Consumption to biomass (Q/B) ratio and estimates of Q/B-predictor parameters for Caribbean fishes

Estimates of the Q/B ratio and parameters of equations to 'predict' Q/B values for 116 fish stocks in the Gulf of Salamanca, Colombia are presented. A compilation of these estimates available for Caribbean Sea fishes (264 stocks) is also provided for comparison purposes. General trends in the value of Q/B resulting from differences in the equation and parameter values used are briefly discussed.

Exploring the use of neural networks for biomass forecasts in the Peruvian upwelling ecosystem

A pilot study was conducted to study the ability of an artificial neural network to predict the biomass of Peruvian anchoveta Engraulis ringens, given time series of earlier biomasses, and of environmental parameters (ocenographic data and predator abundances). Acceptable predictions of three months or more appear feasible after thorough scrutiny of the input data set.

Optimization study of the structural HACFRA composition (Self Compacting Concrete Steel Fiber Reinforced)

The interest of HACFRA (self compacting concrete reinforced with steel fibers), is the combination of the residual strength increase and cracking decrease compared to plain concrete by the introduction of steel fibers in the mass with the advantages of the self-compacting. The paper presents an analysis of the influence of different components of the HACRFA and provides their selection, refered to the granular skeleton and to different steel fiber types and amount, in order to obtain an optimization of its features and structural behavior.

Diet composition of fish species from the southern continental shelf of Colombia

The diet composition of 30 fish species belonging to 16 families from the Pacific Coast of Colombia is described. Benthic crustaceans (37.5%) and bony fishes (23.7%, chiefly demersal) were the most important food items for the fish species analyzed. Data on diet composition of the fish species are presented for the first time which can be a source of information for trophic modeling.

The evolution of body muscle composition of the African catfish (Clarias gariepinus) (Burchell 1822)

Changes in body muscle composition of Clarias gariepinus were studied in fish reared from 1.08 g to 383 g mean body weight in a 201-day culture period. Changes in the amount of protein content, dry matter and ash free dry matter in the muscle tissue can be described as a function of body weight. The percentage of protein content was observed to be higher in bigger fish. Fat content was low throughout the fingerling stage. Specific growth rate decreased significantly at 400 g mean body weight (P<0.05) while feed conversion rate increased. The conclusion, based on the culture conditions in this study, is that the optimal weight for harvesting C. gariepinus is 400 g.

VPA estimates of fishing mortality and exploited biomass from Sardinella aurita catch-at-length data in eastern Venezuela

In this study, length-frequency data on Spanish sardine (Sardinella aurita) from northeastern Venezuela were analyzed for the period 1967-1989. Average growth parameters for the von Bertalanffy equation were established as L sub( infinity )= 26.6 cm (TL) and K = 1.26 year super(-1). The number of recruits to the fishing area, estimated from length-structured Virtual Population Analysis, varied from <10 super(8) in the late 1960s to >10 super(9) at the end of the 1980s. Exploited biomass estimates for the same period varied from less than 20,000 t in the first year to more than 100,000 in 1989. Both recruitment and exploited biomass showed different seasonal patterns between 1976-1983 and 1984-1988. Despite some uncertainty regarding these estimates, it is considered that major population tendencies are adequately represented by this analysis

Nearshore fish resources and fisheries around Kigoma, eastern coast of Lake Tanganyika

The fish habitats along an inshore water stretch along the eastern/central coast of Lake Tanganyika are discussed and a quantitative analysis of the species composition, distribution and abundance of the littoral fishes within the area of study is presented. Seventy-one species of fish belonging to 48 genera and to 15 fish families were collected and identified during the study. The majority of species belonged to the Cichlidae family. Intensive beach seining for clupeids is suggested as one of the causes of low fish biomass in the area surveyed. The areas south of Kigoma appeared to contain more fish, with average catch rates of 11.7 kg/haul than those north of Kigoma where average catch rates of 7.6 kg/haul were recorded. Some suggestions for improved management of these resources are given.

Food consumption/biomass ratios of the pelagic fish community of Lake Malawi/Niassa

An empirical model relating food requirements to morphometric indices of metabolic rate was used to calculate consumption/biomass ratios (Q/B) for 16 species of fish that make the pelagic fish community in Lake Malawi/Niassa. The Q/B/year varied from 3.31 to 9.82, with the large catfish (Dinotopterus nyasensis) having the lowest and a small cyprinid (Engraulicypris sardella) having the highest Q/B ratio. Direct estimates of Q/B for four of the most abundant species, based on analysis of diel feeding patterns, ranged from 4.20 to 24.70; the extreme values in this range representing replicate studies on the same species, the predatory cichlid Rhamphochromis longiceps. Previous studies that indicated exceptionally low Q/B ratios (1.0) in pelagic cichlids from Lake Malawi are not supported by this more recent work.

Diet composition and daily ration estimates of selected trawl-caught fishes in San Miguel Bay, Philippines

The diet composition of fish caught in San Miguel Bay, Philippines, in April and May 1993 was studied. The diets of tiger-tooth croaker (Otolithes ruber), commerson's anchovy (Stolephorus commersonii); and the Indian anchovy (Stolephorus indicus) consisted mainly of zooplankton, primarily crustaceans. The stomach content of orangefin ponyfish (Leiognathus bindus) was found to consist mostly of detritus and unidentified materials. Daily rations estimated were: 1.90 g day super(1) for O. ruber of 17.3 g mean body weight (BW), 0.078 g day super(1) for S. commersonii) of 3.8 g mean BW, 0.062 g day super(1) for S. indicus of 3.9 g mean BW and 0.56 g day super(1) for L. bindus of 7.7 g mean BW.

Improving Shepherd's Length Composition Analysis (SLCA) method for growth parameter estimations

Shepherd's "weekly parametric" method for estimating the parameter L sub( infinity ) and K of the von Bertalanffy growth function from length-frequency data often fails to converge, and usually overestimates K. It is shown that this is due to overcounting of the frequencies associated with large, slow growing fish, and that both of these problems can be completely overcome by a simple change in the way the scoring function is formulated.

Biological reference points for managing kingfish, Scomberomorus commerson, in Oman

The 1987-1995 length composition of quarterly catches of Scomberomorus commerson (Lacepede 1800) was analyzed to determine various biological reference points for management purposes. These include: fishing mortality producing maximum yield-per-recruit in weight (F sub(max)), fishing mortality producing 50% relative mean mature biomass (F sub(50)), and fishing mortality producing recruits that would exactly replace their parent stock (F sub(rep)). F sub(max) provided misleading suggestions to increase fishing mortality on the stock which is currently at a low level. On the other hand, both F sub(50) and F sub(rep) provided acceptable results, suggesting reduction on the current fishing mortality by 17-40%.