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1.
Reproductive aspects of the Atlantic angel shark Squatina dumeril in the southern Caribbean Sea
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The maturity and reproduction of the Atlantic angel shark Squatina dumeril were assessed using 77 females (29·2–110·4 cm total length; LT) and 269 males (58·7–108·2 cm LT) harvested by artisanal gillnetters off Venezuela. The biased sex ratio implied segregation or sex‐specific gear selectivity. Based on the development of the reproductive tract, 50% LT at sexual maturity (LT50, mean ± s.e .) for females and males were estimated at 86·14 ± 0·64 and 81·55 ± 0·12 cm, respectively. Uterine fecundity ranged between one and six and with a maximum embryo size of 25·7 cm LT. Gravid females were observed from August to December, including those close to parturition and while the gestation period was not confirmed, the size of ovarian follicles among some specimens implied protraction. The low fecundity of the species supports close monitoring of catches. 相似文献
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R. R. Licandeo† J. G. Lamilla P. G. Rubilar‡ R. M. Vega§ 《Journal of fish biology》2006,68(2):488-506
The age and growth parameters of Dipturus chilensis were estimated by counting growth rings from thin sections of vertebral centra from 400 fish (246 females and 154 males), ranging from 23 to 124 cm total length (LT), and backcalculating fish lengths at previous ages. Marginal increment analysis lent support to the hypothesis of annual deposition of band‐pairs, which formed during the winter months. The oldest female D. chilensis aged in this study was 21 years and 117 cm LT, whereas the oldest male was 18 years and 93 cm LT. A 4·7% index of average per cent error (IAPE) suggested that this is a precise method for calculating the age of D. chilensis. Observed LT were lower than backcalculated LT, which implies the influence of Lee's phenomenon. The von Bertalanffy growth equations, based on mean length‐at‐age data, were estimated as Lt = 128·3 (1 ? e?0·112 (t + 0·514)) for females and Lt = 107·8 (1 ? e?0·134 (t + 0·862)) for males where t is age (years). Growth was significantly different between sexes: females reached a larger adult size. Ages and lengths at 50% maturity were estimated at 14 years of age and 106 cm LT for females and 11 years of age and 86 cm LT for males. At c. 14 years, there was a decline in growth rates in females. The factor most likely responsible for this was sexual maturity, which caused a discontinuity in growth of female fish. These results show that this species is slow‐growing, long‐lived, relatively large and of delayed maturity, characteristics that make it vulnerable to exploitation. 相似文献
4.
Life‐history strategies of the rock hind grouper Epinephelus adscensionis at Ascension Island
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E. T. Nolan K. J. Downes A. Richardson A. Arkhipkin P. Brickle J. Brown R. J. Mrowicki Z. Shcherbich N. Weber S. B. Weber 《Journal of fish biology》2017,91(6):1549-1568
Epinephelus adscensionis sampled from Ascension Island, South Atlantic Ocean, exhibits distinct life‐history traits, including larger maximum size and size at sexual maturity than previous studies have demonstrated for this species in other locations. Otolith analysis yielded a maximum estimated age of 25 years, with calculated von Bertalanffy growth parameters of: L∞ = 55·14, K = 0·19, t0 = ?0·88. Monthly gonad staging and analysis of gonad‐somatic index (IG) provide evidence for spawning from July to November with an IG peak in August (austral winter), during which time somatic growth is also suppressed. Observed patterns of sexual development were supportive of protogyny, although further work is needed to confirm this. Mean size at sexual maturity for females was 28·9 cm total length (LT; 95% C.I. 27·1–30·7 cm) and no females were found >12 years and 48·0 cm LT, whereas all confirmed males sampled were mature, >35·1 cm LT with an age range from 3 to 18 years. The modelled size at which 50% of individuals were male was 41·8 cm (95% C.I. 40·4–43·2 cm). As far as is known, this study represents the first comprehensive investigation into the growth and reproduction of E. adscensionis at its type locality of Ascension Island and suggests that the population may be affected less by fisheries than elsewhere in its range. Nevertheless, improved regulation of the recreational fishery and sustained monitoring of abundance, length frequencies and life‐history parameters are needed to inform long‐term management measures, which could include the creation of marine reserves, size or temporal catch limits and stricter export controls. 相似文献
5.
Slow growth of the overexploited milk shark Rhizoprionodon acutus affects its sustainability in West Africa
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Age and growth of Rhizoprionodon acutus were estimated from vertebrae age bands. From December 2009 to November 2010, 423 R. acutus between 37 and 112 cm total length (LT) were sampled along the Senegalese coast. Marginal increment ratio was used to check annual band deposition. Three growth models were adjusted to the length at age and compared using Akaike's information criterion. The Gompertz growth model with estimated size at birth appeared to be the best and resulted in growth parameters of L∞ = 139·55 (LT) and K = 0·17 year?1 for females and L∞ = 126·52 (LT) and K = 0·18 year?1 for males. The largest female and male examined were 8 and 9 years old, but the majority was between 1 and 3 years old. Ages at maturity estimated were 5·8 and 4·8 years for females and males, respectively. These results suggest that R. acutus is a slow‐growing species, which render the species particularly vulnerable to heavy fishery exploitation. The growth parameters estimated in this study are crucial for stock assessments and for demographic analyses to evaluate the sustainability of commercial harvests. 相似文献
6.
Some observations on the biology of two rarely seen deep‐sea chimaerids,Chimaera carophila and Hydrolagus homonycteris
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Chimaera carophila (n = 45) and Hydrolagus homonycteris (n = 11), two deep‐sea chimaerids rarely caught in the waters off New Zealand, were collected from research trawl catches and commercial fishery catches around New Zealand at depths between 400 and 1300 m, between 2014 and 2016. Additional preserved specimens of both species (n = 58) from museum collections were analysed for size, sex and maturity. External assessment of male claspers and a combination of internal assessments of female gonad mass and oviducal gland width, were used to determine maturity. For both species, length at first maturity was 0·70–0·82 of their maximum observed chimaera length (LC), with females maturing at a larger size. Length at maturity for C. carophila (LC range: 28·7–103·9 cm) was estimated at 72·5 cm LC for males (n = 163) and 82·5 LC for females (n = 58). In H. homonycteris, length at maturity (length range: 78·6–99·8 cm LC) was estimated at 79·1 cm LC for males (n = 51) and 80·1 cm LC for females (n = 17). Ovarian fecundity was up to 31 for C. carophila and sperm storage was confirmed in the oviducal gland of this species. Both species preyed on benthic invertebrates. Some C. carophila and H. homonycteris inhabit depths beyond most current fisheries, but both species appear to be relatively rare and have reproductive parameters characteristic of low productivity, which may make these species vulnerable to population decline if mortality was to increase in the future. 相似文献
7.
Age,growth and maturity of the pelagic thresher Alopias pelagicus and the scalloped hammerhead Sphyrna lewini
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Indonesia has the greatest reported chondrichthyan catches worldwide, with c.110,000 t caught annually. The pelagic thresher (Alopias pelagicus) and scalloped hammerhead (Sphryna lewini) together comprise about 25% of the total catches of sharks landed in Indonesia. Age and growth parameters were estimated for A. pelagicus and S. lewini from growth‐band counts of thin‐cut vertebral sections. Alopias pelagicus (n = 158) and S. lewini (n = 157) vertebrae were collected from three Indonesian fish markets over a 5 year period. A multi‐model analysis was used to estimate growth parameters for both species. The models of best fit for males and females for A. pelagicus was the three‐parameter logistic (L∞ = 3169 mm LT, k = 0·2) and the two‐parameter von Bertalanffy models (L∞ = 3281 mm LT, k = 0·12). Age at maturity was calculated to be 10·4 and 13·2 years for males and females, respectively, and these are the oldest estimated for this species. The samples of S. lewini were heavily biased towards females, and the model of best fit for males and females was the three‐parameter Gompertz (L∞ = 2598 mm LT, k = 0·15) and the two‐parameter Gompertz (L∞ = 2896 mm LT, k= 0·16). Age at maturity was calculated to be 8·9 and 13·2 years for males and females, respectively. Although numerous age and growth studies have previously been undertaken on S. lewini, few studies have been able to obtain adequate samples from all components of the population because adult females, adult males and juveniles often reside in different areas. For the first time, sex bias in this study was towards sexually mature females, which are commonly lacking in previous biological studies on S. lewini. Additionally, some of the oldest aged specimens and highest age at maturity for both species were observed in this study. Both species exhibit slow rates of growth and late age at maturity, highlighting the need for a re‐assessment of the relative resilience of these two globally threatened sharks at current high levels of fishing mortality throughout the eastern Indian Ocean. 相似文献
8.
The reproductive biology and diet of prickly dogfish Oxynotus bruniensis, a deep‐sea elasmobranch, endemic to the outer continental and insular shelves of southern Australia and New Zealand, and caught as by‐catch in demersal fisheries, are described from specimens caught in New Zealand waters. A total of 53 specimens were obtained from research surveys and commercial fisheries, including juveniles and adults ranging in size from 33·5 to 75·6 cm total length (LT). Estimated size‐at‐maturity was 54·7 cm LT in males and 64·0 cm LT in females. Three gravid females (65·0, 67·5 and 71·2 cm LT) were observed, all with eight embryos. Size‐at‐birth was estimated to be 25–27 cm LT. Vitellogenesis was not concurrent with embryo development. Analysis of diet from stomach contents, including DNA identification of prey using the mitochondrial genes cox1 and nadh2, revealed that O. bruniensis preys exclusively on the egg capsules of holocephalans, potentially making it the only known elasmobranch with a diet reliant solely upon other chondrichthyans. Based on spatial overlap with deep‐sea fisheries, a highly specialized diet, and reproductive characteristics representative of a low productivity fish, the commercial fisheries by‐catch of O. bruniensis may put this species at relatively high risk of overfishing. 相似文献
9.
Reproductive biology of albacore Thunnus alalunga 总被引:1,自引:0,他引:1
Reproductive variables in albacore Thunnus alalunga were evaluated by gonad histology in samples of 132 males (58–118 cm fork length, LF) and 112 females (59–101 cm LF) that were collected from the western North Pacific Ocean from 2001 to 2006. In the sex ratio examination, males greatly outnumbered females in large adult fish (LF > 100 cm). Thunnus alalunga exhibited a protracted spawning period from March to September in the waters off eastern Taiwan and the Philippines, and the peak spawning activity occurred in March and April. Minimum sizes associated with the classification of mature fish were 78 and 83 cm LF for males and females, respectively. In addition, the largest LF of immature fish were 93 cm for males and 94 cm for females. The spawning frequency estimate in April was 1·7 days. Batch‐fecundity estimates of 21 females (89–99 cm LF) ranged between 0·17 and 1·66 million eggs (mean ±s.d . = 0·94 ± 0·43). The relative fecundity estimates of the 21 females ranged between 9·2 and 92·4 oocytes g?1 body mass (mean ±s.d . = 50·5 ± 22·8). The results presented in this study provide increased information regarding this species' reproductive‐related characteristics than are currently available in stock status determinations. 相似文献
10.
Population biology of an endangered species: the common guitarfish Rhinobatos rhinobatos in Lebanese marine waters of the eastern Mediterranean Sea
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M. Lteif R. Mouawad G. Khalaf P. Lenfant M. Verdoit‐Jarraya 《Journal of fish biology》2016,88(4):1441-1459
This study focuses on the population biology of the common guitarfish Rhinobatos rhinobatos, a cartilaginous fish listed as Endangered in the International Union for the Conservation of Nature (IUCN) Red List. Between December 2012 and January 2014, 67 individuals were collected by bottom longlining in coastal Lebanese marine waters at different ports at depths ranging from 10 to 110 m. The total length (LT) of the specimens ranged from 50 to 143 cm, and the mean ± s.d . was 76·2 ± 19·7 cm. The most common LT classes were between 60 and 70 cm. The total mass of the specimens ranged from 410 to 10 000 g, and the mean ± s.d . was 1841 ± 1987 g. A total of 34 males and 33 females were collected, and the sex ratio was not significantly different from 1:1. The mass and LT relationship showed positive allometric growth (b = 3·096 and r2 = 0·99), and the mean ± s.d . LT at which 50% of the individuals were sexually mature was 84·73 ± 5·81 cm for females and 78·57 ± 4·88 cm for males. The gonado‐somatic and hepato‐somatic indices were determined along with a condition factor, and parturition appeared to occur in winter. The primary prey items found in the fish stomachs during the autumn and winter seasons were Penaeidae. The results of this study will help to parameterize models of the population dynamics for this exploited fish stock to ensure the long‐term sustainability of its fishery. 相似文献
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12.
A. García Vásquez J.‐C. Alonso F. Carvajal J. Moreau J. Nuñez J.‐F. Renno S. Tello V. Montreuil F. Duponchelle 《Journal of fish biology》2009,75(10):2527-2551
The main life‐history traits of the dorado Brachyplatystoma rousseauxii, a large Amazonian catfish undertaking the largest migration known for a freshwater fish species (from the nursery area in the estuary of the Amazon to the breeding zones in the head waters of the western Amazon basin close to the Andes), were determined from a 5 year sampling of >15 000 specimens in the Peruvian Amazon. The breeding season occurred during the falling and low‐water periods, which is hypothesized to be an adaptation to maximize the chances of young stages to reach the estuary. The size at first sexual maturity was slightly larger for females than males, c. 91 and 83 cm standard length (LS), respectively. Both males and females reproduce for the first time at >3 years old. The fecundity per spawning event ranged from 481 734 to 1 045 284 oocytes for females weighing 25 and 34 kg, respectively. Seasonal variations of body condition were similar among sexes, but differed between immature specimens that had a higher condition during the low‐water period and lower condition during rising waters, and mature individuals that showed the opposite pattern. The growth characteristics were estimated by LS frequency analysis. For females, the best fitting models gave a mean birth date in August, during the height of the breeding cycle, with the following von Bertalanffy growth function parameters: LS∞ = 153·3, K = 0·29 and t0 =– 0·37 years. For males, the best fitting model gave a mean birth date in July, also during the height of the breeding period, with LS∞ = 142, K = 0·30 and t0 =– 0·36 years. At a given age, females were systematically larger than males and the size difference increased with age. The largest females sampled (148 cm LS) was 11 years old and the largest male (134 cm LS) was 9 years old. The mortality estimates were higher for males total (Z) = 1·34, natural (M) = 0·52 and fishing (F) = 0·82 than for females (Z = 0·98, M = 0·50, F = 0·48). The life‐history patterns of B. rousseauxii are discussed in light of the available knowledge about this species and the understanding of its complex life cycle. 相似文献
13.
Reproductive parameters of the Pacific angel shark Squatina californica (Selachii: Squatinidae)
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A. F. Romero‐Caicedo F. Galván‐Magaña A. Hernández‐Herrera M. Carrera‐Fernández 《Journal of fish biology》2016,88(4):1430-1440
Reproductive characteristics of the Pacific angel shark, Squatina californica, were evaluated from 420 specimens obtained from the artisanal fishery in La Paz Bay, Gulf of California, Mexico. Females (99 cm, 6000 g) were larger than males (95 cm, 5000 g) in terms of both total length (LT) and body mass (MT). The overall sex ratio was significantly different from the expected 1:1, suggesting sexual segregation of mature individuals in La Paz Bay. Males had developed reproductive organs and calcified claspers from 72 cm LT; the median size at maturity (LT50) was 75·6 cm. In females, only the left ovary was functional and mature ovarian follicles were present from 77 cm LT; the estimated LT50 was 77·7 cm. For the 10 gravid females sampled, uterine fecundity was between two and 10 embryos. Mature, non‐gravid females with small and large ovarian follicles appeared simultaneously with gravid females with follicles that did not exceed 1·9 cm diameter. 相似文献
14.
Reproductive parameters of rhinobatid and urolophid batoids taken as by‐catch in the Queensland (Australia) east coast otter‐trawl fishery
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P. M. Kyne A. J. Courtney I. P. Jacobsen M. B. Bennett 《Journal of fish biology》2016,89(2):1208-1226
Reproductive variables are provided for batoids regularly taken as by‐catch in the east coast otter‐trawl fishery on the inner‐mid continental shelf off the south‐east and central coasts of Queensland, Australia. Total length at maturity (LT50 and 95% c.i .) for the eastern shovelnose ray Aptychotrema rostrata was 639·5 mm (617·6–663·4 mm) for females and 597·3 mm (551·4–648·6 mm) for males. Litter size (n = 9) ranged from nine to 20 (mean ± s.e. = 15·1 ± 1·2). This species exhibited a positive litter size–maternal size relationship. Disc width at maturity (WD50 and 95% c.i .) for the common stingaree Trygonoptera testacea was 162·7 mm (155·8–168·5 mm) for females and 145·9 mm (140·2–150·2 mm) for males. Gravid T. testacea (n = 6) each carried a single egg in the one functional (left) uterus. Disc width at maturity (WD50 and 95% c.i .) for the Kapala stingaree Urolophus kapalensis was 153·7 mm (145·1–160·4 mm) for females and 155·2 mm (149·1–159·1 mm) for males. Gravid U. kapalensis (n = 16) each carried a single egg or embryo in the one functional (left) uterus. A single female yellowback stingaree Urolophus sufflavus carried an embryo in each uterus. A global review of the litter sizes of shovelnose rays (Rhinobatidae) and stingarees (Urolophidae) is provided. 相似文献
15.
K. V. Akhilesh K. K. Bineesh W. T. White C. P. R. Shanis M. Hashim U. Ganga N. G. K. Pillai 《Journal of fish biology》2013,83(5):1112-1127
Fishery and biological data are presented for the poorly known bramble shark Echinorhinus brucus (Squaliformes: Echinorhinidae), from the deep waters of the south‐eastern Arabian Sea. A total of 5318 individuals from by‐catch landings of deep‐water bottom set longlines, gillnets and shrimp trawl fisheries operating at depths of 200–1200 m were recorded between January 2008 and December 2011 at the Kochi Fisheries Harbour (Kerala). A total of 431 individuals, from 46 to 318 cm total length (LT) and 0·8 to 132 kg total mass (MT), were examined to determine biological data for this species. The LT at which 50% were mature (LT50) for females and males was estimated at 189 and 187 cm LT. Litter size ranged from 10 to 36 and size at birth was between 42 and 46 cm LT. Dietary analysis of stomach contents revealed E. brucus feeds on a variety of prey including crustaceans (69% index of relative importance, IRI), teleosts (25·8% IRI), cephalopods (1·7% IRI) and elasmobranchs (0·7% IRI). This study provides the first detailed biological data for this species and also highlights the extent of the by‐catch fishery for this species in Indian waters. 相似文献
16.
P. Oliveira F. H. V. Hazin F. Carvalho M. Rego R. Coelho A. Piercy G. Burgess 《Journal of fish biology》2010,76(7):1655-1670
From February 2005 to September 2007, a total of 490 crocodile sharks Pseudocarcharias kamoharai, caught as by‐catch in the swordfish and tuna longline fishery that operates in the tropical western Atlantic Ocean, was studied in regard to their reproductive biology. Maximum observed total lengths (LT) were 1220 and 1090 mm for females and males respectively, with a high proportion of the catch being composed of mature specimens. Sexual maturity was attained at 760–810 mm LT for males (LT50 = 800 mm) and 870–980 mm LT for females (LT50 = 916 mm). The size at birth was estimated at 415 mm LT. Temporal variation in gonad morphology and mass suggests that in this region P. kamoharai, an aplacental viviparous species with oophagy, does not show a well‐defined reproductive seasonality, with mating and parturition occurring possibly over an extended period of the year. Mean ±s.d . fecundity was estimated to be 3·9 (± 0·6) pups per reproductive cycle. 相似文献
17.
A. M. Cicia W. B. Driggers III G. W. Ingram Jr. J. Kneebone P. C. W. Tsang D. M. Koester J. A. Sulikowski 《Journal of fish biology》2009,75(7):1648-1666
Size and age estimates at sexual maturity were determined for 162 male and 273 female little skates Leucoraja erinacea collected from the western Gulf of Maine. Maturity ogives suggest that 50% maturity in females occurs at age 9·5 years and 480 mm total length (LT), whereas 50% maturity in males occurs at a slightly younger age of 7·7 years and smaller size of 460 mm LT. Age estimates were made from 389 L. erinacea ranging in size from 93 to 570 mm LT. The index of average per cent error and age‐bias plots indicated that the ageing methods were precise and non‐biased. Additionally, annual periodicity of band formation was validated with oxytetracycline in eight individuals (three males and five females) ranging in age from 3 to 12 years. In conclusion, results from this study indicate that L. erinacea exhibits characteristics that make other elasmobranch populations highly susceptible to overexploitation. 相似文献
18.
During a survey of the population of blacktip reef shark Carcharhinus melanopterus in Moorea (French Polynesia) between 2007 and 2011, population structural characteristics were estimated from 268 individuals. Total length (LT) ranged from 48 to 139 cm and 48 to 157 cm for males and females, respectively, demonstrating that the average LT of females was larger than that of males. The C. melanopterus population at Moorea showed an apparent spatial sexual segregation with females preferentially frequenting lagoons and males the fore‐reefs. Mean growth rate was c. 6 cm year?1. Males reached sexual maturity at 111 cm LT. This study reports on the population characteristics of this widespread carcharhinid shark species and makes comparisons with other locations, confirming high geographic variability in the population structure of the species. 相似文献
19.
C.‐N. Tsai W.‐C. Chiang C.‐L. Sun K.‐T. Shao S.‐Y. Chen S.‐Z. Yeh 《Journal of fish biology》2014,84(2):354-371
To examine trophic dynamics over different size classes, an isotopic study of sailfish Istiophorus platypterus life‐history stages was carried out. Samples were collected from eastern Taiwan and the South China Sea during April 2009 and February 2012. A total of 263 samples (111–245 cm, lower jaw fork length, LLJFL) were examined for changes in trophic structure in relation to LLJFL by using stable isotope analysis of carbon (δ13C) and nitrogen (δ15N). The δ15N values for I. platypterus ranged from 7·51 to 14·19‰ (mean ± s.d . = 12·06 ± 1·16‰) and the δ13C values ranged from ?22·04 to ?15·48‰ (mean ± s.d . = ?17·62 ± 1·10‰). The δ15N values were positively dependent on LLJFL (r2 = 0·377), whereas δ13C were negatively dependent on LLJFL (r2 = 0·063). There were significantly different seasonal changes in nitrogen and carbon isotopic concentration, but no significant differences in concentrations between eastern Taiwan and the South China Sea were reported. The trophic level (TL) of each LLJFL class was correlated, starting from 2·84 TL for size class I (LLJFL < 140 cm) and reaching 5·03 TL for size class VI (LLJFL > 221 cm). The mean ± s.d . TL was 4·43 ± 0·19 for all samples. The results reveal that I. platypterus occupies a wide range of trophic levels and different size classes occupy different trophic positions in the pelagic ecosystem. 相似文献
20.
Life-history traits of kite skates Dipturus chilensis were examined from two regions (c. 2286 km apart) in the sheltered fjords and channels of southern Chile. A total of 482 and 403 specimens were collected from the southern fjords (c. 42–46° S) and the fjords of Chilean Patagonia (c. 51–54° S), from September 2003 to 2004, respectively. Vertebra marginal increment analysis indicated an annual deposition of growth rings which was completed during the winter months. For each region, von Bertalanffy growth parameters showed that females attained a larger asymptotic size, L∞, had a lower growth coefficient, K, and lived longer than males. Growth analysis indicated that D. chilensis from the Patagonian fjords had a longer life span (females: 22 v. 21 years; males 19 v. 17 years), attained a larger L∞ (females: 150 v. 136 cm; males: 122 v. 118 cm total length, LT) and had a lower K value (females: 0·087 v. 0·104; males: 0·110 v. 0·116) than their counterparts in the southern fjords. Comparisons with previous studies indicated that D. chilensis from both southern and Patagonian sheltered fjords had larger L∞, and grew more slowly than their counterparts from central-southern Chile (L∞= 119–123 cm, K= 0·123–0·127), suggesting latitudinal variations in growth. Females attained sexual maturity later than males in both regions. For both sexes, lengths at 50% maturity (L50%) between regions were similar (females: c. 103 cm; males: c. 87 cm LT); however, D. chilensis from Patagonia appeared to mature 1 year earlier (females: 13 v. 14 years; males: 10 v. 11 years). Specimens from Patagonia had a lower ovarian fecundity than those from the southern fjords. An increase in the proportion of mature females and males during summer, suggests that the reproductive peak occurs in this season, and no regional differences were found. The size of the egg cases increased with maternal LT and these were longer in Patagonia. The information provided here represents the first evidence of regional variations in life-history traits for elasmobranchs in the south-eastern Pacific. 相似文献