Escala de madurez gonadal de cabrilla Paralabrax humeralis (Valenciennes, 1828)

Se realiza la validación de la escala de madurez gonadal macroscópica de la cabrilla Paralabrax humeralis. Se analizaron 197 ovarios y 188 testículos provenientes del seguimiento de la pesquería demersal y cruceros de investigación de recursos demersales en el 2005 (Enero-febrero y mayo-junio). Sobre la base del análisis histológico se asignó a cada individuo un estadio de madurez macroscópico. Se realizó la descripción de los estadios de madurez que van desde el estadio 0 (virginal) hasta el 5 (recuperación en hembras, post expulsante en machos). Se realizó una comparación con escalas anteriormente realizadas, discutiendo además los beneficios de su uso.

Algunos aspectos adicionales sobre la biología y pesquería del falso volador Prionotus stephanophrys

Presenta aspectos biológico pesqueros del falso volador Prionotus stephanophrys Lockington sobre la base de la información biométrica (1997-1999), biológica (1988-1991 y 1997-1999), desembarques (1970-1999) y volúmenes de exportaciones. Identifica al falso volador como el segundo pez en importancia del subsistema bentodemersal después de la merluza (Merluccius gayi peruanus), ubicándose masivamente en áreas no ocupadas por la merluza.

Modelling discard ogives from Irish demersal fisheries

Annual discard ogives were estimated using generalized additive models (GAMs) for four demersal fish species: whiting, haddock, megrim, and plaice. The analysis was based on data collected on board commercial vessels and at Irish fishing ports from 1995 to 2003. For all species the most important factors influencing annual discard ogives were fleet (combination of gear, fishing ground, and targeted species), mean length of the catch and year, and, for megrim, also minimum landing size. The length at which fish are discarded has increased since 2000 for haddock, whiting, and plaice. In contrast, discarded length has decreased for megrim, accompanying a reduction in minimum landing size in 2000.

Sustentabilidad de la Pesquería Artesanal del Río Bermejo.

Este trabajo es el resultado de la tesis de Maestría en Recursos Naturales y Medio Ambiente (Orientación Recursos Faunísticos), realizada por el autor en la Facultad de Ciencias Naturales de la Universidad Nacional de Salta y bajo la dirección del Dr. Sergio Gustavo Mosa. La pesca artesanal con fines comerciales es practicada en el sector salteño del Río Bermejo desde hace décadas, por pobladores de localidades ribereñas como Orán, Embarcación y Rivadavia Banda Sur, los cuales pescan hasta el límite Salta – Chaco, dependiendo de la época del año. Esta pesquería se desarrolló por más de 50 años fuera del marco de las normas legales vigentes en la provincia (Ley 5513), siendo una actividad marginal perseguida por la justicia, y mal vista por la opinión pública en general. Entre Julio de 2001 y Julio de 2003, la Cooperativa de Pescadores Artesanales “La Unión” fue habilitada como empresa pesquera comercial de tipo artesanal por la Secretaria de Medio Ambiente y Desarrollo Sustentable de Salta. El monitoreo de esta actividad fue efectuado por la Cátedra de Piscicultura y Pesquerías (IRNED) de la Facultad de Ciencias Naturales de la Universidad Nacional de Salta. Las reglamentaciones y regulaciones legales de esta actividad se tomaron originariamente bajo el principio de precaución ante la falta de conocimiento científico. A la luz de la nueva información colectada, algunas de ellas resultan contrarias al principio prioritario de la gestión pesquera, el cual propone: Obtener la mejor utilización posible del recurso en provecho de la comunidad, recordando que mejor utilización implica mayor captura, mejor precio, más ganancias y más empleo. La presente Tesis de Maestría demuestra la sustentabilidad de la pesquería artesanal en el Bermejo, tanto desde a) el punto de vista biológico, analizando las capturas en función de las normas y reglamentaciones legales vigentes y de la biología y hábitos reproductivos de cada especie, como desde b) el punto de vista económico, teniendo en cuenta la relación costo-beneficio y las posibles alternativas para optimizar la misma. Asimismo, formula una serie de recomendaciones destinadas a mejorar la gestión pesquera. Para las 4 especies más importantes de la pesquería: sábalo Prochilodus lineatus, surubí Pseudoplatystoma coruscans, dorado Salminus brasiliensis y bagre blanco Pimelodus albicans, a) los cupos asignados para la captura anual por especie no son alcanzados; b) las tallas mínimas de captura observadas superan las tallas mínimas de captura autorizadas; c) las tallas medias de captura se encuentran muy por encima de las tallas medias de madurez sexual; d) la captura exclusiva de ejemplares maduros para todas las especies prueba que el grueso del stock pesquero ha podido superar por lo menos un evento reproductivo antes de ser capturado; e) el actual período de veda resulta demasiado amplio por lo que uno de dos meses, de mediados de noviembre a mediados de enero resultaría biológicamente adecuado. En cuanto a la sustentabilidad económica de la actividad, cada unidad económica de pesca debe realizar entre 45 y 50 excursiones de pesca anuales para obtener rendimientos económicos equivalentes a un ingreso mensual de aproximadamente $ 1000. (PDF tiene 92 paginas.)

Biología pesquera de las lagunas Encadenadas del Sudoeste, provincia de Buenos Aires.

El objetivo es definir las variables biológicas del pejerrey (Odonthesthes bonariensis)de las lagunas del sistema para detectar el posible impacto de las obras hidraúlicas proyectadas en la región y evaluar las características de transición del área estudiada desde el punto de vista de la composición ictiofaunística. El presente artículo es una reedición del generado por el Departamento Científico Zoología Vertebrados (actual División Zoología Vertebrados), FCNyM, UNLP, en noviembre de 1993. El anexo 7.1-Fotografías fue omitido debido a la mala calidad de las imágenes.

Variations in eastern North Pacific demersal fish biomass based on the U.S. west coast groundfish bottom trawl survey (2003–2010)

In response to declining biomass of Northeast Pacific groundfish in the late 1990s and to improve the scientific basis for management of the fishery, the Northwest Fisheries Science Center standardized and enhanced their annual bottom trawl survey in 2003. The survey was expanded to include the entire area along the U.S. west coast at depths of 55–1280 m. Coast-wide biomass and species richness significantly decreased during the first eight years (2003–10) of this fishery-independent survey. We observed an overall tendency toward declining biomass for 62 dominant taxa combined (fishery target and nontarget species) and four of seven subgroups (including cartilaginous fish, flatfishes, shelf rockfishes, and other shelf species), despite increasing or variable biomass trends in individual species. These decreases occurred during a period of reduced catch for groundfish along the shelf and upper slope regions relative to historical rates. We used information from multiple stock assessments to aggregate species into three groups: 1) with strong recruitment, 2) without strong recruitment in 1999, and 3) with unknown recruitment level. For each group, we evaluated whether declining biomass was primarily related to depletion (using year as a proxy) or environmental factors (i.e., variation in the Pacific Decadal Oscillation). According to Akaike’s information criterion, changes in aggregate biomass for species with strong recruitment were more closely related to year, whereas those with no strong recruitment were more closely related to climate. The significant decline in biomass for species without strong recruitment confirms that factors other than depletion of the exceptional 1999 year class may be responsible for the observed decrease in biomass along the U.S. west coast.

Season- and depth-dependent variability of a demersal fish assemblage in a large fjord estuary (Puget Sound, Washington)

Fjord estuaries are common along the northeast Pacific coastline, but little information is available on fish assemblage structure and its spatiotemporal variability. Here, we examined changes in diversity metrics, species biomasses, and biomass spectra (the distribution of biomass across body size classes) over three seasons (fall, winter, summer) and at multiple depths (20 to 160 m) in Puget Sound, Washington, a deep and highly urbanized fjord estuary on the U.S. west coast. Our results indicate that this fish assemblage is dominated by cartilaginous species (spotted ratfish [Hydrolagus colliei] and spiny dogfish [Squalus acanthias]) and therefore differs fundamentally from fish assemblages found in shallower estuaries in the northeast Pacific. Diversity was greatest in shallow waters (<40 m), where the assemblage was composed primarily of flatfishes and sculpins, and lowest in deep waters (>80 m) that are more common in Puget Sound and that are dominated by spotted ratf ish and seasonally (fall and summer) by spiny dogfish. Strong depth-dependent variation in the demersal fish assemblage may be a general feature of deep fjord estuaries and indicates pronounced spatial variability in the food web. Future comparisons with less impacted fjords may offer insight into whether cartilaginous species naturally dominate these systems or only do so under conditions related to human-caused ecosystem degradation. Information on species distributions is critical for marine spatial planning and for modeling energy flows in coastal food webs. The data presented here will aid these endeavors and highlight areas for future research in this important yet understudied system.

Day and night abundance, distribution, and activity patterns of demersal fishes on Heceta Bank, Oregon

Most shallow-dwelling tropical marine fishes exhibit different activity patterns during the day and night but show similar transition behavior among habitat sites despite the dissimilar assemblages of the species. However, changes in species abundance, distribution, and activity patterns have only rarely been examined in temperate deepwater habitats during the day and night, where day-to-night differences in light intensity are extremely slight. Direct-observation surveys were conducted over several depths and habitat types on Heceta Bank, the largest rocky bank off the Oregon coast. Day and night fish community composition, relative density, and activity levels were compared by using videotape footage from a remotely operated vehicle (ROV) operated along paired transects. Habitat-specific abundance and activity were determined for 31 taxa or groups. General patterns observed were similar to shallow temperate day and night studies, with an overall increase in the abundance and activity of fishes during the day than at night, particularly in shallower cobble, boulder, and rock ridge habitats. Smaller schooling rockfishes (Sebastes spp.) were more abundant and active in day than in night transects, and sharpchin (S. zacentrus) and harlequin (S. variegatus) rockfish were significantly more abundant in night transects. Most taxa, however, did not exhibit distinct diurnal or nocturnal activity patterns. Rosethorn rockfish (S. helvomaculatus) and hagfishes (Eptatretus spp.) showed the clearest diurnal and nocturnal activity patterns, respectively. Because day and night distributions and activity patterns in demersal fishes are likely to influence both catchability and observability in bottom trawl and direct-count in situ surveys, the patterns observed in the current study should be considered for survey design and interpretation.

Multiscale habitat associations of deepwater demersal fishes off central California

Fish-habitat associations were examined at three spatial scales in Monterey Bay, California, to determine how benthic habitats and landscape configuration have structured deepwater demersal fish assemblages. Fish counts and habitat variables were quantified by using observer and video data collected from a submersible. Fish responded to benthic habitats at scales ranging from cm’s to km’s. At broad-scales (km’s), habitat strata classified from acoustic maps were a strong predictor of fish assemblage composition. At intermediate-scales (m’s−100 m’s), fish species were associated with specific substratum patch types. At fine-scales (<1 m), microhabitat associations revealed differing degrees of microhabitat specificity, and for some species revealed niche separation within patches. The use of habitat characteristics in ecosystembased management, particularly as a surrogate for species distributions, will depend on resolving fish-habitat associations and habitat complexity over multiple scales.

Diet composition and food habits of demersal and pelagic marine fishes from Terengganu waters, east coast of Peninsular Malaysia

Fish stomachs from 18 demersal and pelagic fishes from the coast of Terengganu in Malaysia were examined. The components of the fishes’ diets varied in number, weight, and their frequency of occurrence. The major food items in the stomachs of each species were determined using an Index of Relative Importance. A conceptual food web structure indicates that fish species in the study area can be classified into three predatory groups: (1) predators on largely planktivorous or pelagic species; (2) predators on largely benthophagous or demersal species; and (3) mixed feeders that consume both pelagic and demersal species.

Length-weight relationships of demersal fishes from the upper continental slope off Colombia

Parameters of the length–weight relationship of the form W=aLb are presented for 45 demersal fish species caught on the upper continental slope of the Caribbean Sea off Colombia. The b values varied between 2.13 and 4.97, with the mean b = 3.042 (95% CI, 2.887- 3.196).

Length-weight relationships of demersal fishes from the Gulf of Salamanca, Colombia: [part 2]

The parameters a and b of the length-weight relationship of the form W=aL super(b) are presented for 37 fish species, belonging to 17 families, caught during a demersal trawl survey over the period December 1995 to March 1998 in the Gulf of Salamanca, Colombia

Length-weight relationships of demersal fishes from the Gulf of Salamanca, Colombia

The parameters a and b of the length-weight relationship of the form W=a L super(b) were computed for 46 species caught in a series of demersal trawl hauls over the period 1995-1997 in the Gulf of Salamanca, Colombia.

The small-scale pelagic and demersal fisheries off Kribi, Cameroon

A description of the small-scale fisheries of the coastal pelagic and demersal resources off Kribi, Cameroon, is presented. The major fishing grounds are within the estuarine zone, an area of high productivity. Catch estimates of 19.5 t year super(-1) and 6.5 t year super(-1) were obtained for the pelagic motorized and nonmotorized canoes, respectively, while estimates of 11 t year super(-1) were obtained for the demersal motorized canoes. The social benefits from these fisheries are also discussed.