Age and growth of alfonsino Beryx splendens from the Kanto District, central Japan, based on growth increments on otoliths

ABSTRACT:   Age and growth of alfonsino Beryx splendens (Lowe) were studied using counts of presumed daily incremental growth rings on the transverse section of otoliths of fish collected from the Kanto District, central Japan. Microstructural growth increments were observed from the core to the outermost margin of the broadest of approximately 50 branches formed on the surface of an otolith. Of 98 otoliths examined, 46 were readable. The number of increments and fish lengths ranged from 448 (218 mm fork length [FL]) to 3701 (411 mm FL). The ages of these fish were estimated to be 1 year, 2 months and 10 years, 2 months, respectively, assuming that an increment was formed daily. The von Bertalanffy growth equation combined for males and females was expressed as follows: L _t  = 542 {1 −  exp  [−0.133( t  + 2.00)]}, where L _t is fork length (mm) at yearly age t . The results of the present study were compared with those of other researchers who had studied alfonsino from central Japan.     

Age,growth and maturation of the redbelly tilapia <Emphasis Type="Italic">Tilapia zillii</Emphasis> introduced into the Haebaru Reservoir on Okinawa-jima Island

ABSTRACT:   The age, growth and maturation of the redbelly tilapia Tilapia zillii introduced into the Haebaru Reservoir on Okinawa-jima Island were studied using 2197 specimens ranging from 7.3 to 168.0 mm standard length (SL). The spawning season was estimated to be from April to August, with a peak in April and May. The first maturation sizes of females and males were estimated to be 38.1 and 33.0 mm SL, respectively. The opaque zones in otoliths that form annually were found to correlate with the spawning season. Maximum ages of females and males were 7 and 6 years, respectively. The von Bertalanffy growth formulae were expressed as: L _t  = 99{1 − exp[−0.67( t  + 0.09)]} for females and L _t  = 155{1 − exp [−0.36( t  + 0.12)]} for males. Males grew to be larger than females from the first year onward. Populations of this species are characterized by early maturation life history parameters and are thought to adapt and become established quickly after being released into new water systems. Furthermore, extermination activity in winter is thought to be an effective strategy before the newly recruited fish begin breeding in the warmer months.     

Age and growth of Sebastes vulpes in the coastal waters of western Hokkaido, Japan

ABSTRACT:   Age and growth of Sebastes vulpes collected from the coastal waters of western Hokkaido were studied. Observation of the otolith margin verified that annuli (outer margins of the opaque zone) were produced chiefly from July to August. This period was associated with parturition and the birth season. The maximum age estimated by the surface method was 12 years but the oldest fish was aged at 35 years by the cross-section method. The surface method was inadequate for aging of S. vulpes older than 6 years because of the underestimation of age. No significant difference was found in the parameters of the growth equations between both sexes. The von Bertalanffy growth curve combined for both sexes was as follows: SL _t  = 358.6(1 − exp^{−0.156( t +0.820)}), where SL _t is standard length (mm) at age t (after parturition in years). It seems likely that S. vulpes grows slowly and lives longer than previously thought.     

Age and growth of <Emphasis Type="Italic">Ilisha elongata</Emphasis> (Teleostei: Pristigasteridae) in Ariake Sound,Japan: comparison among populations in western North Pacific Ocean

ABSTRACT:   Elongate ilisha Ilisha elongata is a commercially important fishery resource in both Japan and China. Age and growth of the species were investigated by scale analysis from June 1996 to July 1997 in Ariake Sound, Japan. Scale annuli were formed once a year mainly between June and July. The age was 1–6 years for both male and female individuals. There was no significant difference in the regression of fork length (FL) on scale radius ( R ) between sexes by a covariance analysis. The combined sex von Bertalanffy growth equations were expressed as L _t  = 495.4 × (1 − e^{−0.3176( t  + 0.4108)}), where L _t is FL in mm at age t . Comparison of the age and growth among different populations from coastal waters in the western North Pacific Ocean suggested that the FL of the Ariake population is the smallest at each age. The spatio–temporal variations in growth are possibly relevant to environmental conditions of the growth grounds of subadults; however, there was no gradient change in the growth of I. elongata with latitude. Water temperature may not be the main factor affecting the growth of this species . The growth of the tropical population from Sarawak differs greatly from those of temperate and subtemperate populations, which implies genetic variation or phenotypic plasticity in different climate zones.     

Growth and mortality of the narrowbarred Spanish Mackerel, Scomberomorus commerson (Lacepède), in Omani waters

Length composition data from quarterly catches of Omani narrowband Spanish mackerel, Scomberomorus commerson (Lacepède), landed between 1987 and 1995 were used to estimate the growth, mortality and exploitation parameters of the stock. Non-linear least square fitting provided a complete set of von Bertalanffy growth estimates: L _∞ = 173.6 cm fork length; K  = 0.28; and t ₀ = −0.86 years. There were no seasonal differences among the growth estimates. The instantaneous natural mortalities determined by three independent methods based on life-history parameters were 0.35, 0.64 and 0.77. Seasonal total mortalities were calculated by the length converted catch curve method for evaluating seasonal exploitation ratios ( E ). The E -values exceeded 0.4, indicating overexploitation during almost all the seasons studied. This was supported by the large reduction in the total landings of S . commerson from 27 762 t in 1988 to 3265 t in 1993.     

Age, growth and reproductive characteristics of round scad Decapterus maruadsi in the waters off west Kyushu, the east China Sea

ABSTRACT:   The purpose of this study was to determine the growth and reproductive characteristics of round scad Decapterus maruadsi in the East China Sea. The characteristics regarding growth and reproduction of round scad based on otolith reading and gonad histology, respectively, were estimated. The von Bertalanffy's growth model for round scad was estimated as follows:
FL _t  = 342[1 − exp{−0.55( t  + 0.58)}], (1 <  t  < 7)
where FL _t is fork length (mm) at age in years t . The maturation stage of the ovary was observed by histological techniques. June was the main spawning period; the maturation and migratory nucleus stage of the oocyte was observed when the gonad somatic index value was approximately greater than 4.     

Age and growth of the silky shark Carcharhinus falciformis from the Pacific Ocean

ABSTRACT:   The present study estimated the age and growth of the silky shark Carcharhinus falciformis in the Pacific Ocean. Samples and biological data were collected from Japanese tuna longline and purse seine fisheries from 1992 to 1999. Vertebra centra were picked from 145 males and 153 females for age determination. The number of annual rings observed for males and females was 0–8 and 0–13, respectively. Combined sex von Bertalanffy growth equations were obtained as follows: L_t  = 216.4(1 − e^{−0.148( t +1.76)}) where L_t is precaudal length in cm at age t . A mature size for males was considered to be approximately 135–140 cm (precaudal length), with an estimated age of 5–6 years, whereas corresponding values for females were 145–150 cm and 6–7 years, respectively. Birth size ranged from 48 to 60 cm. There was no remarkable difference in growth, birth size and age at maturity between the Pacific and Atlantic Oceans. The life history parameters of the silky shark are approximately the same in both oceans.     

Target strength estimation of black porgy Acanthopagrus schlegeli using acoustic measurements and a scattering model

ABSTRACT:   Black porgy are hatched and released in marine ranching areas in Japan, Korea and Taiwan to maintain fisheries resources in coastal areas. If acoustic methods are used for field surveys, target strength ( TS ) information on the species is needed to convert acoustic data to biomass density. Target strength of black porgy ( Acanthopagrus schlegeli ) 15.5–32.9 cm fork length (nine individuals) was measured at 38 and 120 kHz (split beam) by ex situ measurements (cage and fishhook methods) of living fish, a tethered method with shock-frozen fish, and an acoustic scattering model, the Kirchhoff ray mode (KRM) model based on fish morphology. The ex situ TS -to-fork length ( FL , cm) relationships were TS _38kHz = 20log₁₀ FL  − 64.6 ( r  = 0.77) and TS _120kHz = 20log₁₀ FL  − 65.2 ( r  = 0.70). The values for the KRM model were TS _38kHz = 20log₁₀ FL  − 64.8 ( r  = 0.88) and TS _120kHz = 20log₁₀ FL  − 65.4 ( r  = 0.80). The agreement between the ex situ measurements and the KRM model for the mean TS was very good. In contrast, the results for the tethered method ( TS _38kHz = 20log₁₀ FL  − 69.3 [ r  = 0.42]) differed markedly from the other two methods, perhaps because of the effects of the shock-freezing procedure in air. The results of the ex situ measurements and scattering model provide basic information for studying TS and conducting acoustic surveys of black porgy, even though the tethered method must be modified.     

Growth and spawning of hatchery-reared Chinese white prawn Penaeus (Fenneropenaeus) chinensis released in the Ariake Sea, Japan

SUMMARY: Growth and reproduction of hatchery-reared Chinese white prawn Penaeus chinensis released in the Ariake Sea, Japan, were examined. Chinese white prawn grew rapidly, reaching a body length of 154 mm in males and 198 mm in females by November (219–229 days after hatching). Maximum body length of sampled individuals was 164 mm in males and 223 mm in females. Growth curve of the Chinese white prawn was fitted to the Pitcher and MacDonald's formula, L_t = 155.0{1 − e ^{2.925sin[2π(t − 16.151)/365] − 0.0623( t − 10.712)}} for males and the logistic curve, L_t = 200.3/[1 + e ^{(1.985–0.034 t )}] for females (where L_t is the body length t days after release and t is the number of days after release). Females reached sexual maturity in late February and spawning occurred until April. Minimum size at ripe and spawned stages was 189 mm and 193 mm body length, respectively.     

Effects of entrance design on catch efficiency of arabesque greenling traps: a field experiment in Matsumae, Hokkaido

ABSTRACT:   A field experiment was conducted in the Matsumae area of Hokkaido, Japan, during June and July 2002, to investigate the effects of different entrance designs on the catch efficiency of fish traps by fishing with commercial traps (entrance inclination angle [α] = 37°; funnel length of entrance [ L _f ] = 22 cm) and experimental traps. The experimental traps were of the same size and similar design as commercial traps, with different entrance inclination angles (trap E1: α = 46°; E2: α = 27°; E3: α = 0°; all L _f  = 22 cm) or funnel lengths (E4: α = 37°, L _f  = 8 cm). In total, 2200 fish during 200 trap hauls were captured. The catch was significantly higher using both traps E2 and the commercial trap than with trap E3 ( P  < 0.05), and the catch of trap E2 was higher than that of the commercial trap. There were no significant differences in mean fish body length or the frequency distributions of body length among trap types (E1, E2, E3 and commercial). The funnel length of the entrance also affected the catch of traps. Trap E4 had significantly higher catches than the commercial trap ( P  = 0.04) when traps were deployed for a 1-day soak time. Fish body length frequency distributions did not differ between trap E4 and the commercial trap. The results showed that catch can be greatly affected by trap entrance designs.     

Age,growth and maturation of the blackspot snapper <Emphasis Type="Italic">Lutjanus fulviflammus</Emphasis> around Okinawa Island,Japan

ABSTRACT:   The blackspot snapper Lutjanus fulviflammus is one of the most common Lutjanus species landed and consumed on Okinawa Island, Japan. Using 901 fish (29.9–304.2 mm in standard length; SL) obtained from fish markets or caught by angling, the age, growth, maturation size and maturation age were estimated. Each opaque zone formed on the otolith every year correlated with their spawning and was thought to be an annual ring. The main spawning season was estimated to be from April to July, which peaked in May and June, with a few mature fish collected in August and September. Maximum ages were observed as 24 years for both sexes and L_∞ (mm SL), K and t₀ (years) of the von Bertalanffy growth formula were estimated to be 276, 0.144 and −5.22 for females and 247, 0.227 and −3.18 for males, respectively. First maturation size and age were estimated to be 175 mm SL and 2 years for both sexes. A faster growth rate up to 2 years will allow reproduction at a young age and provide many chances for spawning throughout their long life. Furthermore, the possibility exists that populations would easily recover if regulations were established.     

Induction of interspecific allo-tetraploids of Megalobrama amblycephala♀×Megalobrama terminalis♂ by heat shock

Interspecific allo-tetraploidy was induced by a combination of hybridization of Megalobrama amblycephala ♀× Megalobrama terminalis ♂ and thermal shock. A thermal shock at 40 °C for 2 min applied to eggs 33 or 26 min (τ₀: 1.40) after fertilization resulted in a significantly ( P <0.01) higher yield of allo-tetraploids than hybrid crosses without heat shock. The yield of allo-tetraploids in embryos from mid-gastrula to hatching stages was 15.7–24.4% in different thermal shock treatment groups. The allo-tetraploidy rate in 330-day-old juveniles was 9.3% and 6.7% in different year treatment groups. After 2 years of rearing, allo-tetraploidy males attained sexual maturity with milk-like milt at the age of 2+, while allo-tetraploidy females at the age of 2+, and even at 3+, did not show any signs of sexual maturation exhibiting obviously delayed maturity. Only a few allo-tetraploidy females (three individuals) showed maturation characters at the age of 4+ and these females were induced to spawn.     

Age, growth, and reproduction of silky sharks, Carcharhinus falciformis, in northeastern Taiwan waters

To examine the age, growth and reproduction of silky sharks, Carcharhinus falciformis, in the waters off northeastern Taiwan, 469 specimens (213 females and 256 males) were collected from August 2000 to January 2002 at the Nanfanao fish market, northeastern Taiwan. The relationship between body weight (W) and total length (TL) for both sexes combined was expressed as: W = 2.92 × 10⁻⁶ TL^3.15 (n = 469, p < 0.01). The relationship between TL and vertebral centrum radius (R) for both sexes combined data was estimated as: TL = 25.979 + 18.197R (n = 250, p < 0.01). Growth bands (including translucent and opaque zones) in precaudal vertebrae formed once a year between December and January and were counted up to 11 and 14 for females and males, respectively. The von Bertalanffy growth function (VBGF) was used to model the observed length at age data. The sexes combined VBGF predicted an asymptotic length (L_∞) = 332.0 cm TL, growth coefficient (k) = 0.0838 year⁻¹, age at zero length (t₀) = −2.761 year (n = 250, p < 0.01). Size at 50% maturity for males was estimated to be 212.5 cm based on the logistic curve, which corresponded to 9.3 years. Females matured at 210–220 cm, which correspond to 9.2–10.2 years. The length at birth was estimated to be 63.5–75.5 cm TL. The number of embryos per litter was 8–10 and sex ratio of embryos was 1:1.     

Growth, population composition and reproduction of Bream Abramis brama (L.) in Lake Volvi, Macedonia, Greece

Abstract– Growth, population composition and reproduction of bream were studied in Lake Volvi from 1989 to 1991. Females had a higher growth in length (L_∞=507 mm, k=0.094) than males (L_∞=452 mm, k=0.102). Growth can be characterized as medium, due to low food sources (zooplankton and chironimids). Large specimens are scarce because of high fishing mortality and low growth rate. All males greater than three years old, longer than 135 mm and all females greater than four years old and longer than 150 mm were sexually mature. These values of age and size of first maturity are the lowest that have been reported for this species. The size of the spawning egg is independent of the body size.     

Estimate of reproductive value of the big eye Priacanthus macracanthus in the north-eastern waters off Taiwan

ABSTRACT: The reproductive value and population status of the big eye in the north-eastern Taiwan waters was estimated by demographic analysis using available life-history parameters. Life-history tables were constructed using estimates of natural mortality ( M ) of 10.4920/year for age 0 and 0.3256/year for ages 1–9, with a maximum age of 9. Age-specific batch fecundity ( F_e ) was from F_e  = 1391.34e^{0.1782 FL} . The age-specific proportion of maturity was estimated from the relationship between the proportion of female maturity ( Pr ) and fork length ( FL ): Pr  = 1/(1 + e^{15.081−0.796 FL} ). Females mature at age 3 and mature females reproduce every year. The population increase rate (λ) was estimated to be 20.5% per year and the generation time ( G ) was 6.25 years without exploitation. The net reproductive value ( R₀ ), generation time and intrinsic rate of natural increase ( r ) decreased with increased fishing mortality. For fixed fishing mortality, when F  = 1.2/year and fishing started at age 3, R₀ was estimated to be 1.0 and the population was considered to be in equilibrium. For age-specific fishing mortality, when fishing started at age 3, R₀ was estimated to be 0.96/year, G being 6.18 years, and the population decreased 0.7% per year. The big eye population had a strong resilience as long as F  < = 1.3/year started at an age that was older than the age at maturity (i.e. 3 years old) but would decline when intensive fishing ( F  > = 1.2/year) started at age 2 or younger. Sensitivity analysis indicated that the mortality of age 0 is the most sensitive parameter in demographic analysis.     

Growth model for the endangered cyprinid fish Tribolodon nakamurai based on otolith analyses

A growth model for the endangered cyprinid fish Tribolodon nakamurai was derived following otolith analyses of 16 wild and 53 reared specimens. The asteriscus was the most appropriate to measure size among three otolith elements, and its height OH  mm was used as size index of otolith. Standard length L  cm was best back-calculated using the Gompertz model, L  = 70.0·exp[–exp{−0.553 (OH   –  2.73)}]. Translucent zones on the lapilli, analyzed from 5-year-old-reared fish, were regarded as winter slow-growing zones. The ages of 10 wild specimens of 37.0–48.1 cm standard length were calculated as 7–10 years by counting the translucent zones on the lapilli. Age t was best back-calculated using the allometry model, t  = 1.33· OH ^1.37. The growth trajectory of T.   nakamurai followed a slender S curve, three typical growth models, von Bertalanffy, Logistic and Gompertz, and Richards' model, which is a general formula of the above three, being fitted using the maximum likelihood method. The Gompertz model, L_t  = 60.2·exp[–exp{−0.258( t  − 4.68)}], was found by Akaike's information criterion (AIC) to be the statistically most acceptable growth model.     

Culture-based fisheries in non-perennial reservoirs of Sri Lanka: influence of reservoir morphometry and stocking density on yield

Abstract  Culture-based fish yield in non-perennial reservoirs of Sri Lanka was related to reservoir morphometry and stocking density. The reservoirs were stocked mainly with fingerlings of one Chinese and three Indian major carp species, common carp, Cyprinus carpio L., and the genetically improved farmed tilapia strain of Nile tilapia, Oreochromis niloticus (L.), at four pre-determined species combinations and a range of stocking densities [ SD (fingerlings ha⁻¹)]. Twenty-three reservoirs were harvested successfully at the end of the culture period of 2002–2003. Basic limnological and morphometric parameters, including shoreline development ( D _L ) and shoreline area ratio ( R _LA ), were estimated for each of the 23 reservoirs. Bray–Curtis similarity and non-metric multidimensional scaling using mean values of limnological data revealed that reservoirs could be ordinated into two major clusters, one with intact sample distribution due to similar trophic characteristics and the other with scattered sample distribution. Reservoirs in the cluster with similar trophic characteristics showed significant correlation ( P  < 0.05) between R _LA and total fish yield ( Y ). A multiple regression equation, Y  = −693 + 4810  R _LA  + 0.484 SD , was generated to estimate fish harvest in relation to SD .     

Temperature-dependent index of mitotic interval τ0 in greenling Hexagrammos otakii

ABSTRACT:   The aim of this study was to establish effective procedures for chromosome manipulation in greenling Hexagrammos otakii Jordan et Starks, which has enormous aquacultural potential. To accomplish this, temperature-dependent measurements of the mitotic intervals (τ₀) were carried out. The τ₀ in this fish was determined by averaging the duration of the first and third embryonic divisions at temperatures ranging 5–25°C. At higher temperatures, eggs developed faster and underwent more identical development. For greenling, τ₀ were 341.1 ± 3.60 min at 5°C, 275.5 ± 4.53 min at 10°C, 189.7 ± 6.93 min at 15°C, 99.2 ± 8.27 min at 20°C and 34.2 ± 8.74 min at 25°C. There were strong, negative correlations between the τ₀ and water temperatures at all temperatures studied ( Y  = −79.3 X  + 425.3, R ² = 0.9968, where Y is the mitotic interval and X is the temperature).     

Perish legally and ecologically: the ineffectiveness of the minimum landing sizes in the Mediterranean Sea

Abstract  Minimum landing size (MLS) is one technical measure used to manage fisheries with the aim of allowing enough juveniles to survive and spawn. In this study the practical and ecological efficiency of the MLSs set by European Union (Regulation 1967/2006) and Greek legislation for 13 fish species caught with five gears in the Ionian Sea was tested using length measurements from 22 382 individuals. The percentage of individuals with lengths smaller than MLS was estimated. In addition, MLSs were compared against length at 50% maturity ( L ₅₀) and the percentages of individuals caught per species and gear with lengths smaller than the L ₅₀ were also estimated. The mean percentage of individuals caught with lengths smaller than MLS ranged from 5.9% for longliners to 42.6% for beach-seiners, showing the practical inefficiency of this measure. In addition, all MLS were smaller than the corresponding L ₅₀ and L ₅₀ − SE values and across species the mean percentage of the immature individuals caught was very high, ranging from 55% for longliners to 92% for beach-seiners, indicating that the vast majority of the individuals caught did not have the chance to spawn even once. Thus, the existing MLSs are ecologically inefficient for sustainable management.     

Evaluation of genetic diversity of eight grouper species <Emphasis Type="Italic">Epinephelus</Emphasis> spp. based on microsatellite variations

ABSTRACT:   Genetic diversity among eight species of grouper, Epinephelus bleekeri , E. coioides , E. malabaricus , E. ongus , E. akaara , E. maculatus , E. merra and E. fuscoguttatus , was studied using six microsatellite loci, Em-01 *, Em-03 *, Em-07 *, Em-08 *, Em-10 *, and CA-07 *, with the aim of exploring the feasibility of using microsatellite data for species identification. The results showed high levels of genetic differentiation among species ( F _ST  = 0.4403 and R _ST  = 0.4954). Species identification based on fixed allelic differences was possible between E. coioides , E. ongus , and E. fuscoguttatus at Em-01 * and between E. fuscoguttatus and E. ongus at Em-08 *. Private alleles were found in all species, except for E. ongus . Pairwise F _ST ranged 0.238–0.578 ( P  < 0.008 Bonferroni correction), and Nei's genetic distance ranged 0.433–2.710. Size homoplasy was observed at Em-03 * 157 allele, which was characterized by a T–C transition at the 119th nucleotide site of PCR products. The genetic assignment test unambiguously assigned each individual to the correct species. Thus, this test can be used for species identification of unknown individuals when the multilocus genotypes of the six microsatellite loci are available. The phylogenetic (neighbor-joining) tree, which was constructed based on the genetic distance matrix, separated the eight grouper species into two main groups.