Validated age and growth of the porbeagle shark (Lamna nasus) in the western North Atlantic Ocean

Growth parameters were estimated for porbeagle shark (Lamna nasus) in the northwest Atlantic Ocean on the basis of vertebral annuli. A total of 578 vertebrae was analyzed. Annuli were validated up to an age of 11 years by using vertebrae from recaptured oxytetracycline-injected and known-age sharks. Males and females grew at similar rates until the size of male sexual maturity, after which the relative growth of the males declined. The growth rate of the females declined in a similar manner at the onset of maturity. Growth curves were consistent with those derived from tag-recapture analyses (GROTAG) of 76 recaptured fish and those based on length-frequency methods with measurements from 13,589 individuals. Von Bertalanffy growth curve parameters (combined sexes) were L∞ = 289.4 cm fork length, K = 0.07 and t0 = –6.06. Maximum age, based on vertebral band pair counts, was 25 and 24 years for males and females, respectively. Longevity calculations, however, indicated a maximum age of 45 to 46 years in an unfished population.

Seasonal growth of King George whiting (Sillaginodes punctata) estimated from length-at-age samples of the legal-size harvest

Samples of 11,000 King George whiting (Sillaginodes punctata) from the South Australian commercial and recreational catch, supplemented by research samples, were aged from otoliths. Samples were analyzed from three coastal regions and by sex. Most sampling was undertaken at fish processing plants, from which only fish longer than the legal minimum length were obtained. A left-truncated normal distribution of lengths at monthly age was therefore employed as model likelihood. Mean length-at-monthly-age was described by a generalized von Bertalanffy formula with sinusoidal seasonality. Likelihood standard deviation was modeled to vary allometrically with mean length. A range of related formulas (with 6 to 8 parameters) for seasonal mean length at age were compared. In addition to likelihood ratio tests of relative fit, model selection criteria were a minimum occurrence of high uncertainties (>20% SE), of high correlations (>0.9, >0.95, and >0.99) and of parameter estimates at their biological limits, and we sought a model with a minimum number of parameters. A generalized von Bertalanffy formula with t0 fixed at 0 was chosen. The truncated likelihood alleviated the overestimation bias of mean length at age that would otherwise accrue from catch samples being restricted to legal sizes.

Age, growth, mortality, and distribution of pinfish (Lagodon rhomboides) in Tampa Bay and adjacent Gulf of Mexico waters

Life-history dynamics of pinfish (Lagodon rhomboides) were examined from data derived from random station surveys conducted in Tampa Bay and adjacent Gulf of Mexico waters during 1993–97. In addition, patterns in spatial distribution and abundance in Gulf of Mexico waters were investigated. Ages determined from whole otoliths ranged from 0 to 7 years, and von Bertalanffy growth models for males and females were not significantly different. Von Bertalanffy growth model parameters were L∞=219.9 mm SL, k =0.33/yr, and t0 =–1.10 years for all fish combined. High gonadosomatic indices during October–December indicated that some spawning may occur in Tampa Bay. Estimated lengths at 50% maturity were 132 mm SL for males and 131 mm SL for females. Total instantaneous mortality rates derived from the Chapman-Robson estimator ranged from 0.88 to 1.08/yr, and natural mortality was estimated to be 0.78/yr. In Gulf of Mexico waters, pinfish catch rates declined with increasing depth, and most pinfish were caught in <17 m of water. Length distributions showed that pinfish segregate by size with increasing depth.

Age and growth of the smooth dogfish (Mustelus canis) in the northwest Atlantic Ocean

The northwest Atlantic population of smooth dogfish (Mustelus canis) ranges from Cape Cod, Massachusetts, to South Carolina. Although M. canis is seasonally abundant in this region, very little is known about important aspects of its biology, such as growth and reproductive rates. In the early 1990s, commercial fishery landings of smooth dogfish dramatically increased on the east coast of the United States. This study investigated growth rates of the east coast M. canis population through analysis of growth patterns in vertebral centra. Marginal increment analysis, estimates of precision, and patterns in seasonal growth supported the use of vertebrae to age these sharks. Growth bands in vertebral samples were used to estimate ages for 894 smooth dogfish. Age-length data were used to determine von Bertalanffy growth parameters for this population: K = 0.292/yr, L∞ = 123.57 cm, and t0 = –1.94 years for females, and K = 0.440/yr, L∞ = 105.17 cm, and t0 = –1.52 years for males. Males matured at two or three years of age and females matured between four and seven years of age. The oldest age estimate for male and female samples was ten and sixteen years, respectively.

Age and growth of the swordfish (Xiphias gladius L.) in the waters around Taiwan determined from anal-fin rays

Age and growth of the swordfish (Xiphias gladius) in Taiwan waters was studied from counts of growth bands on cross sections of the second ray of the first anal fin. Data on lower jaw fork length and weight, and samples of the anal fin of male and female swordfish were collected from three offshore and coastal tuna longline fishing ports on a monthly basis between September 1997 and March 1999. In total, 685 anal fins were collected and 627 of them (293 males and 334 females) were aged successfully. The lower jaw fork lengths of the aged individuals ranged from 83.4 to 246.6 cm for the females and from 83.3 to 206 cm for the males. The radii of the fin rays and growth bands on the cross sections were measured under a dissecting microscope equipped with an image analysis system. Trends in the monthly marginal increment ratio indicated that growth bands formed once a year. Thus, the age of each fish was deter-mined from the number of visible growth bands. Two methods were used to estimate and compare the standard and the generalized von Bertalanffy growth parameters for both males and females. The nonlinear least square estimates of the generalized von Bertalanffy growth parameters in method II, in which a power function was used to describe the relationship between ray radius and LJFL, were recommended as most acceptable. There were significant differences in growth parameters between males and females. The growth parameters estimated for females were the following: asymptotic length (L∞) = 300.66 cm, growth coefficient (K) = 0.040/yr, age at zero length (t0) = –0.75 yr, and the fitted fourth parameter (m) = –0.785. The growth parameters estimated for males were the following: asymptotic length (L∞) = 213.05 cm, growth coefficient (K) = 0.086/yr, age at zero length (t0) = –0.626 yr, and the fitted fourth parameter (m) = –0.768.

Assessment of Saurida tumbil (Bloch) stock in the northwest continental shelf water of India

Based on the data collected from New Ferry Wharf, Sassoon Dock and exploratory survey of MFV Saraswati on the Northwest coast of India, the growth, mortality, population and stock parameters of Saurida tumbil is reported in the present communication. The Von Bertalanffy growth function (GF) parameters for growth on length were found to be L∞=49.8 cm, K=0.96/year, t0 = -.141 year. The length at recruitment (lr) is 80 mm. (tr=.167 year) while the length at first capture (lc) for the commercial trawl fishery is 100 mm (tc=0.25 year). The annual fishing mortality coefficient (F) for 1983-85 was 0.43, the natural mortality coefficient (M) was 1.33 and the exploitation ratio (E) was 0.25. The yield per recruit (Y/R) attained the maximum of 54.99 g at F=1.091 for E=0.45 for the present tc at 0.25 year. The annual total stock (P) and standing stock (P) in the exploitation portion at the inshore grounds to a depth of about 50 m were estimated to be 12,811 tons and 6,034 tons respectively. The average annual yield of 2,635 tons at the present F=0.439 (E=0.247) was less than the maximum sustainable yield (MSY) for 3,331 tons attainable from the inshore grounds at E=0.45.

Fishery and biology of white sardine, Escualosa thoracata (Valenciennes) at Versova, Bombay

Gill net fishery exclusively for the white sardine, Escualosa thoracata, which started in mid-eighties at Versova, is described. During 1987-88 to 1991-92 periods, the annual average landing of the species was 202.2 tons with year to year fluctuations. The peak fishing season was during April-May. The size range of the species in the gill net was 41-105 mm and the von Bertalanffy growth parameters, L. and K, estimated by the ELEFAN program were 110 mm and 1.8 per year. The length-weight relationship was W=0.000001508 L(super 3.3946) for the males and W=0.000002561 L(super 3.2706) for the females. The food consisted of copepods, cladocerans and crustacean larvae. The size at maturity for the females was 82 mm and spawning took place during October - February period. The sex-ratio showed equal proportion except during January, July and October when females dominated in the catch.

Population dynamics and stock assessment of the spider prawn, Nematopalaemon tenuipes Henderson along the Maharashtra coast

Nematopalaemon tenuipes is an important component of non-penaeid prawn resources of the northwest coast of India. During 1979-82 period, it contributed 29.9% to the non-penaeid prawn and 5.6% to the total fish landings of Maharashtra. The von Bertalanffy growth parameter L∞, K and t(sub)0 were 77.38 mm, 1.31 and -0.02 year for the males while for the females these parameters were respectively 87.23 mm, 1.30 and -0.01 year. The natural mortality coefficient (M) was 3.54 and 3.52 and the average total mortality coefficient (Z) during the period was 9.09 and 7.79 for the males and females respectively. With the exploitation rates of 0.61 and 0.55 for the males and females during the period, the total stock of the species was 26,270 tonnes and the standing stock was 3,418 tonnes. The maximum sustainable yield (MSY) of the species under the prevailing fishing conditions was 15,744 tonnes which is close to the average yield of 14,726 tonnes from the nets. Hence further increase in effort is not suggested.

Growth parameters of Lepturacanthus savala (Cuvier, 1829) from Mumbai waters

Lepturacanthus savala (Cuvier, 1829) constitutes a minor fishery contributing 23.3% to the total ribbonfish catch in Maharashtra. Based on the length data obtained from shrimp trawlers and the traditionally operated bag nets, age and growth of the species have been investigated from Mumbai waters. Growth was studied by various computer-based methods incorporated in FiSAT Programme. The growth parameters L∞ and K (on annual basis) by Gulland-Holt plot were 683.3 mm and 0.87, respectively. As the seasonal temperature variations in coastal waters of Mumbai are not pronounced, the seasonally oscillating growth patterns by ELEFAN and Appledoorn's method were not considered. Following the von Bertalanffy growth model, the fish attains 399.8, 567.2 and 637.4 mm at the end of 1, 2 and 3 years, respectively, and the lifespan of the fish is about 3.3 years.

A revision of growth parameters of some commercially exploited fishes from Mozambique

Data on age and growth of the following species were reviewed and von Bertalanffy's growth curves were fitted: Hilsa kelee, Decapterus russellii, D. macrosoma, Rastrelliger kanagurta, Pellona ditchela, Thryssa vitrirostris and Leiognathus equulus. For the five first species, microstructures in the otoliths were used for ageing. For most species growth curves based on size-frequency distributions are also presented. The reliability of the data presented is discussed.

Reproduction, age and growth of the round scad Decapterus macrosoma Blecker 1851, Carangidae from Mozambique

Reproduction, age and growth of Decapterus macrosoma Blecker, 1851 were studied. The data were collected in Sofala Bank from commercial bottom trawlers and surveys. A total of 5,500 individuals were examined during the period 1979-1982. The species is caught in the same areas as D. russellii, but appears in lower quantities. Two main spawning periods a year, one in December-February and another one in June-September were found. Ageing was determined by counting daily growth rings in the otoliths. The parameters of von Bertalanffy's growth equation were L infinity=26 cm and K=0,6/year. Males and females seem to grow at the same rate.

Preliminary estimation of growth in Cheimerius nufar (Sparidae) from southern Mozambique

On the basis of length-frequency data collected in 1987, by the hook-and-line fishery research program, preliminary estimates of the parameters of a seasonally oscillating version of the von Bertalanffy equation for Cheimerius nufar (Ehrenberg, 1830) were obtained, i.e., TL∞=70 cm and K=0.17 yearˉ¹. A discussion of these results is provided.

Growth of the buccaneer anchovy Encrasicholina punctifer off Mozambique, based on samples collected in research surveys

Growth of Encrasicholina punctifer (Engraulididae) is estimated, based on samples obtained during five surveys on Sofala Bank (central Mozambique). The estimated values of the von Bertalanffy growth function, TL∞=12 cm and K=2.0 yearˉ¹ are compared with results of growth studies elsewhere in the Indo-Pacific region, based mainly on the index Φ=log(sub)10 K+2*log(sub)10L∞ assumed to be constant within species. This comparison is rendered difficult by the uncertain taxonomical status of stolephorid anchovies.

Reproduction, age and growth of the kelee shad, Hilsa kelee (Cuvier, 1829) (pisces: fam. Clupeidae) with informations on its fishery in Maputo Bay, Mozambique

Age, growth and reproduction of H. kelee were studied, and a brief description of its fishery in Maputo Bay (Mozambique) is given. Most material was collected from gill net fisheries during 1977-1980, but some was taken from shrimp trawlers operating in the same area during 1980-1981. Main spawning takes place during October-January with a peak in December. There is also some evidence that spawning takes place during June-July. The size at first maturity was approximately equals 14-15 cm. Ageing was carried out using primary growth rings in the otoliths and length-frequency analysis of fish caught by shrimp trawlers. Von Bertalanffy's growth equation parameters were determined. Males and females grew in similar fashion. There are seasonal trends in the catch composition of the gill net fishery, showing high values during April to September and low during October to December.

Reproduction, age and growth of the Russell's scad, Decapterus russellii (Rüppel, 1828)(Carangidae) from Sofala Bank, Mozambique

Age, growth and reproduction of D. russellii were studied. Most of the material used was caught by the commercial fishing fleet, operating in the Sofala Bank (Mozambique) area. A total of 68,000 fish were examined during the period 1979-1981. There were 2 main spawning periods each year, one in February-March and another in August-September. The sex ratio was about 1:1. Ageing was carried out using primary growth rings in the otoliths and analysis of size-frequency distributions. The parameters of the von Bertalanffy's growth equation were determined. Males and females grew at the same rate.