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.

Length-weight relationships of bivalves from coastal waters of Korea

Parameters a and b of the length (L)-weight (W) relationship W = a · Lb are presented for 17 commercial bivalve species collected from the southwest coastal waters of Korea. Estimates of b varied between 2.44 (Atrina pinnata japonica) and 3.31 (Scaphara broughtonii) with a mean of 2.891 (± 0.212). A total of 2 107 specimens were analyzed for this study. The length-weight relationship was isometric in most of the species.

An analysis of the multigear, multispecies fishery in the Kenyan waters of Lake Victoria

Catch rates for both Nile perch (Lates niloticus) and dagaa (Rastrineobola argentea) from Kenyan waters of Lake Victoria have steadily increased through the 1980s, even though the fishing effort also increased during the same period. However, analysis of catch and effort data within and outside the Nyanza Gulf suggests an increase in catch rates due to a shift in effort from the inshore Gulf region to higher catch rates in the offshore region, rather than an increase in abundance. Analysis of catch rates by gear type both in and outside the Nyanza Gulf show that 1991 catch rates are lower than 1989 levels by 60-80% in some instances. Since the fishing power of these gears has increased during this period, it is likely that fish abundance declined more than catch rates. A dynamic population model is used to stimulate Nile perch dynamics. It indicates that a decline in catches should be anticipated.

Preliminary observation on culture of Penaeus monodon in low-saline waters

The feasibility of semi-intensive culture of Penaeus monodon in low saline environment was investigated by comparing the growth and production in low (0.16-6.52 ppt) and high (4.60-19.42 ppt) saline areas at two stocking densities (10.5 and 16 individuals/m super(2)). After 135 days of culture, yield of shrimp in low and high stocking densities was 1563.37 kg/ha and 2274 kg/ha, respectively, in low saline ponds, and 1173.00 and 1974.00 kg/ha, respectively in high saline ponds. Food conversion ratio (FCR, 1.31-1.58) and specific growth rate (SGR 21.04-21.19%) were higher in low saline ponds as compared to high saline ponds (FCR, 1.35-1.68; SGR, 19.22-19.88%). Growth of shrimp was satisfactory in low saline ponds even when salinity decreased after 60 days of culture to almost freshwater level (0.16 ppt) indicating the variability of semi-intensive culture of P. monodon in low saline environment.

A review of length-weight relationships of fishes from Greek marine waters

This paper presents 649 length-weight relationships gathered from literature pertaining to 83 fish species, belonging to 34 families, throughout Greek marine waters. The value of the slope b ranged from 1.667 for Cepola macrophthalma to 3.707 for Mullus barbatus. The mean value of b was 2.989 (SD=0.339) and did not differ significantly from 3(t-test, p<0.05). The median value of b was 3.058 and 50% of the b values ranged between 2.900 and 3.186.

Biological parameters, body length-weight and length-height relationships for various species in Greek waters

Biological/fisheries parameters (L sub(oo) M, F) are presented for four fish species (Gadiculus argenteus; Gaidropsarus mediterraneous; Symphurus ligulatus; Lepidorhombus boscii) as well as body length-weight and length-height relationships for 11 and 12 fish species, respectively, estimated from trawl samples collected using three different cod-ends (stretched mesh size: 14 mm and 20 mm diamond-shaped and 20 mm square-shaped) during 1993-1994, in the western Aegean and North Euboikos Gulf, Greece. The fisheries paramaters, estimated from length-frequency using the ELEFAN approach and software, are discussed in the light of recent information on the selectivity of the presently used trawl cod-end (14 mm diamond shaped)

Estimating input demand and output supply elasticities in gillnet and seine fishing in Guimaras Strait and adjacent waters

This contribution is a summary of the results of the study conducted by the University of the Philippines in the Visayas team from November 1990 to June 1991. The purpose of this research is to estimate demand and output supply elasticities in gillnet and seine fishing in Guimaras Strait (Philippines) and adjacent waters.

Tilapia broodstock development for saline waters in the Philippines

Four Oreochromis species were used in the study. Progenies from the 27 cross combinations (5 pure breds and 22 crossbreds) were evaluated in 10 environments with different salinity levels and agro-climatic conditions using communal rearing concept. Among the different cross combinations reared across environments, O. aureus x O. spilurus gave the highest body weight and O. mossambicus x O. spilurus, the highest survival rate. Positive percent mean heterosis were observed in the crosses between O. mossambicus x O. niloticus, FAC selected line and O. aureus x O. spilurus.

Growth parameters of marine fishes in Cuban waters

A total of 73 sets of growth parameters for 34 species belonging to 12 families of marine fish caught in Cuban waters are presented. These parameters are compiled from existing studies (58 sets) or derived from data obtained in the original literature (15 sets).

Life history characteristics for silvergray rockfish (Sebastes brevispinis) in British Columbia waters and the implications for stock assessment and management

We summarize the life history characteristics of silvergray rockfish (Sebastes brevispinis) based on commercial fishery data and biological samples from British Columbia waters. Silvergray rockfish occupy bottom depths of 100−300 m near the edge of the continental shelf. Within that range, they appear to make a seasonal movement from 100−200 m in late summer to 180−280 m in late winter. Maximum observed age in the data set was 81 and 82 years for females and males, respectively. Maximum length and round weight was 73 cm and 5032 g for females and 70 cm and 3430 g for males. The peak period of mating lasted from December to February and parturition was concentrated from May to July. Both sexes are 50% mature by 9 or 10 years and 90% are mature by age 16 for females and age 13 years for males. Fecundity was estimated from one sample of 132 females and ranged from 181,000 to 1,917,000 oocytes and there was no evidence of batch spawning. Infection by the copepod parasite Sarcotaces arcticus appears to be associated with lower fecundity. Sexual maturation appears to precede recruitment to the trawl fishery; thus spawning stock biomass per recruit analysis (SSB/R) indicates that a F50% harvest target would correspond to an F of 0.072, 20% greater than M (0.06). Fishery samples may bias estimates of age at maturity but a published meta-data analysis, in conjunction with fecundity data, independently supports an early age of maturity in relation to recruitment. Although delayed recruitment to the fishery may provide more resilience to exploitation, managers may wish to forego maximizing economic yield from this species. Silvergray rockfish are a relatively minor but unavoidable part of the multiple species trawl catch. Incorrectly “testing” the resilience of one species may cause it to be the weakest member of the specie

The Bay Scallop, Argopecten irradians, in Florida Coastal Waters

The bay scallop, Argopecten irradians, supported a small commercial fishery in Florida from the late 1920’s through the 1940’s; peak landings were in 1946 (214,366 lbs of meats), but it currently supports one of the most popular and family-oriented fisheries along the west coast of Florida. The primary habitat of the short-lived (18 months) bay scallop is seagrass beds. Peak spawning occurs in the fall. Human population growth and coastal development that caused habitat changes and reduced water quality probably are the main causes of a large decline in the scallop’s abundance. Bay scallop restoration efforts in bays where they have become scarce have centered on releasing pediveligers and juveniles into grass beds and holding scallops in cages where they would

Seasonal Occurrence of the White Shark, Carcharodon carcharias, in Waters off the Florida West Coast, with Notes on its Life History

The white shark, Carcharodon carcharias, is considered rare in the Gulf of Mexico; however, recent longline captures coupled with historical landings information suggest that the species occurs seasonally (winter-spring) within this region. We examined a total of seven adult and juvenile white sharks (185-472 em total length) captured in waters off the west coast of Florida. Commercial longline fisheries were monitored for white sharks during all months (1981-94), but this species was captured only from January to April. All white sharks were captured in continental shelf waters from 37 to 222 km off the west coast of Florida when sea surface temperatures ranged from 18.7° to 21.6°C. Depths at capture locations ranged from 20 to 164 m. Fishing gear typically used in Gulf of Mexico offshore fisheries may not be effective at capturing this species, and the apparent rarity of white sharks in this area may be, in part, a function of gear bias.

The Status of Loggerhead, Caretta caretta; Kemp's Ridley, Lepidochelys kempi; and Green, Chelonia mydas, Sea Turtles in U.S. Waters: A Reconsideration

Assessing the status of widely distributed marine species can prove difficult because virtually every sampling technique has assumptions, limitations, and biases that affect the results of the study. These biases often are overlooked when the biological and nonbiological implications of the results are discussed. In a recent review, Thompson (1988) used mostly unpublished population census data derived from studies conducted by the National Marine Fisheries Service (NMFS) to draw conclusions about the status of Kemp's ridley, Lepidochelys kempi; Atlantic coast green turtles, Chelonia mydas; and the loggerhead sea turtle, Caretta caretta.

Feeding Ecology of the Franciscana (Pontoporia blainvillei) In Marine And Estuarine Waters Of Argentina

Stomach contents of 110 franciscanas (Pontoporia blainvillei), from northern Argentina were analysed in order to improve our knowledge about the feeding habits of this species and to better characterise the lactation period. The samples included calves, juveniles and adults of both sexes. Evidence of predation by franciscanas is seen at a very young age (2.5-3 months), with a transition diet composed by both milk and solid food, mainly represented by crustaceans. Weaning seems to begin by April, when franciscanas are about 6-7 months old. Franciscanas inhabiting two different habitats were analysed in this study: a brackish water estuary and an adjacent marine coastal system. The diet of Pontoporia blainvillei in northern Argentina was composed by a total of 26 prey species: 20 teleosts, 4 crustaceans and 2 cephalopods. Based on the Index of Relative Importance (IRI) the main prey species were Cynoscion guatucupa, Micropogonias furnieri, Loligo sanpaulensis and Urophycis brasiliensis. Estuarine franciscanas preyed mainly on Micropogonias furnieri (dominant species), Cynoscion guatucupa, Odonthestes argentinensis and Macrodon ancylodon, while dolphins from marine areas preyed mainly on Cynoscion guatucupa (dominant species), Loligo sanpaulensis and Urophycis brasiliensis. Our results confirm that franciscanas prey mainly on juvenile fish (< 8cm) and small loliginid squids, in close agreement with previous results obtained in southern Brazil and Uruguay. Qualitative and quantitative differences observed in the diet of dolphins from each habitat emphasise the need to discriminate between samples from different habitats and environmental parameters. SPANISH: Se analizaron 110 contenidos estomacales de franciscanas (Pontoporia blainvillei) provenientes de la costa norte de Argentina, para extender en conocimiento sobre su dieta y caracterizar la lactancia. Las muestras incluyeron cachorros, juveniles y adultos de ambos sexos. Las primeras etapas de predación se inician a muy temprana edad (2,5-3 meses), presentando una dieta de transición compuesta tanto por leche como por presas sólidas, principalmente crustáceos; el destete se iniciaría a partir de abril, a una edad estimada entre 6 y 7 meses. Las franciscanas estudiadas provienen de dos habitats diferentes: un área estuarial de baja salinidad y la region marina adyacente. La dieta de Pontoporia blainvillei de Argentina estuvo compuesta por un total de 26 especies: 20 teleósteos, 4 crustáceos y 2 cefalópodos. Basados en el Indice de Importancia Relativa (IIR), las presas más importantes fueron Cynoscion guatucupa, Micropogonias furnieri, Loligo sanpaulensis y Urophycis brasiliensis. Las franciscanas provenientes del área estuarial predaron principalmente sobre Micropogonias furnieri (especie dominante), Cynoscion guatucupa, Odonthestes argentinensis y Macrodon ancylodon, mientras que los delfines marinos predaron sobre Cynoscion guatucupa (especie dominante), Loligo sanpaulensis y Urophycis brasiliensis. Nuestros resultados confirman que la franciscana preda sobre peces juveniles (< 8cm) y pequeños calamares Loliginidae, coincidiendo con resultados previos obtenidos en el sur del Brasil y Uruguay. Las diferencias cualitativas y cuantitativas observadas en la dieta de cada uno de las áreas analizadas, nos sugieren que los futuros estudios sobre ecología trófica de la franciscana deberían discriminarse de acuerdo al origen de los ejemplares y a la tipificación del ambiente.