Growth and seasonal recruitment of Octopus maya on Campeche Bank, Mexico

A study of growth and seasonal recruitment of the cephalopod Octopus maya on Campeche Bank, Mexico, was conducted, based on catch at size data sampled from 1983 to 1988. The parameters of a seasonally oscillating version of the von Bertalanffy growth function and total mortality estimates were obtained via the ELEFAN software. It was found that when recruitment occurs early in the year, the growth curve of the next year does not display seasonal oscillations, and conversely. Total mortality estimates ranged from Z = 2.6 to Z = 6.3/year.

Population parameters of Penaeus californiensis in the Gulf of Guayaquil, Ecuador

The growth, mortality, and recruitment pattern of Penaeus californiensis were investigated using tail length (TL)-frequency data obtained from the Gulf of Guayaquil shrimp population. Computer-based methods of tail-frequency analysis Compleat ELEFAN software were used. Results obtained gave relatively high growth and mortality estimates for both males and females. The recruitment pattern indicated two pulses annually, one significantly larger than the other.

Growth performance of Nigerian fish stocks

Parameters of the von Bertalanffy growth function are presented for 42 fish stocks belonging to 16 families, 22 genera and 27 species. The growth performance index, Phi '(= log K + 2logL sub( infinity )), was computed for each stock and was found to be highest in male Gymnarchus niloticus (Gymnarchidae) from Lake Chad and lowest in Chrysichthys auratus (Bagridae) from the Cross River. Mean Phi ' for major fish genera and families are also presented and was highest in brackishwater fishes, closely followed by freshwater and inshore marine water fishes.

Growth and mortality of dagaa (Rastrineobola argentea, Fam. Cyprinidae) in Lake Victoria

Growth and mortality parameters of the small Lake Victoria cyprinid Rastrineobola argentea were determined from length-frequency analysis, using the ELEFAN I and II programs. The results of two sampling programs, both performed during 1988, one in Uganda (mosquito seine) and the other in Tanzania (pelagic trawl), were highly corresponding, In comparison with previously published data on the growth of dagaa and some similar species, low values for L sub( infinity ) (65 mm standard length) and K (1 year super(-1)) were found. Total mortality (Z) amounted to 3.9-4.4 year super(-1). A single annual breeding peak was observed both in Uganda (October/November) and in Tanzania (February/March).

Estimates of growth and comparisons of growth rates determined from length- and age-based models for populations of purple wrasse (Notolabrus fucicola)

Growth of a temperate reefa-ssociated fish, the purple wrasse (Notolabrus fucicola), was examined from two sites on the east coast of Tasmania by using age- and length-based models. Models based on the von Bertalanffy growth function, in the standard and a reparameterized form, were constructed by using otolith-derived age estimates. Growth trajectories from tag-recaptures were used to construct length-based growth models derived from the GROTAG model, in turn a reparameterization of the Fabens model. Likelihood ratio tests (LRTs) determined the optimal parameterization of the GROTAG model, including estimators of individual growth variability, seasonal growth, measurement error, and outliers for each data set. Growth models and parameter estimates were compared by bootstrap confidence intervals, LRTs, and randomization tests and plots of bootstrap parameter estimates. The relative merit of these methods for comparing models and parameters was evaluated; LRTs combined with bootstrapping and randomization tests provided the most insight into the relationships between parameter estimates. Significant differences in growth of purple wrasse were found between sites in both length- and age-based models. A significant difference in the peak growth season was found between sites, and a large difference in growth rate between sexes was found at one site with the use of length-based models.

Age validation, growth modeling, and mortality estimates for striped trumpeter (Latris lineata) from southeastern Australia: making the most of patchy data

Age estimates for striped trumpeter (Latris lineata) from Tasmanian waters were produced by counting annuli on the transverse section of sagittal otoliths and were validated by comparison of growth with known-age individuals and modal progression of a strong recruitment pulse. Estimated ages ranged from one to 43 years; fast growth rates were observed for the first five years. Minimal sexual dimorphism was shown to exist between length, weight, and growth characteristics of striped trumpeter. Seasonal growth variability was strong in individuals up to at least age four, and growth rates peaked approximately one month after the observed peak in sea surface temperature. A modified two-phase von Bertalanffy growth function was fitted to the length-at-age data, and the transition between growth phases was linked to apparent changes in physiological and life history traits, including offshore movement as fish approach maturity. The two-phase curve was found to represent the mean length at age in the data better than the standard von Bertalanffy growth function. Total mortality was estimated by using catch curve analysis based on the standard and two-phase von Bertalanffy growth functions, and estimates of natural mortality were calculated by using two empirical models, one based on longevity and the other based on the parameters L∞ and k from both growth functions. The interactions between an inshore gillnet fishery targeting predominately juveniles and an offshore hook fishery targeting predominately adults highlight the need to use a precautionary approach when developing harvest strategies.

An environmentally based growth model that uses finite difference calculus with maximum likelihood method: its application to the brackish water bivalve Corbicula japonica in Lake Abashiri, Japan

We present a growth analysis model that combines large amounts of environmental data with limited amounts of biological data and apply it to Corbicula japonica. The model uses the maximum-likelihood method with the Akaike information criterion, which provides an objective criterion for model selection. An adequate distribution for describing a single cohort is selected from available probability density functions, which are expressed by location and scale parameters. Daily relative increase rates of the location parameter are expressed by a multivariate logistic function with environmental factors for each day and categorical variables indicating animal ages as independent variables. Daily relative increase rates of the scale parameter are expressed by an equation describing the relationship with the daily relative increase rate of the location parameter. Corbicula japonica grows to a modal shell length of 0.7 mm during the first year in Lake Abashiri. Compared with the attain-able maximum size of about 30 mm, the growth of juveniles is extremely slow because their growth is less susceptible to environmental factors until the second winter. The extremely slow growth in Lake Abashiri could be a geographical genetic variation within C. japonica.

Modeling red sea urchin (Strongylocentrotus franciscanus) growth using six growth functions

The growth of red sea urchins (Strongylocentrotus franciscanus) was modeled by using tag-recapture data from northern California. Red sea urchins (n=211) ranging in test diameter from 7 to 131 mm were examined for changes in size over one year. We used the function Jt+1 = Jt + f(Jt) to model growth, in which Jt is the jaw size (mm) at tagging, and Jt+1 is the jaw size one year later. The function f(Jt), represents one of six deterministic models: logistic dose response, Gaussian, Tanaka, Ricker, Richards, and von Bertalanffy with 3, 3, 3, 2, 3, and 2 minimization parameters, respectively. We found that three measures of goodness of fi t ranked the models similarly, in the order given. The results from these six models indicate that red sea urchins are slow growing animals (mean of 7.2 ±1.3 years to enter the fishery). We show that poor model selection or data from a limited range of urchin sizes (or both) produces erroneous growth parameter estimates and years-to-fishery estimates. Individual variation in growth dominated spatial variation at shallow and deep sites (F=0.246, n=199, P=0.62). We summarize the six models using a composite growth curve of jaw size, J, as a function of time, t: J = A(B – e–Ct) + Dt, in which each model is distinguished by the constants A, B, C, and D. We suggest that this composite model has the flexibility of the other six models and could be broadly applied. Given the robustness of our results regarding the number of years to enter the fishery, this information could be incorporated into future fishery management plans for red sea urchins in northern California.

Age and growth of blue rockfish (Sebastes mystinus) from central and northern California

Otoliths from blue rockfish (Sebastes mystinus), were aged by using a combination of surface and break-and-burn methods. The samples were collected between 1978 and 1998 off central and northern California. Annual growth increments in the otoliths were validated by using edge analysis for females up to age 23 and for males to age 25.The first annual growth increment was identified by comparing the diameter of the otolith from fish known to be one year old collected in May (when translucent zone formation was completed) to the mean diameter of the first translucent zone in the otoliths from older fish. Our estimated maxi-mum ages of 44 years for males and 41 years for females were much older than those reported in previous studies. Von Bertalanffy growth models were developed for each sex. Females grew faster and reached larger maximum length than males. The growth models were similar to those generated in other studies of this species in southern and central California. Fish from northern and central California had similar maximum sizes, maximum ages, and growth model parameters.

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.

Effect of brood source on the growth of rohu (Labeo rohita Ham.) fingerlings reared in glass tanks with formulated diets

A 60 day long feeding trial was conducted in an indoor static water system with rohu fingerlings (Labeo rohita Ham.) originating from wild brood, private and public hatcheries (denoted as A B and C respectively). They were fed on formulated diet having 34% crude protein level using indigenous ingredients. The effect of brood source on growth as well as their responses to formulated diet was observed. On the basis of the observed growth rate, food conversion ratio, protein efficiency ratio, apparent net protein utilization and apparent protein digestibility, fingerling source A showed significantly (p<0.05) higher growth, while the sources B and C produced no significantly different (p>0.05) in terms of these parameters. The results of the present study demonstrated that the fingerlings of wild source were of best quality in terms of growth and food utilization in comparison to those had the sources from hatcheries.

Effect of different rice brans on the growth of Thai silver barb (Puntius gonionotus Bleeker) in seasonal ponds

An experiment was conducted for a period of 110 days to study the effect of different rice brans on the growth of Thai silver barb (Puntius gonionotus, Bleeker) in rainfed seasonal ponds (30 m² each). Each of the ponds was stocked with 150 fish with the mean initial body weight of 2.03 ± 0.03 g. There were three treatments namely R1, R2 and R3 each having four replicates. Three types of rice bran namely coarse, auto (fine) and red were applied to the treatments R1, R2 and R3 respectively. Fish received different types of rice bran at a rate of 5% of body weight daily. The water quality parameters were found within the productive range. The results showed that treatment R1 produced significantly (p<0.05) highest growth and treatment R2 produced the lowest growth. The survival rates varied between 77 and 84% with treatment R3 producing the highest survival. However, the overall best production (1530 kg/ha) and economic return for the culture period was obtained in treatment R1 receiving coarse rice bran. The results of the present study demonstrated that the coarse rice bran resulted in better growth and production of P. gonionotus.

Effects of periphyton grown on bamboo substrates on growth and production of Indian major carp, rohu (Label rohita Ham.)

The effects of periphyton, grown on bamboo substrates, on growth and production of Indian major carp, rohu, Labeo rohita (Hamilton), were studied in 10 ponds during July to October '95 at the Bangladesh Agricultural University, Mymensingh. Five ponds were provided with bamboo substrates (treatment I) and the rests without bamboo substrates (treatment II). It was revealed that there had been no discernible difference in the water quality parameters between treatments. A large number of plankton (30 genera) showed periphytic nature and colonized on the bamboo substrates. The growth and production of fish was significantly (p<0.05) higher in the ponds with bamboo substrates as compared to the ponds without substrates. The net production of rohu in treatment I was about 1.7 times higher than that of treatment II. Fish production was as much as 1899 kg/ha over a culture period of 4 months in the periphyton-based production system.

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.