Étude préliminaire sur l'incorporation de liants dans un aliment composé pour poisson d'élevage en Côte d'Ivoire

Artificial feeding constitutes a very important aspect for intensive fish culture. Then, the physical properties, particularly water stability of feed, wider influence the fish production. By trying to find some answers to these problems, a preliminary study on water stability has been conducted at the LAYO aquaculture research station. This work consisted in incorporating different types of binders available in tropical countries in fish pellets of 3.5 mm and 6.0 mm diameters in order to identify an efficient binder allowing the improvement of the water stability of feed. From this experiment, it comes out that the use of wheat flour (A1) gives excellent quality pellets followed by cassava flour residue (A3). Moreover, this study shows that it exists an influence of the diameter on the crumbling of the pellets.

Toxicité des sulfures dissous chez le poisson-chat africain, Heterobranchus longifilis (Valenciennes, 1840)

Biological tests were carried out using static bioassay systems to determine the median lethal concentration of total sulfide (H2S, HS, S2) for African catfish (Heterobranchus longifilis, Valenciennes, 1840) at fry and juvenile stages.

Croissance et détermination de l'âge par lecture d'écailles d'un poisson plat de Côte d'Ivoire, Cynoglossus canariensis (Steind. 1882)

Cynoglossus canariensis has a very rapid growth. The rate of the males is 0,36 and the female one is 0,32. The asymptotic size is 55,0cm for the females and 50,5cm for the males. Females and males younger than three years (40cm), which represent 90 per cent of the Côte d'Ivoire stock have a similar growth, so the average equation: Lt=53,5 (1-e -0,34(t+1)) will be used.

Capture d'un Requin-Baleine, Rhineodon typus A. Smith, en Cohinchine: résumé de connaissances sur ce poisson

A description of a whale shark (Rhincodon typus) captured on June 1934 along the coast of Cap Ti Oan is given. The scientific name Rhincodon is not correct due to a typographic error. The name with greek origin, should be: Rhineodon typus.

Etude de la chaine de commercialisation du poisson: Lac Ntomba, section du fleuve Congo (Ngombe) et marchés de Mbandaka et Kinshasa

Cette étude a été réalisée par le WorldFish Center dans le cadre de sa collaboration avec le WWF et le projet CARPE de l’USAID. La chaîne de commercialisation du poisson a été suivie des zones de production jusqu’au principal marché final. La région au centre de cette étude est le lac Ntomba ainsi qu’une partie du fleuve Congo. Ceci correspond à la partie nord de la section du Paysage Lac Télé - Lac Tumba de la République Démocratique du Congo. Toutes les étapes de la chaîne de commercialisation du poisson ont été prises en compte dans cette étude. Les stratégies des acteurs présents à chaque étape ainsi que les dynamiques les associant à la chaîne ont été utilisées pour refléter le fonctionnement de la chaîne de commercialisation du poisson et identifier ses spécificités. La pêche est une activité saisonnière de grande importance dans la région du lac Ntomba et la partie proche du fleuve Congo. La majorité des habitants de la région constituent leurs moyens d’existence d’un panachage d’activités, dont la séquence semble être rythmée essentiellement par l’opportunité et le climat. Presque aucun service n’est offert dans cette région où les activités économiques sont réduites et n’ont le plus souvent qu’une faible productivité. Cependant, la chaîne de commercialisation du poisson supporte un large éventail d’acteurs différents et représente un secteur d’une grande importance pour la région. Cette région périphérique est reliée au reste de l’économie nationale par une série de marchés et de nombreux différents types d’acteurs. Assurer ce lien représente de sérieuses difficultés et comporte des risques importants tandis que les marges de profits sont le plus souvent minces. Cependant, il semblerait que, de manière générale, le marché se développe et les liens se renforcent, même si cette évolution est plus discrète dans les lieux les plus isolés.

Effects of lunar cycle and fishing operations on longline-caught pelagic fish: fishing performance, capture time, and survival of fish

Commercial longline fishing data were analyzed and experiments were conducted with gear equipped with hook timers and timedepth recorders in the Réunion Island fishery (21°5ʹS lat., 53°28ʹE long.) to elucidate direct and indirect effects of the lunar cycle and other operational factors that affect catch rates, catch composition, fish behavior, capture time, and fish survival. Logbook data from 1998 through 2000, comprising 2009 sets, indicated that swordfish (Xiphias gladius) catch-per unit of effort (CPUE) increased during the first and last quarter of the lunar phase, whereas albacore (Thunnus alalunga) CPUE was highest during the full moon. Swordfish were caught rapidly after the longline was set and, like bigeye tuna (Thunnus obesus), they were caught during days characterized by a weak lunar illumination—mainly during low tide. We found a significant but very low influence of chemical lightsticks on CPUE and catch composition. At the time the longline was retrieved, six of the 11 species in the study had >40% survival. Hook timers indicated that only 8.4% of the swordfish were alive after 8 hours of capture, and two shark species (blue shark [Prionace glauca] and oceanic whitetip shark [Carcharhinus longimanus]) showed a greater resilience to capture: 29.3% and 23.5% were alive after 8 hours, respectively. Our results have implications for current fishing practices and we comment on the possibilities of modifying fishing strategies in order to reduce operational costs, bycatch, loss of target fish at sea, and detrimental impacts on the environment.

The statistical properties of recreational catch rate data for some fish stocks off the northeast U.S. coast

Recreational fisheries in the waters off the northeast U.S. target a variety of pelagic and demersal fish species, and catch and effort data sampled from recreational fisheries are a critical component of the information used in resource evaluation and management. Standardized indices of stock abundance developed from recreational fishery catch rates are routinely used in stock assessments. The statistical properties of both simulated and empirical recreational fishery catch-rate data such as those collected by the National Marine Fisheries Service (NMFS) Marine Recreational Fishery Statistics Survey (MRFSS) are examined, and the potential effects of different assumptions about the error structure of the catch-rate frequency distributions in computing indices of stock abundance are evaluated. Recreational fishery catch distributions sampled by the MRFSS are highly contagious and overdispersed in relation to the normal distribution and are generally best characterized by the Poisson or negative binomial distributions. The modeling of both the simulated and empirical MRFSS catch rates indicates that one may draw erroneous conclusions about stock trends by assuming the wrong error distribution in procedures used to developed standardized indices of stock abundance. The results demonstrate the importance of considering not only the overall model fit and significance of classification effects, but also the possible effects of model misspecification, when determining the most appropriate model construction.

On statistical comparison of efficiencies of fishing gear

The distribution of fish caught by experimental gill nets has been found to be in the Poisson or Negative binomial form. Using this information, application of Chi-square test as suggested by Mood et al. (1974) has been illustrated, for comparing the efficiencies of gill nets. This test provides an alternative to Anova F-test especially in the context of significance of non-additivity for the two-way model. Based on the present work and the findings by Nair (1982) and Nair & Alagaraja (1982, 1984) an outline approach for statistical comparison of the efficiencies of fishing gear is presented.