Age,growth and age at sexual maturity of fan ray <Emphasis Type="Italic">Platyrhina sinensis</Emphasis> (Batoidea: Platyrhinidae) in Ariake Bay,Japan

Abstract:   Age, growth and sexual maturity of the fan ray Platyrhina sinensis in Ariake Bay, Japan were determined from specimens collected from May 2002 to September 2006. Age determination was conducted by vertebral centrum analysis using soft X-radiography. Annual band pair deposition was determined by marginal increment and edge analyses. The von Bertalanffy growth model best described the overall pattern of growth for both males and females (males L _∝  = 455.2, k  = 0.56, t ₀ = −1.09; females L _∝  = 555.8, k  = 0.28, t ₀ = −1.77; 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). Parameter estimates suggest that females attain a larger asymptotic total length and grow more slowly than males. The observed maximum ages were 5 years for males and 12 years for females. Age at 50% sexual maturity was 2.1 years for males and 2.9 years for females. The results indicate that this species is relatively fast-growing, short-lived and early maturing compared with many batoid species.     

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.     

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.     

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.     

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.     

Proximate composition of some north-eastern Pacific forage fish species

To understand the relative dietary value of forage fish as prey in the Bering Sea and Gulf of Alaska, whole organisms of 13 species were analysed for proximate composition (protein, oil, ash and moisture content). Eulachon ( Thaleichthys pacificus ) were high in oil (total lipid) (16.8% to 21.4%) and low in moisture (64.6% to 70.8%). Oil in capelin ( Mallotus villosus ) ranged from 2.1% to 14.0%. Juveniles of walleye pollock ( Theragra chalcogramma ), Atka mackerel ( Pleurogrammus monopterygius ), Pacific herring ( Clupea pallasii ), and prowfish ( Zaprora silenus ) had low oil contents (< 1.8%) and high moisture contents (> 80.3%). Rankings of median proximate values illustrate the similarities. Surf smelt ( Hypomesus pretiosus ), rainbow smelt ( Osmerus mordax ), pricklebacks ( Lumpenus spp.), Atka mackerel, Pacific sand lance ( Ammodytes hexapterus ) and Pacific sandfish ( Trichodon trichodon ) ranked high in median protein content (> 15.4%). Median ash content for all species ranged from 0.6% to 3.3%. Total wet mass caloric content (kcal g^–1) was calculated for the four main species and a linear model was developed for caloric content as a function of moisture. The linear models (caloric content = b₀ + b₁ × moisture) were Pacific sand lance and Pacific sandfish (b₀ = 7.82, b₁ = – 0.09); eulachon (b₀ = 7.97, b₁ = – 0.08); and capelin (b₀ = 9.70, b₁ = – 0.11).     

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 .     

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.     

Characterization of 38 kDa and 42 kDa chitinase isozymes from the liver of Japanese common squid Todarodes pacificus

ABSTRACT: Characterization was investigated on the 38 kDa and 42 kDa chitinase (EC3.2.1.14) isozymes from the liver of Japanese common squid Todarodes pacificus . Optimum pH toward colloidal chitin was observed at pH 3.0 for the 38 kDa chitinase, and pH 3.0 and 9.0 for the 42 kDa chitinase. K _m and k _cat of the 38 kDa and 42 kDa chitinases toward a longer substrate, glycol chitin, were 0.071 mg/mL and 1.22/s, and 0.074 mg/mL and 0.196/s, respectively. Alternatively, strong substrate inhibition of both chitinases were observed toward a short substrate, N -acetylchitopentaose (GlcNAc₅). Both chitinases decomposed not only chitin but also chitosan (D. A. 95%). The cleavage pattern and reaction rate were investigated using N -acetylchitooligosaccharides (GlcNAc_n, n  = 2–6). Both chitinases hydrolyzed GlcNAc_n ( n  = 4,5, and 6). The release of GlcNAc was not observed. The speed of the reaction was observed to be in the following order: GlcNAc₄ > GlcNAc₅ > GlcNAc₆ for the 38 kDa chitinase, and GlcNAc₆ > GlcNAc₅ > GlcNAc₄ for the 42 kDa chitinase. Both the chitinases released p -nitrophenol from p -nitrophenyl GlcNAc_n ( n  = 2, 3, and 4). N-terminal amino acid sequences of the 38 kDa and 42 kDa chitinases were YLLSXYFTNWSQYRPGAGKYFPQNI and EYRKVXYYTNWSQYREVPAKFFPEN, respectively.     

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 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.     

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).     

A comparison of gastrically and surgically implanted telemetry transmitters in shovelnose sturgeon

Abstract  Transmitter retention and the effects gastrically and surgically implanted telemetry transmitters had on condition and mortality of shovelnose sturgeon, Scaphirhynchus platorhynchus (Rafinesque), >450-mm fork length were examined. Four, 35-day trials were conducted with approximately equal numbers of control fish, fish receiving dummy transmitters gastrically and fish receiving dummy transmitters surgically. Four sturgeon expelled gastrically implanted transmitters during the observation period. Two mortalities occurred among fish receiving gastrically implanted transmitters during the study period and one mortality was recorded for control fish. No mortalities were recorded for fish receiving surgically implanted transmitters. Condition change (Δ K _n ) was significantly different between fish receiving surgical implantation (mean Δ K _n  ± SE; −5.17 ± 0.94), fish receiving gastric implantation (−2.98 ± 0.72) and control fish (−0.65 ± 1.09). Surgical transmitter implantation is recommended for telemetry studies on shovelnose sturgeon because of increased transmitter expulsion and occurrence of mortality in fish receiving gastric implantation.     

Foraging specialisms, prey size and life-history patterns: a test of predictions using sympatric polymorphic Arctic charr (Salvelinus alpinus)

Abstract –  We use arguments based on optimal foraging theory to predict body size constraints and the consequences of these on a range of life-history traits in three trophic specialist morphs of Arctic charr, Salvelinus alpinus , living in sympatry in Loch Rannoch, Scotland. As predicted, foraging specialists feeding on small prey items with a narrow size range showed evidence of deterministic growth; the ultimate body size of macrobenthos feeders being larger ( L _∞ = 238 mm) than that of planktivores ( L _∞ = 216 mm). In contrast, the piscivorous morph showed no evidence of reaching a maximal body size.
The two size-constrained morphs (benthivores and planktivores) matured earlier and died younger (living for up to 11 and 7 years, respectively, in this study) than did the piscivorous charr which showed continuous growth up to at least 17 years.
The pattern of annual reproductive investment in maturing individuals was complex. Planktivores invested in larger eggs than the other two forms, but benthivores produced a greater number of eggs than planktivores, which in turn produced more than piscivores. Planktivorous males had a greater investment in mean testis weight than the other two forms.
Lifetime reproductive output was the greatest in the benthivorous charr, intermediate in planktivorous and the lowest in the piscivorous charr when measured either as fecundity or as gonadal weight. We conclude that constraints imposed upon foraging specialists by foraging efficiency is a significant driver of body size and ultimately reproductive investment in gape-limited foraging salmonids.     

Body shape variation in two species of darters (Etheostoma,Percidae) and its relation to the environment

Environmental variation can shape phenotypic variation in organisms, but most evidence for trait differentiation comes from analyses of dichotomous habitat types that differ in only one or few key environmental factors. In reality, environmental variation is often more subtle, gradual and multifarious. Here, we investigated geographic variation in body shape of two darter species (Etheostoma spectabile and Etheostoma flabellare; Percidae) that occur along river gradients. This study addressed three specific questions: Is there intraspecific geographic variation in the two species across different sites in the Ozark Highlands of Oklahoma (USA)? Is phenotypic variation across sites correlated with abiotic environmental conditions? Do the two species share site‐specific (i.e. convergent) phenotypic variation in areas where they occur together? Our results indicated significant body shape variation in both species. Population differences in body shape were particularly correlated with variation in substrate composition. The combined analysis of both species indicated a small but significant effect of convergence on body shape wherever they are sympatric; shared variation, however, was not related to any environmental variables included in the analysis. While it remains unclear whether phenotypic variation in these species is due to heritable differentiation or environmentally induced plasticity, our results indicate that even subtle and gradual environmental variation can induce substantial variation in phenotypes on a relatively small spatial scale.     

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.     

Effect of body size, photophase, feeding and emersion on the oxygen consumption of the east coast rock lobster Panulirus homarus rubellus

An understanding of the effect of key intrinsic and extrinsic factors on the oxygen consumption of Panulirus homarus rubellus is imperative for the development of optimized transport, holding and growout protocols. This study investigated the effect of body weight, photophase, feeding and emersion on the oxygen consumption rate of P. h. rubellus . Body weight was positively correlated to both standard and active oxygen consumption (mg O₂ h⁻¹) while body weight was negatively correlated to mass-specific standard oxygen uptake (mg O₂ g⁻¹ h⁻¹). Diurnal rhythm exhibited a strong effect on the lobsters' oxygen consumption, with average nighttime values 67% greater than those recorded during the day. This was related to activity driven by intrinsic nocturnal foraging behaviour. Feeding resulted in a classic specific dynamic action response, with postprandial oxygen consumption increasing to a peak before decreasing gradually to preprandial levels. Emersion caused a significant increase in oxygen consumption following re-immersion. Lobsters rapidly recovered to pre-emersion levels after 4 h following a 1-h emersion and after 13.3 h following an emersion period of 6 h. The implications of these results with regard to the holding/culture system and protocol design are discussed.     

An experimental investigation on aspects of infectious salmon anaemia virus (ISAV) infection dynamics in seawater Atlantic salmon, Salmo salar L.

This study investigated infection dynamics of infectious salmon anaemia virus (ISAV) by conducting two experiments to examine minimum infective dose and viral shedding of ISAV. In terms of minimum infective dose, the high variability between replicate tanks and the relatively slow spread of infection through the population at 1 × 10¹ TCID₅₀ mL⁻¹ indicated this dose is approaching the minimum infective dose for ISAV in seawater salmon populations. A novel qPCR assay incorporating an influenza virus control standard with each seawater sample was developed that enabled the quantity of ISAV shed from infected populations to be estimated in values equivalent to viral titres. Viral shedding was first detected at 7 days post-challenge (5.8 × 10⁻² TCID₅₀ mL⁻¹ kg⁻¹) and rose to levels above the minimum infective dose (4.2 × 10¹ TCID₅₀ mL⁻¹ kg⁻¹) on day 11 post-challenge, 2 days before mortalities in ISAV inoculated fish started. These results clearly demonstrate that a large viral shedding event occurs before death. Viral titres peaked at 7.0 × 10¹ TCID₅₀ mL⁻¹ kg⁻¹ 15 days post-infection. These data provide important information relevant to the management of ISA.