Validated age and growth of the leopard shark,Triakis semifasciata,with comments on reproduction

Synopsis The age, growth, and sexual maturation of the leopard shark, Triakis semifasciata, from central California were studied. Growth band counts in vertebral centra of 162 leopard sharks produced von Bertalanffy growth curves with L, K. and t_o parameters of 1536 mm. 0.082, and -2.31, respectively, for both sexes combined. The L₈ value for females (1602 mm TL) was slightly but insignificantly higher than for males (1499 mm TL), but the K and t_o values were almost identical. Seasonal changes in size modes of young-of-the-year leopard sharks, centrum edge characteristics, and growth and tetracycline mark-recapture from the field were used to validate annual deposition of vertebral centrum band pairs. Sexual maturity was evaluated by the gonads and presence of sperm and eggs; males mature at 7 yr and at about 63% of asymptotic length, and females mature at 10 yr, and at about 72% of asymptotic length. This slow growth, late maturity, and relatively low fecundity may increase their susceptibility to over-exploitation.     

Age and growth of the sandbar shark, Carcharhinus plumbeus, in Hawaiian waters through vertebral analysis

Age and growth estimates were determined for the sandbar shark, Carcharhinus plumbeus, from Oahu, Hawaii in the central Pacific Ocean. Age estimates were obtained through vertebral centra analysis of 187 sharks. We verified our age estimates through marginal increment analysis of centra and oxytetracycline marking methods of at liberty sandbar sharks. Sizes of sampled sharks ranged from 46 to 147 cm pre-caudal length. Four growth models were fitted to length-at-age data; two forms of the von Bertalanffy growth model, the Gompertz growth model, and a logistic growth model. Males and females exhibited statistically significant differences in growth, indicating that females grow slower and attain larger sizes than males. Growth parameter estimates revealed slower growth rates than previously estimated (based on captive specimens) for Hawaiian sandbar sharks. The von Bertalanffy growth model using empirical length-at-birth provided the best biological and statistical fit to the data. This model gave parameter estimates of L _∞ = 138.5 cm PCL and k = 0.12 year⁻¹ for males and L _∞ = 152.8 cm PCL, k = 0.10 year⁻¹ for females. Male and female sandbar sharks mature at approximately 8 and 10 years of age, respectively.     

A re-examination of the age and growth of sand tiger sharks, Carcharias taurus, in the western North Atlantic: the importance of ageing protocols and use of multiple back-calculation techniques

Age and growth estimates for sand tiger sharks, Carcharias taurus, in the western North Atlantic were derived from 96 vertebral centra collected from sharks ranging from 94 to 277 cm total length (TL), and compared to previously published age and growth data. The oldest female and male sand tiger sharks aged in this study were 17 and 15 years of age, respectively. von Bertalanffy growth parameters derived from vertebral length-at-age data are L _∞ = 295.8 cm TL, k = 0.11 year⁻¹, and t ₀ = −4.2 years for females, and L _∞ = 249.5 cm TL, k = 0.16 year⁻¹, and t ₀ = −3.4 years for males. Sexual maturity is estimated to be 9–10 years for females and 6–7 years for males. Weight-to-length relationships determined for female and male sand tiger sharks in the western North Atlantic are; W = 1.3 × 10⁻⁴ × L ^2.4 (r ² = 0.84, n = 55) and W = 9.0 × 10⁻⁵ × L ^2.5 (r ² = 0.84, n = 47), respectively, and 7.9 × 10⁻⁵ × L ^2.5 (r ² = 0.84) for the sexes combined. Our results show sand tigers possess a slower rate of growth than previously thought. This information is crucial for accurately assessing this population’s ability to recover, and further justifies the need for this species to be fully protected.     

Age and growth estimates of the bull shark,Carcharhinus leucas,from the northern Gulf of Mexico

Synopsis Length at age and growth rates for 59 bull sharks, Carcharhinus leucas, collected from the northern Gulf of Mexico were estimated from the band patterns formed seasonally in the vertebral centra. The combined age at length data for both sexes were applied to a von Bertalanffy growth model producing parameter estimates of L = 285 cm TL, K = .076, t₀ = –3.0 yr. Lengths at age for males and females were similar except that males did not attain as great a length as females. Growth was apparently slow and varied among individuals, but in general, was estimated to be 15–20 cm yr^–1 for the first five years, 10 cm yr^–1 for years 6–10, 5–7 cm yr^–1 for years 11–16, and less than 4–5 cm yr^–1 thereafter. Males mature at 210–220 cm TL or 14–15 yr of age; females mature at>225 cm TL or 18+ yr of age. The largest male (245 cm TL) was 21.3 yr old; the largest female (268 cm TL) was 24.2 yr old.     

Age, growth and reproduction of the humpback red snapper Lutjanus gibbus off Ishigaki Island, Okinawa

The humpback red snapper Lutjanus gibbus (Lutjanidae) is an important species for fisheries in the Kagoshima and Okinawan region of Japan. The present study estimated the age, growth and reproduction of this lutjanid species in the waters around Ishigaki Island, southern part of Okinawa. An opaque zone was formed on the otolith every year, and this formation correlated with their spawning season; these zones were identified as annual rings. Maximum ages of 21 and 24 years were observed for males and females, respectively. The von Bertalanffy growth parameters clarifying the age–fork length relationship were as follows: L _∞ = 390.5 mm, K = 0.210 year⁻¹ and t ₀ = −1.88 year for males, and L _∞ = 303.4, K = 0.256 year⁻¹ and t ₀ = −3.05 year for females. The main spawning season was estimated as between May and October, since greater values of gonadosomatic index for females as well as maturation oocytes and/or postovulatory follicles were observed during those six months.     

Age,growth and reproductive biology of the silky shark,Carcharhinus falciformis,and the scalloped hammerhead,Sphyrna lewini,from the northwestern Gulf of Mexico

Synopsis The silky shark, Carcharhinus falciformis, and scalloped hammerhead, Sphyrna lewini, represent >80% of the shark by-catch of the winter swordfish/tuna longline fishery of the northwestern Gulf of Mexico. This catch represents a potential supplemental fishery, yet little is known of the life histories of the two species. This report relates reproductive biology data to age and growth estimates for 135 C. falciformis and 78 S. lewini. Unlike other regional populations, C. falciformis in the Gulf of Mexico may have a seasonal 12 month gestation period. Males mature at 210–220 cm TL (6–7 yr); females at >225 cm TL (7–9 yr). Application of age at length data for combined sexes produced von Bertalanffy growth model parameter estimates of L_∞ = 291 cm TL, K = 0.153, t₀ = −2.2 yr. Adult male S. lewini outnumbered adult females in catches because of differences in the distributions of the sexually segregated population. Males mature at 180 cm TL (10 yr); females at 250 cm TL (15 yr). von Bertalanffy parameter estimates for combined sexes of this species were L_∞ = 329 cm TL, K = 0.073, t_o = −2.2 yr.     

Length-based growth,maturity and natural mortality of the cockfish <Emphasis Type="Italic">Callorhinchus callorhynchus</Emphasis> (Linnaeus, 1758) off Coquimbo,Chile

The growth rate, reproductive aspects, and natural mortality of chimaeras and ratfish are poorly known. In this study, life-history parameters for cockfish Callorhinchus callorhynchus (Holocephali—Callorhinchidae) are estimated, which is an important fish resource exploited in Chile. Specimens were sampled from the artisanal fishery captures, from November 2006 to November 2007. The standard length (SL) of males fluctuated between 20 and 62 cm, and between 21 and 70 cm for females. Von Bertalanffy growth parameters were estimated through length-frequency data analysis using MULTIFAN. The length-weight relationship and von Bertalanffy growth parameters were significantly different for males and females, as well as the length at 50% maturity. For males a model with 5 age-classes was the best, with asymptotic length L _∞ = 52 cm SL, growth coefficient K = 0.473 yr⁻¹, and age at length zero t ₀ = −0.690 yrs. For females the best model was represented by 10 age-classes (L _∞ = 70.3 cm SL, K = 0.193 yr⁻¹, t ₀ = −1.158 yrs) in the length-frequency data sets. Length at 50% maturity of males was estimated in 43.7 cm SL, and in 50.2 cm SL for females. The natural mortality rate fluctuated between 0.42 and 0.82 yr⁻¹ for males and between 0.12 and 0.37 yr⁻¹ for females, depending upon the method used. It is concluded that C. callorhynchus is a species with life-history parameters significantly different between males and females, and such differences should be taken into account in future population dynamics analysis.     

Reproductive biology,growth, and age composition of non‐native Indian glassy fish Parambassis ranga (Hamilton, 1822) in Haebaru Reservoir,Okinawa‐jima Island,southern Japan

Age composition, growth, and reproductive biology of the non‐native Indian glassy fish Parambassis ranga (Hamilton, 1822) were surveyed in the Haebaru Reservoir on Okinawa‐jima Island, southern Japan. Standard lengths (SLs) of males and females ranged from 19.7 to 44.0 mm and from 19.2 to 52.4 mm, respectively. The overall sex ratio was significantly female‐biased, with the monthly percentage of females ranging from 71.4 to 100.0. Marginal growth analysis of sectioned otoliths revealed opaque zones formed annually from November to May. Observed age ranged from 0 to 3 years for both sexes, although the 1‐year age class comprised the majority of the sampled population. Von Bertalanffy growth parameters were L_∞ = 48.8 mm (SL), K = 0.43 year^?1, and t₀ = ?1.47 years for males, and L_∞ = 43.7 mm, K =0.72 year^?1, and t₀ = ?1.29 years for females. Length at 50% maturity was estimated to be 25.8 mm SL, and maturation was within 1 year after hatching. The main spawning season of P. ranga was estimated to occur from February to October, peaking in April.     

Preliminary observations on the life history of the white-streaked grouper, <Emphasis Type="Italic">Epinephelus ongus</Emphasis>, from Okinawa,Japan

A preliminary analysis of 175 specimens of the white-streaked grouper, Epinephelus ongus (Serranidae), was undertaken to determine life history characteristics of the species. Sagittal otoliths, stomachs, and a subsample of gonads were removed to determine age at length, diet, and reproductive strategy. The von Bertalanffy growth equation was used to describe growth in this species and yielded the growth parameters L^∞ = 438.3, K = 0.04334, and t₀ = −8.752. Fish ranged in age from 1 to 20 years. Diet was consistent with other serranid species and included crabs, shrimps, octopi, and fishes. Based on a very limited number of specimens (n = 12), the larger size and older age of males compared to females suggests that E. ongus may be a protogynous hermaphrodite.     

Age and growth of the blacknose shark, <Emphasis Type="Italic">Carcharhinus acronotus</Emphasis>, in the western North Atlantic Ocean with comments on regional variation in growth rates

We examined the age and growth of the blacknose shark, Carcharhinus acronotus, in the western North Atlantic Ocean by obtaining direct age estimates using vertebral centra. We verified annual deposition of growth increments with marginal increment analysis and validated it by analyzing vertebrae marked with oxytetracycline from a female blacknose shark held in captivity. Von Bertalanffy growth parameters indicated that female blacknose sharks have a lower growth constant (k), a larger theortical maximum size (L), and are longer lived than males. We compared these growth parameters for blacknose sharks in the western North Atlantic Ocean to growth parameters for blacknose sharks collected in the eastern Gulf of Mexico to test for differences between regions. Females in the western North Atlantic Ocean have a significantly lower L, lower k, and a higher theoretical longevity than females in the Gulf of Mexico. Males in the western North Atlantic Ocean have a higher L<>, lower k, and higher theoretical longevity than males in the Gulf of Mexico. The significant differences between these life history parameters for blacknose sharks suggest that, when possible, future management initiatives concerning blacknose sharks should consider managing the populations in the western North Atlantic and the Gulf of Mexico as separate stocks.     

Age,growth, and reproductive biology of blacktail snapper,Lutjanus fulvus,around the Yaeyama Islands,Okinawa, Japan

Age, growth, and reproductive characteristics of blacktail snapper, Lutjanus fulvus, which is a commercial fish species, were investigated using 322 specimens (40–332 mm in fork length) caught around the Yaeyama Islands, Okinawa, Japan. Spawning season was estimated to be from April to October, and spawning was confirmed around the full moon and the last quarter moon. Age determination using sectioned otoliths revealed that ages ranged from 0 to 34 years and the majority was ≥ 3 years. Parameters of the von Bertalanffy growth function were estimated to be L _∞  = 270 mm, k = 0.40, and t ₀  = ?0.48 years for females, and 257 mm, 0.44, and ?0.42 years for males. Initial growth was rapid during the first 3 years, attaining over 200 mm for both sexes, and then females grew larger than males. Sizes (ages) at the first sexual maturity were 225 mm (4 years) for females and 207 mm (3 years) for males. The wide range of age composition in catch with majority of ≥3 years old implied that the current fishing effort to harvest was not sufficiently large enough to collapse the stock immediately.     

Age and growth of Schizopygopsis younghusbandi younghusbandi in the Yarlung Zangbo River in Tibet, China

Schizopygopsis younghusbandi younghusbandi is an endemic species whose distribution is restricted to the middle reaches of the Yarlung Zangbo River, being one of the most important commercial fishes in this area. Age and growth of 606 specimens captured between October 2002 and April 2005 were studied. The range in standard length (L) was 65.7–387.3 mm and total weight (W) was 3.3–772.0 g. The relationship between L and W was W = 0.000909L^2.2493 for males and W = 0.000259L^2.4781 for females. Age, determined from anal scales and lapillus otoliths, ranged from 3 to 18 years. The parameters of von Bertalanffy growth functions, estimated by back-calculated length, were L_￥ = 442.7mm  LL_\infty = 442.7mm\;L, k = 0.0738 year⁻¹ and t ₀  = −1.4 year for males, and L_￥ = 471.4mm  LL_\infty = 471.4mm\;L, k = 0.0789 year⁻¹ and t ₀ = 0.2 year for females. Males and females exhibited statistically significant differences in growth. χ ²-test indicated that von Bertalanffy growth functions could well describe the growth of S. y. younghusbandi. The longevities were 39.2 and 38.2 years for males and females, respectively. Growth inflexion points were 10.2 and 12.0 years for males and females, respectively, but 84.8% of the captures were at the smaller ages. So conservation and management schemes for this population should be considered urgently. In addition, we found that populations from the upstream of the Lhasa River, the downstream of the Lhasa River and the middle reaches of the Yarlung Zangbo River showed statistically significant differences in growth patterns.     

Age and growth of the nototheniid fishTrematomus bernacchii Boulenger from Terra Nova Bay,Antarctica

Age and growth of the nototheniid fishTrematomus bernacchii Boulenger 1902 were estimated by reading the sagittal otoliths of 457 adult specimens caught off Terra Nova Bay (Ross Sea) in the austral summer 1990–1991. Annuli in ground and polished otoliths were examined using a dissecting microscope under reflected light. The Von Bertalanffy growth equation was L_t=273.5 [1 − e^{−0.109(t+2.10)}] for males (n=122) and L_t=422.2 [1 − e^{−0.055(t+1.92)}] for females (n=211) where L is total length in millimetres. Maximum estimated age was 21 years for females and 16 years for males. This is in agreement with the hypothesis that considers slow growth and old age as a typical feature of Antarctic fishes.     

Age and growth of the Australian sharpnose shark,Rhizoprionodon taylori,from north Queensland,Australia

Synopsis Age and growth were studied inRhizoprionodon taylori using specimens caught in Cleveland Bay, North Queensland, Australia. Von Bertalanffy growth parameters were estimated using three different techniques: vertebral ageing, back calculation and length frequency. Vertebrae from 138 specimens were sectioned and narrow circuli counted to estimate age. Marginal increment analysis verified that circuli were produced annually in late summer, probably as a result of stress during the mating season. The oldest female was 7 and male 6 years old. Von Bertalanffy growth parameters estimated from vertebral ageing data for males were t_O = 0.410 yr, K = 1.337, L = 652.2 mm, and for females t_O = 0.455 yr, K = 1.013 and L = 732.5 mm. Growth parameters determined by length frequency and back calculation techniques concurred with those from vertebral ageing. Growth of the 0+ age class was very rapid, averaging 140% of the size at birth in the first year. Males and females matured after only one year, the lowest age at maturity reported in the family Carcharhinidae. Annual growth increments decreased rapidly after maturity, and little growth occurred after three years.     

Age,growth and reproduction of a population of spined loach,Cobitis taenia (L.)

751 specimens of spined loach, Cobitis taenia (L.), were collected and studied over the period October 1972–October 1974. The majority of the males were found to die at the end of the 2+ season and the majority of the females at the end of the 3+ season. Back calculations for length at age were carried out from otolith measurements and found to correspond closely to actual measurements. Males and females grew similarly up until the end of their 1+ year of life, with most rapid growth occurring in the first year. Females continued to grow rapidly up to 2+, the rate then being reduced; the males showed an increasingly reduced rate of growth after the 1+ year. Ford Walford plots gave L∞ results which corresponded closely in most cases with the largest observed specimens. Gonad development and maturation of males and females followed different patterns. Males matured during the 1 + year at a length of approximately 40 mm from which point their dry gonad weight remained at a steady 0.02–0.03% of the body weight. Females appeared to mature a year later and their ovary weight and oocyte diameter increased with fish age. A seasonal cycle in gonad development was evident in females. There was a greater proportion of females to males, especially in the older age group. Spawning time was estimated to be between June and July.     

Age, Growth Rates, Sex Change and Feeding Habits of Notothenioid Fish Eleginops Maclovinus from the Central-southern Chilean Coast

The róbalo, Eleginops maclovinus, a protandrous hermaphrodite species, is an important component of the ichthyofauna in the coastal areas and estuaries of southern Chile. However, there are many aspects about its life history that are unknown. Three hundred and eighty-three specimens of E. maclovinus (19–79 cm total length, TL) were collected between November 2002 and December 2003 from central-southern Chile. Marginal increment analysis from sagittal otoliths showed a single annual minimum in March, demonstrating that a single growth ring is formed each year. The growth of E. maclovinus was described by the von Bertalanffy growth model by following parameters: L _∞ = 105.4 cm TL, K = 0.08 per year, and t ₀ = −1.03 years. E. maclovinus can live for 10 years. The length and age at which the 50% of the males in the population transformed into females was estimated at ~36 cm TL and ~5-years old. A total of 27 prey items were identified. The most important prey items were the crustaceans Hemigrapsus crenulatus and Emerita analoga associated with estuarial and marine habitats respectively. Ontogenetic changes in the diet were related to the spatial distributional pattern of males (1–4 years old, in the estuary) and females (5–8 years old, in the sea). Also, diet changes are associated with the type of available prey in each habitat occupied, indicating a generalized opportunist strategy.     

Sexual size dimorphism,growth, and maturity of the fluvial eight-barbel loach in the Kako River,Japan

The maturation and growth pattern of the fluvial eight-barbel loach Lefua sp. (Japanese name: nagare-hotoke-dojo), an endangered species, was investigated using an individual identification-recapture method from 1995 to 1998 in an upper reach of a headwater tributary of the Kako River, Hyogo Prefecture, Japan. Based on observations of the gonads through the abdominal skin, the loach was estimated to breed mostly from May to July. All the males matured by age 1⁺, and all the females matured by age 2⁺. Gamete release in all individuals of both males and females was predicted from recaptured loaches during each breeding season. The standard length of mature females was significantly larger than that of males, showing sexual size dimorphism (SSD). The maximum sizes recorded were 75.4 mm SL for females and 61.2 mm SL for males. Both males and females of immature specimens grew mainly from May to November, including the breeding season, with no significant differences in growth rates between them. After sexual maturity, both males and females grew mainly from July to October (or November), after the breeding season, and the females exhibited higher growth rates than males. Therefore, SSD of the species seems to be attributable to the different growth rates after maturity. The longevity of the loach was estimated to exceed ten years based on individual growth patterns of various sizes during the survey period. It is likely that the loach has an iteroparous life history, breeding every year, and moderate growth rates after maturity.     

Age and growth of the roughtail skate Bathyraja trachura (Gilbert 1892) from the eastern North Pacific

This study provides the first published age estimates for the roughtail skate, Bathyraja trachura. Age and growth characteristics of B. trachura, a poorly-known deepwater species, were determined from samples collected along the continental slope of the contiguous western United States. A new maximum size was established at 91.0 cm TL. Age was determined using a traditional structure (vertebral thin sections) with widespread application on multiple skate species and a non-lethal structure (caudal thorns) recently used for age analysis on skate species. Caudal thorns were determined not to be a useful ageing structure for this species based on poor precision and significantly lower age estimates when compared to age estimates from vertebral thin sections. The best model for describing growth of B. trachura was the two parameter VBGF, assuming annual vertebral band deposition and using length-at-age data. Although females grew slower and reached a larger maximum size than males, their growth was not statistically different (ARSS; P = 0.90); therefore, data were pooled (L_∞ = 99.38, k = 0.09). Annual band deposition was found to be a reasonable assumption for this species, but has yet to be validated. The maximum age estimated for B. trachura was 20 years for males and 17 years for females using vertebral thin sections.     

Life history characteristics of the protogynous parrotfish Calotomus japonicus from northwest Kyushu, Japan

In this study, we examined the life history characteristics of the parrotfish Calotomus japonicus, using individuals collected between May 2003 and May 2008 off the Nagasaki Peninsula in northwest Kyushu, Japan. Age determinations were performed using scales. Marginal increment analysis revealed that growth rings were formed annually around July. Growth in both sexes was fitted to the von Bertalanffy growth function (L _∞ = 513, k = 0.28, t ₀ = 0.03, where L _∞ is the theoretical asymptotic total length in mm, k is the growth rate coefficient and t ₀ is the theoretical time at zero length). Observed maximum age for both sexes was 8 years. We also characterized the reproductive biology of this species based on a gonadosomatic index and histological examinations of the gonads. The spawning season extends from July to October, with peak spawning activity occurring during July and August. Fish reach sexual maturity by the second year of life. Females are assumed to be multiple spawners, since we observed specimens with postovulatory follicles in ovaries containing either yolk globule oocytes or migratory nucleus oocytes. All males had secondary testes, which were characterized by the presence of an ovarian lumen structure and sperm sinuses in the gonadal wall. This indicates that all males, irrespective of whether they were initial or terminal phase males, had undergone a sexual transition. Sex change appears to occur during the spawning season, and thereafter sex-changed males are able to fertilize female eggs throughout the remainder of the current spawning season.     

Age and growth of ocellated icefish, Chionodraco rastrospinosus DeWitt and Hureau, 1979, from the South Shetland Islands

Age and growth of ocellated icefish, Chionodraco rastrospinosus, were investigated using counts of annual growth increments from sagittal otoliths. Samples were collected during research surveys by benthic trawl carried out around Elephant and South Shetland Islands in January–February 2002 and December 2006–January 2007. A total of 290 specimens were selected for the study, consisting of 120 females and 170 males. The age of fish was estimated by counting annuli on transverse sections obtained by grinding and polishing whole otoliths embedded in epoxy resin. The precision-of-age estimates within and between readers were tested applying both the average percent error (APE) and the coefficient of variation (CV). The estimated age-range was 1–12 for both sexes of C. rastrospinosus. Applying the von Bertalanffy growth function to the age–length data, a growth curve was obtained for each sex. The estimated values of VB growth parameters L _∞ and k were, respectively, 47.9 cm and 0.28 for females and 42.9 cm and 0.36 for males. Compared to other congeneric species, the growth performance of C. rastrospinosus was relatively high, being 2.82 and 2.81 in males and females, respectively. Age at sexual maturity was estimated to be about 4 years in both sexes. C. rastrospinosus captured in the studied area consisted mainly of adult specimens between 3 and 8 years, with few older fish.