively. Most capsules appeared to have been depredated by large predatory fishes with the eastern blue groper Achoerodus viridis (Labridae) and the black stingray Dasyatis thetidis (Dasyatidae) as possible candidate predators. The rate of embryonic mortality in H. portusjacksoni is higher than that reported for other oviparous elasmobranchs. This high level of mortality has significant consequences for the conservation and management of this species, especially when combined with an understanding of their low fecundity, late maturity and protracted reproductive life.  相似文献   

5.
    
Sharks exhibit varied demographic strategies depending on both the species and the population location, which make them more or less vulnerable to fishing. Accurate evaluation of local age and growth parameters is therefore fundamental for the sustainable management of their stocks. Although demographic parameters have been assessed for bull shark (Carcharhinus leucas) populations in several locations of the world, this information is missing so far around Reunion Island, in the south-west Indian Ocean. To fill this gap of knowledge, age and growth data were gathered from the vertebrae of 140 individuals of C. leucas (77 females and 63 males, mostly adults) fished around the island between 2012 and 2019. After verification of the annual deposition of growth band pairs on these structures using relative marginal increment analysis on 40 individuals, band pairs were counted along the vertebral centrum for each individual. Thanks to this approach, growth was shown to significantly differ between male and female C. leucas around Reunion Island, with respective von Bertalanffy growth model equations of Lt =  and Lt = . Indeed, the females of the species fished in this area were significantly (P < 0.001) larger than local males, with an estimated difference in size of ~16.1 cm at 20 years old. They also apparently reach older ages, with an estimated maximum age of 33.50 years, against 29.75 years only for the males. The estimated size at birth around the island is larger than elsewhere in the world, varying from 92.30 to 100.00 cm depending on the method used. These results confirm that the population of C. leucas around Reunion Island exhibits a K-selected strategy, which makes it highly vulnerable to fishing pressure.  相似文献   

6.
7.
  总被引:2,自引:0,他引:2  
Small body size has been associated with long life span in four stocks of mutant dwarf mice, and in two varieties of dietary restriction in rodents. In this study, small body size at ages 2-24 months was shown to be a significant predictor of life span in a genetically heterogeneous mouse population derived from four common inbred mouse strains. The association was strongest for weights measured early in adult life, and somewhat weaker, though still statistically significant, at later ages. The effect was seen both in males and females, and was replicated in an independent population of the same genetic background. Body size at ages 2-4 months was correlated with levels of serum leptin in both males and females, and with levels of IGF-I and thyroid hormone in females only. A genome scan showed the presence of polymorphic alleles on chromosomes 2, 6, 7 and 15 with significant effects on body weight at 2-4 months, at 10-12 months, or at both age ranges, showing that weight gain trajectory in this stock is under complex genetic control. Because it provides the earliest known predictor of life span, body weight may be usefully included in screens for induced mutations that alter aging. The evidence that weight in 2-month-old mice is a significant predictor of life span suggests that at least some of the lethal diseases of old age can be timed by factors that influence growth rate in juvenile rodents.  相似文献   

8.
Historically, gymnurid rays have not done well in a captive environment. This report describes success in maintaining two specimens of the spiny butterfly ray, Gymnura altavela, in captivity. An aggressive husbandry protocol of tube feeding and force feeding maintained energy levels until the rays began to feed on their own. The rays used their pectoral fins to strike at food items, a behavior they may use in the wild to stun and capture prey. The first estimates of growth in captivity for any species of butterfly ray are given. Growth rates for the male averaged 0.063 mm/day (s.d.=0.030) and 10.253 g/day (s.d.=9.689), whereas growth rates for the female butterfly ray averaged 0.303 mm/day (s.d.=0.215) and 22.777 g/day (s.d.=15.2). Estimates of gross conversion efficiency (Kl) were calculated using the caloric values and known food intake. The estimates of Kl averaged 5.4% (s.d.=3.857) and 16.1% (s.d.=7.511) for the male and female, respectively, with a combined average of 10.8% (s.d.=7.95). These are the first estimates of Kl reported for any species of batoid using direct methods (growth rate and food intake). © 1996 Wiley-Liss, Inc.  相似文献   

9.
    
Nick O  Megan E 《Zoo biology》2012,31(2):197-205
An artificial uterus (AU) was constructed from clear and opaque acrylic and life-support and monitoring systems were attached. The dwarf ornate wobbegong shark (Orectolobus ornatus) was used to test the AU because recent research has shown that during pregnancy the uterine fluid composition changes with mid- to late-term embryos immersed in seawater. An artificial uterine fluid comprising filtered, autoclaved seawater was placed in the AU. Eight, sexually mature female O. ornatus were captured from the wild and held in captivity. Subsequent ultrasound examinations confirmed pregnancy in three of these females. Six late-term embryos (three males and three females) were removed surgically from one euthanized female and placed in the AU. Their condition was monitored for 18 days before \"birth\" on September 26, 2008. The subsequent survival and growth of the AU pups was compared with naturally born wobbegong pups in captivity over a 140-day monitoring period. The development in the AU did not have detrimental effects as there was no postpartum mortality and there were marked increases in total length and weight that did not differ significantly between the two groups.  相似文献   

10.
1. Centenarian species, defined as those taxa with life spans that frequently exceed 100 years, have long been of interest to ecologists because they represent an extreme end point in a continuum of life history strategies. One frequently reported example of a freshwater centenarian is the obligate cave crayfish Orconectes australis, with a maximum longevity reported to exceed 176 years. As a consequence of its reported longevity, O. australis has been used as a textbook example of life history adaptation to the organic‐carbon limitation that characterises many cave‐stream food webs. 2. Despite being widely reported, uncertainties surround the original estimates of longevity for O. australis, which were based on a single study dating from the mid‐1970s. In the present study, we re‐evaluated the growth rate, time‐to‐maturity, female age‐at‐first‐reproduction and longevity of O. australis using a mark–recapture study of more than 5 years based upon more than 3800 free‐ranging individuals from three isolated cave streams in the south‐eastern United States. 3. The results of our study indicate that accurate estimates of the longevity of O. australis are ≤22 years, with only a small proportion of individuals (<5%) exceeding this age. Our estimates for female time‐to‐maturity (4–5 years) and age‐at‐first‐reproduction (5–6 years) are also substantially lower than earlier estimates. 4. These new data indicate that the age thresholds for life history events of O. australis are comparable to other estimates for a modest assemblage of cave and surface species of crayfish for which credible age estimate exists, suggesting that a cave environment per se is not required for the evolution of extreme longevity in crayfish.  相似文献   

11.
    
This study developed a portable, low-cost field respirometer for measuring oxygen consumption rates of large-bodied fishes. The respirometer performed well in laboratory tests and was used to measure the oxygen consumption rates ( O2) of bull sharks Carcharhinus leucas (mean: 249.21 ± 58.10 mg O2 kg−1 h−1 at 27.05°C). Interspecific comparisons and assessments of oxygen degradation curves indicated that the respirometer provided reliable measurements of O2. This system presents a field-based alternative to laboratory respirometers, opening opportunities for studies on species in remote localities, increasing the ability to validate physiological field studies.  相似文献   

12.
The movement rates of sharks are intrinsically linked to foraging ecology, predator–prey dynamics and wider ecosystem functioning in marine systems. During ram ventilation, however, shark movement rates are linked not only to ecological parameters, but also to physiology, as minimum speeds are required to provide sufficient water flow across the gills to maintain metabolism. We develop a geometric model predicting a positive scaling relationship between swim speeds in relation to body size and ultimately shark metabolism, taking into account estimates for the scaling of gill dimensions. Empirical data from 64 studies (26 species) were compiled to test our model while controlling for the influence of phylogenetic similarity between related species. Our model predictions were found to closely resemble the observed relationships from tracked sharks, providing a means to infer mobility in particularly intractable species.  相似文献   

13.
    
Copper and lead substitution reactions were found to be useful in demonstrating growth patterns in vertebrae from several elasmobranch species. In contrast, iron substitution was ineffective in detecting variations in vertebral mineralization. The present study provides two alternative methods for elasmobranch age determination that may prove useful when traditional methods are deemed ineffective. However, species-specific variations in the efficiency of these methods reemphasize the observation that different types of vertebrae often require different methods of staining.  相似文献   

14.
    
Serial ultrasound examination of four mature female sevengill sharks (Notorynchus cepedianus) was carried out over 18 months. Monitoring the reproductive cycle and development of follicles and fetuses in sharks in a noninvasive manner using this technique has not been reported previously. Sharks were caught out of the “Oceanarium” tank by divers using a specially made catch‐out bag, and brought to a holding area for examination. A behavior scoring system was used to monitor the impact of regular handling on the well‐being of the animals. Ultrasound showed the growth and regression of follicles in sevengill ovaries, and allowed an approximation of the reproductive stage of these sharks. Monitoring behavior at five time points during the procedure showed that regular handling of sharks for clinical studies could be done with minimal impact on animal welfare. The ability to follow reproductive events in elasmobranches using ultrasonography is an important step in the application of assisted reproductive technology in these species. Assisted reproductive technology, such as monitoring female reproductive cycles and artificial insemination, could potentially be used to maintain genetic diversity and compliment aquaria‐based breeding programs for endangered species such as the gray nurse shark (Carcharias taurus). Zoo Biol 26:383–395, 2007. © 2007 Wiley‐Liss, Inc.  相似文献   

15.
Synopsis We determined age and growth, size at maturity, and fecundity for cownose rays, Rhinoptera bonasus, collected from the northern Gulf of Mexico. Vertebral age estimates ranged from 0+ to 18+ years for females and 0+ to 16+ years for males. Annual deposition of growth increments was verified with marginal increment analysis. Likelihood ratio tests indicated that the growth of the cownose ray was best described by a combined sexes Gompertz model. Median size at 50% maturity was determined to be 642 mm DW for males and 653 mm DW for females, or 4–5 years of age. Median pup size-at-birth was estimated to be 350 mm DW, with a gestation period of 11–12 months. In all cases, gravid females contained only one pup. Statistically significant differences were detected between growth curves for the Gulf of Mexico and the western Atlantic Ocean. Cownose rays in the Gulf of Mexico had lower estimates of DW and K, and a higher theoretical longevity than their conspecifics in the western Atlantic Ocean. Cownose rays in the Gulf of Mexico also attain maturity at a smaller size and earlier age than their counterparts in the western Atlantic Ocean.  相似文献   

16.
Values of M and M/K extracted from simulated uni-modal length-frequency data representing 28 fish stocks were biased. The bias exceeded 20% when the life span of the stock was <5 or >15 years.  相似文献   

17.
    
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18.
    
Ucides cordatus (Linnaeus, 1763), found in mangroves along the Brazilian coast, is an artisanal fishery resource harvested as a source of income and for subsistence. A 12?month study of U. cordatus was conducted in a mangrove area of the southeastern Brazilian coast to estimate the growth, longevity, sex ratio and population density of the crabs. A total of 1024 crabs (505 males and 519 females) were sampled. Carapace width (CW) ranged from 49 to 90?mm (mean?±?SD: 71.2?mm?±?6.0) for males and from 52 to 83?mm (69.3?mm?±?4.9) for females. Males dominated the largest CW classes. The asymptotic size (CW) and the asymptotic weight (WW) were estimated as 93.4?mm and 305.5?g, respectively, for males and as 87.1?mm and 221.5?g, respectively, for females. The estimated maximum longevities were 17.6?years for males and 15.7?years for females. The males (k?=?0.17, Φ?=?1.171) and females (k?=?0.19, Φ?=?1.159) showed similar growth rates. The mean density was 0.41?±?0.19?burrows?m?2. Of this total mean density, 85.8% corresponded to the immediate harvesting potential and 14.2% to the future harvesting potential. Given that U. cordatus is a long-lived species that grows slowly, an appropriate strategy for the management is crucial to ensure the sustainable exploitation of this resource.  相似文献   

19.
  总被引:1,自引:0,他引:1  
The average dairy cow survives only three lactations, reducing the availability of replacement heifers. Prenatal losses occur due to early embryonic mortality (about 40%), later embryo loss (up to 20% in high-yielding herds) or abortion (about 5%). A recent survey of 19 UK herds showed that 7.9% of calves were born dead and 3.4% died within 1 month. During the rearing phase, 6.7% of animals were lost before reaching first service at 15 months due to disease or accident and another 2.3% failed to conceive. Many potential replacements therefore never enter the milking herd. This severely limits opportunities for on-farm selection of breeding cows in addition to presenting a welfare issue and causing economic loss. The most profitable animals once lactation is reached combine good milk production with a regular calving pattern. Some aspects of performance are related to age at first calving (AFC), which in turn is influenced by heifer growth rates. Poorly growing animals required more services to conceive, calved later and subsequently performed badly. Optimum fertility and maximum yield in the first lactation were associated with an AFC of 24 to 25 months. However, heifers calving at 22 to 23 months performed best in terms of total milk yield and survival over the first 5 years, partly because good heifer fertility was associated with better fertility later. We have investigated some possible juvenile predictors of future performance. Low-birth-weight calves were more likely to come from either primiparous mothers or older dams (3+ lactations) with higher peak milk yields, suggesting that the uterine environment may limit prenatal calf growth due to competition for nutrients with maternal growth or milk production. Linear trait classification scores for frame size show genetic correlations with longevity. The skeletal measures of height and crown rump length in 1-month-old calves was correlated to subsequent stature, and frame size was correlated to weight at 15 months. It may thus be possible to predict performance from simple size measurements as juveniles. Neither endogenous nor stimulated growth hormone (GH) release in 6-month-old calves were related to milk yield in the first three lactations, but size of a stimulated GH peak was positively related to milk energy values in the first lactation. Cows with delayed ovulation (>45 days) in the first lactation had a higher GH pulse amplitude and lower IGF-I as a juvenile. Cows that partition excess energy into milk in their first lactation may suffer reduced longevity.  相似文献   

20.
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