Ungewohnliche Gewichsabnahme von Dorsch im 2. Jahresquartal in Bornholm Becken (ICES-Gebeit 25) und der Arkonasee (ICES-Gebiet 24)

Cod captured by commercial fi shery in the Bornholm Basin in quarter 2 of 2001 were not suitable for the mechanical processing due to low condition and weight. The absolute mean weight of cod captured by the commercial fishery in the Arkona Sea and Bornholm Basin in the same quarter during the last fi ve years was studied to describe its development. The results of a GLM (Generalized Linear Model) analysis showed similar development of body weight in the Bornholm Basin and in the Arkona Sea between 2007 and 2011. The mean weight of cod in the Bornholm Basin increased from 2007 to 2008 in both areas followed by a relative stable weight until 2009 and a decrease until 2011. In the Arkona Sea the mean weight of cod 2009 has decreased in comparison to 2008, then have increased 2010 slightly and last have decreased in 2011. The analyses showed that the weight of cod is signifi cantly infl uenced by length, age and maturity of individuals.

Reproductive biology of male franciscanas (Pontoporia blainvillei) (Mammalia: Cetacea) from Rio Grande do Sul, southern Brazil

The reproductive biology of male franciscanas (Pontoporia blainvillei), based on 121 individuals collected in Rio Grande do Sul State, southern Brazil, was studied. Estimates on age, length, and weight at attainment of sexual maturity are presented. Data on the reproductive seasonality and on the relationship between some testicular characteristics and age, size, and maturity status are provided. Sexual maturity was assessed by histological examination of the testes. Seasonality was determined by changes in relative and total testis weight, and in seminiferous tubule diameters. Testis weight, testicular index of maturity, and seminiferous tubule diameters were reliable indicators of sexual maturity, whereas testis length, age, length, and weight of the dolphin were not. Sexual maturity was estimated to be attained at 3.6 years (CI 95% =2.7–4.5) with the DeMaster method and 3.0 years with the logistic equation. Length and weight at attainment of sexual maturity were 128.2 cm (CI 95%=125.3–131.1 cm) and 26.4 kg (CI 95% =24.7–28.1 kg), respectively. It could not be verified that there was any seasonal change in the testis weight and in the seminiferous tubule diameters in mature males. It is suggested that at least some mature males may remain reproductively active throughout the year. The extremely low relative testis weight indicates that sperm competition does not occur in the species. On the other hand, the absence of secondary sexual characteristics, the reversed sexual size dimorphism, and the small number of scars from intrassexual combats in males reinforce the hypothesis that male combats for female reproductive access may be rare for franciscana. It is hypothesized that P. blainvillei form temporary pairs (one male copulating with only one female) during the reproductive period.

Length-weight relationship and relative condition of Heterobranchus longifilis (Valenciennes) from Idodo River, Nigeria

Length-weight relationship parameters of Heterobranchus longifilis males, females and combined sexes are given. The samples were collected from Idodo River, with size ranging from 123 mm total length, L, to 936 mm L. The values obtained for the mean L by sex show that males were significantly (p<0.05) larger than females. The results show that the slope (b) is significantly (p<0.05) below 3.0 for the male, female and pooled sample. The species exhibit a negative allometric growth pattern. The relative condition of fish shows seasonal variation, with females generally being in better condition than the males.

Length-weight relationship and relative condition factor in Macrobrachium (Hellex)

The length-weight relationship was calculated for the freshwater prawn Macrobrachium idae. About 150 specimens of M. idae (males 50, females 50 and 50 juveniles) were utilised for this study. The length-weight relationship was assessed separately for males, females and indeterminants. The regression equation for males, females and indeterminants showed significant differences whereas it was insignificant for males and females. The variations in length-weight relation between sexes and indeterminants were compared and discussed. The relationship between total length with carapace length and total length with rostral length were also determined.

Length-weight relationships and relative conditions of two sciaenids Otolithes cuvieri Trewavas and Johnius elongatus Mohan from the Karachi coast

Estimates of length-weight relationship in Otolithes cuvieri justify separate equations for males (log W =-5.0100+3.1365 log L) and females (log W =-5.2000+3.1006 log L). Relative condition factor "Kn" was found to be 0.877-1.946 in males and 0.879-1.328 in females. High "Kn" values during March to September at 180-220 mm TL in either sexes are indicative of the maturation of gonads. Separate equations for length-weight relationship are also justified for males (log W = -5.1126 + 3.0690 log L) and females (log W = -5.6400 + 3.3070 log L) of Johnius elongatus . "Kn" values were found to be 0.924-1.894 for males and 0.894-1.087 for females. High "Kn" values during January-May and August-September at 130 mm TL onward are indicative of gonadal maturation.

Length-weight relationship and relative condition factor of pond-reared mahseer, Tor putitora(Ham.)

The study deals with the length-weight relationship and relative condition factor (Kn) of mahseer, Tor putitora reared for 150 days in ponds. The logarithmic form of equation for the relationship was found to be logW = -1.727+2.875logL or W=O.Ol875U·875 • The graphical presentation of the parabolic and logarithmic forms showed respectively the curvilinear and linear relationships between length and weight of the fish. The mean value (±sd) of relative condition factor was found to be 0.95±0.12. The exponential value 'b' was found to be 2.96 and the coefficient of correlation 'r' was 0.965, which showed strong and highly correlated relationships between length and weight of the fish.

Length-weight relationship and relative condition factor in Oreochromis mossambicus (Peters) of Bhima River

Oreochromis mossambicus (Peters), a common freshwater fish of Bhima river, has high economic value and considerable fishery importance. The length-weight relationship in the logarithmic way for this fish can be written as: Log W = - 4.50241627 + 2.884822741 log L. This is close to the cubic law indicating the isometric growth of the fish in its natural habitat. The correlation coefficient (r) was found to be 0.9865 which showed a good relationship between the two parameters. The mean relative condition factor (K sub(n)) was 1.00 suggesting the well-being of the fish.

Length-weight relationship and relative condition factor in Daysciaena albida (Cuv.) and Gerres filamentosus (Cuv.)

The length-weight relationship of Daysciaena albida and Gerres filamentosus were calculated separately for indeterminants, mature males and mature females. The logarithmic regression equation obtained for D. albida - males: log w = -1.5055 + 2.8618 log l; females: log w = -0.9260 + 2.4089 log l; indeterminants: log w = -l.7188 + 3.0616 log l. The regression co-efficients between males and females, males and in determinants and female and in determinants showed significant differences. In G. filamentosus the relationship can be expressed as males: log w = -1.3224 + 2.8740 log 1; females: log w = -1.2874 + 2.8381 log l; indeterminants: log w = -0.8167 + 2.2558 log l. The difference in regression co-efficients between male and female are insignificant at 5% level whereas significant differences were observed between males and indeterminants and females and indeterminants. The relative condition factor (Kn) was calculated for the above two species. In D. albida the reasons for the fluctuations of Kn values can be attributed to both spawning cycle as well as feeding intensity whereas in G. filamentosus it synchronies mainly with spawning cycle.

Seasonal foods, gonadal maturation, and length-weight relationships for nine fishes commonly captured by shrimp trawl on the Northwest Gulf of Mexico Continental Shelf

Recent emphasis on ecosystem approaches to fisheries management renews interest in, and the need for, trophic information about fish communities. A program was started in 1980 at the National Marine Fisheries Service Galveston Laboratory to develop a trophic database for continental shelf fishes. Collections were made during 1982-1983 that were processed but never published, yet the data remain valid today for historical purposes and for delimiting food web components within ecosystem assessments. I examined spring, summer, and fall foods in offshore populations of nine common species of trawl-susceptible fishes, with particular reference to predation on commercial penaeid shrimps (Farfantepenaeus and Litopenaeus). Diets were evaluated with the Index of Relative Importance (IRI) which combines the occurrence, number, and weight of each food item. Bank sea bass (Centropristis ocyurus) and bighead searobin (Prionotus tribulus) primarily consumed crabs, more so by larger than smaller fish. Inshore lizardfish (Synodus foetens) was almost entirely piscivorous. Ocellated flounder (Ancylopsetta ommata) consumed fishes, crabs, and stomatopods. Dwarf sand perch (Diplectrum bivittatum), blackwing searobin (Prionotus rubio), rock sea bass (Centropristis philadelphica), southern kingfish (Menticirrhus americanus), and red snapper (Lutjanus campechanus) fed mainly on shrimps. Most fish diets varied with respect to size (age), time of day, area sampled, depth, or season. Rimapenaeus and Sicyonia were the most frequently identified shrimp genera - only five Farfantepenaeus and no Litopenaeus were identified in almost 4,300 fish stomachs. I also examined gonadal development and documented fish length-weight relationships. Ripe gonads were most frequently found during summer in dwarf sand perch, during fall in ocellated flounder and bighead searobin, and during spring for other species, except no ripe red snapper or bank sea bass were collected. Rock sea bass was found to be a protogynous hermaphrodite, while dwarf sand perch is a synchronous hermaphrodite. Only ocellated flounder and southern kingfish exhibited sex-related differences in length-weight relationships. (PDF contains 40 pages.)

Estimation of the relative annual abundance of yellowfin tuna, Thunnus albacares, in the Eastern Pacific Ocean during 1970-1985

ENGLISH: Estimates of relative annual abundance of yellowfin tuna in the eastern Pacific Ocean during 1970-1985 are made using catch rates, measured as tons caught by purse seiners per hour of searching. Catch rates are standardized a weighted generalized linear model. The important standardizing factors are vessel speed, season-area, and whether the yellowfin were caught in association with dolphins, skipjack tuna, or floating objects. Observations are weighted to give equal areas equal weight and to give each unit of fishing effort equal weight within an area. The results indicate that catch per days fishing underestimates abundance during the late 1970's when the fishery shifted some of its effort from dolphin sets to floating object sets, and overestimates abundance when the fishery shifted back to dolphin sets in 1984 and 1985. SPANISH: Se estima la abundancia anual relativa del atún aleta amarilla en el Océano Pacífico oriental (OPO) durante 1970-1985 por medio de tasas de captura, calculadas como toneladas cortas capturadas por barcos cerqueros por hora de búsqueda. Se usa un modelo lineal ponderado generalizado para estandardizar las tasas de captura. Los factores importantes de estandardización son la velocidad del barco, temporada-área, y si se capturaron los aletas amarillas en asociación con delfines, barriletes, o objetos flotantes. Se ponderaron las observaciones para otorgar igual importancia a áreas iguales y a cada unidad de esfuerzo pesquero dentro de un área. Los resultados señalan que la captura por día de pesca estima por bajo la abundancia durante los últimos años de la década de los 70, en cual época la pesquería trasladó parte de su esfuerzo de lances sobre delfines a lances sobre objetos flotantes, y la sobreestima al volver la pesquería a lances sobre delfines en 1984 y 1985. (PDF contains 45 pages.)

Length weight relationship, condition factors and fecundity of Chrysichthys nigrodigitatus and Chrysichthys walkeri in Asejire Lake

Sex ratio and fecundity variations of Chrysichthys nigrodigitatus and Chrysichthys walkeri from Asejire Lake (Nigeria) were examined. The Logarithm transformation of weight (W) against standard length (SL) gave a straight-line graph represented by the following equations: 1) C. nigrodigitatus LogW =-0.66 + 2.13 Log SL; = 0.854; (P < 0.001) n = 209; 2) C. walkeri LogW = -1.23 + 2.63 Log SL; = 0.759; (P < 0.001) n = 237. Males were generally more than females in both species. The ratio of males:females was higher in C. nigrodigitatus (1:0.18) than in C. walkeri (1:0.8). C. walkeri attained sexual maturity at a smaller size of 20.0 g (12.0 cm Standard Length) compared with C. nigrodigitatus maturity size of 45.0 g (14.0 cm Standard Length). Relative fecundity was not dependent on body weight and standard length for C. walkeri but it was significant at P < 0.05 and P < 0.01 respectively for C. nigrodigitatus

Fishery resource surveys: beyond length-weight relationship models

Fisheries resource surveys are regular management tools for rational exploitation of commercial fisheries. In a growing number of cases, the use of these resource surveys has been largely restricted to assessment of the relative well being of fish stocks and the potential yields of such fisheries. This paper seeks to demonstrate that the data from such surveys can also be easily used to evaluate species diversity of such fisheries, both in terms of species richness and equitability of distribution. Using published data on two freshwater and two marine fisheries as case studies, Shannon-Wiener Diversity Function and Simpson's Index were computed for each of these fisheries. These biodiversity indices gave a deeper insight into the environmental status of each of these fisheries, beyond what the length-weight relationship models can reveal. Generally, while the marine fisheries showed more species richness, the freshwater fisheries apparently had more stable and equilibrated fish communities

Descripción de la morfología externa e interna del langostino con algunas aplicaciones de indole taxonómica y biológica

In the present paper the external and internal morphology of the shrimp Pleoticus muelleri (Bate), is described in detail. Special attention is given to those features which are of diagnostic value or which are significant for a fuller understanding of the biology of this species. The major portion of the paper deals with the description of the cephalopereion, pleon and telson and its appendages, as well as the nervous, respiratory, circulatory, digestive, excretory and reproductive systems. Special attention is given to the digestive system, the stomodaeal apparatus and sexual dimorphism. The relations between form and function of several organs and systems are pointed out. A study is made of the development of the gonads, the sexual cycle in males and females; the variations found in relative weight and size are described. The phylogenetical jposition of the Penaeidae, the genera of the subfamily Solenoceridae and of P. muelleri are discussed. (PDF contains 72 pages)

Weight-fecundity relationships of Nigerian fish populations

Parameters a and b of the power body weight (W) - fecundity (F=a W super(b)) are presented for 25 populations comprising 15 species of Nigerian fishes. Estimates of b varied between 0.511 (Parauchenoglanis akin) and 1.654 (Periophthalmus barbarus) with a mean of 1.087 (s.d.=0.520). The maximum weight of populations examined did not significantly influence the relative magnitude of b. The parameters proportional to and beta of the linear weight-fecundity relationship (F= proportional to + beta W) are also presented for 27 fish populations from 22 species. Estimates of beta ranged from 4.22 (Chromidotilapia guntheri) to 2,062.94 (Pellunula min), with a mean of 243.80 (s.d.=477.89). The magnitude of beta declined with increasing maximum weights of fishes examined.

Length-weight relationships for some important forage crustaceans from South Africa

The diet of marine animals is usually determined by stomach content analysis. Although partially digested prey fragments can often be identified to species level, it is difficult to estimate the original mass of the prey organism. This information, however, is essential for calculating both the total food intake as well as the relative contribution of each prey item. In this study we present regression equations that can be used to estimate the original mass of 18 common South African crustaceans from various indigestible fragments such as the carapace (length and width), chelae (length and width of left and right dactylus) and eye (length and width).