Population parameters of small pelagic fishes caught off Tawi-Tawi, Philippines

Growth and mortality parameters, exploitation rates and annual recruitment patterns were estimated from monthly length-frequency samples for Sardinella longiceps, S. fimbriata, S. Albella, Decapterus macrosoma, Dipterygonatus balteatus, Rastrelliger faughni and Encrasicolina heteroloba. These results provide the first sets of stock parameter estimates for these species off Tawi-Tawi, Philippines. The growth parameters derived were found comparable with previous estimates available for the same species from other localities. Recruitment was noted to be year-round and bimodal. Estimates of fishing mortality and exploitation rate were found to be presently above appropriate levels.

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.

Zooplankton population periodicity in a tropical pond

Results of a study on periodicity of zooplankton in small tropical pond are presented. This study was conducted in order to facilitate the design of a pond-based zooplankton production system.

Population parameters of 'corvina' (Plagioscion squamosissimus) in the Barra Bonita Reservoir, Brazil

Estimates for the growth parameters (L sub( infinity ) and K) mortality coefficients (Z,M and F) and exploitation rate (E) for the sciaenid Plagioscion squamosissimus are presented. The following results were obtained: 1) for male: L sub( arrow right )=44.2 cm, K=0.30 yr super(1), Z=0.82 yr super(1), M=0.66 yr super(1), F=0.16 yr super(1), and E=0.20; and 2) for females: L sub( arrow right )=68.4, K=0.22 yr super(1), Z=0.91 yr super(1), M=0.47 yr super(1), F=0.44 yr super(1) and E=0.49. Females are more heavily fished than males. Artisanal fishing carried out with gillnets, is mainly directed toward the young section of the population and individuals reproducing for the first time.

Population parameters of Pennahia anea and Nibea maculata in the Palk Bay/Gulf of Mannar area, India

The population parameters of the two most abundant sciaenids comprising the trawl catch in the Palk Bay/Gulf of Mannar area are presented. The following parameters were estimated: 233 mm (L sub( infinity )), 1.26 yr super(1) (K), -0.08 yr (t sub(0)), 4.24 yr super(1) (Z) and 2.24 yr super(1)(M) for Pennahia anear, 284 mm (L sub( infinity )), 1.08 yr super(1) (K), -0.05 yr (t sub(0)), 4.41 yr super(1) (Z) and 1.92 yr super(1) for Nibea maculata. Length at first capture was 97 mm for P. anea and 124 mm for N. maculata. These lengths were noted to be less than the corresponding length at first maturity for both species. The exploitation rates (E) derived indicate that the two species are heavily fished, which may account for the decline in sciaenid catches from 1988 to 1992.

Population control in farmed tilapias

Under the majority of culture practices, the reduction or elimination of reproduction in culture ponds results in significantly improved yields of marketable fish. An examination is made of existing methods for the control of reproduction in tilapias (Oreochromis spp.). The generation of all-male tilapia by hormonal sex reversal and genetic manipulation is discussed in detail, indicating the various advantages and disadvantages of both techniques.

Population dynamics and exploitation of Metapenaeus affinis in Kuwaiti waters

Length-frequency data of Metapenaeus affinis collected from the trawl catches of R/V Bahith in Kuwaiti waters from 1985 to 1989 were combined with estimates of monthly total catch by the commercial and small-scale fleets operating in Kuwait, and analyzed using the Compleat ELEFAN software package. A major recruitment pulse of M. affinis occurs in spring and a minor one in autumn. Optimum relative yield per recruit (Y'/R) is obtained with the length-at-first capture (L sub(c)) of 24.4 cm CL for females and < 17.6 m CL for males. Virtual population analysis results indicated that the biomasses have decreased during the last three-year period for which data were available.