Cephalopod Resources of Venezuela

The cephalopod resources of Venezuela are reviewed, based on previous literature and observations from commercial catches. The history of the squid and octopus fishery in the major fishing grounds is presented along with information on the catches and seasonality. Squids are landed in Venezuela throughout the year, with a high in February when most of the catch consists of the arrow squid, Doryteuthis plei. Octopus, Octopus vulgaris, is abundant in the catches from June until October, with a peak in August-September. Methods of handling, processing, and marketing the cephalopod catch are discussed, and correctional guidelines are given. At present, the fishery is in disarray and there is an urgent need for study of Venezuela's commercial cephalopods

Swordfish Reproduction in the Atlantic Ocean: An Overview

There are 3 unit stocks of Atlantic swordfish, Xiphias gladius, separated into Mediterranean, North and South Atlantic with no precise delimitation between them, and each contains its spawning grounds far from stock boundary areas. This overview characterizes the reproductive information for each stock unit and describes reproductive metrics in detail. Spawning in the western North Atlantic consists of 2 spawning groups: one in open ocean waters and the other in waters close to land masses and fast current systems. Spawning occurs from December to June within the subtropical area (13°N-35°N). Within the Mediterranean, spawning takes place between June and August, and appears to be restricted between 35°N and 40°N. The information for the South Atlantic is limited, but spawning concentrations are present in April-June on the western side off Brazil and the equatorial area, and from October to March in the central-eastern equatorial area. In the western North Atlantic, females are observed to mature at larger sizes (Mf50 =178.7 cm) and older ages (age 5.03) than in the South Atlantic (Mf50 = 156 cm) and Mediterranean Sea (Mf50 = 142.2 cm). Estimates of batch fecundities in swordfish in the Atlantic Ocean appear to be similar, and can reach up to 8-9.9 million eggs per spawn

Revisión de Libros

CEPHALOPOD LIFE CYCLES, Vol. 11. Comparative reviens. Peter R. Boyle (Editor). Academic Press, Londres, 1987. (464 páginas) $ 140,oo lL. E. 78,oo

Análisis multimodelo del crecimiento de pseudoplatystoma orinocoense en la cuenca media del Orinoco, Venezuela

Among the species of greater commercial and fishing importance of the artisanal fishery of the Orinoco River is Pseudopatystoma orinocoense, where the disembarkation of small fish motivated the realization of previous studies of evaluation of its population, which demonstrated a level of overexploitation of the resource. However, the values of the growth parameters that were used in their evaluation have created some uncertainty to be estimated when applying the traditional von Bertalanffy model a priori, so there was a need to verify these results, using the inference of multiple models of Growth and Akaike Information Criteria (AIC) to select the best fit model. The models used were the unified formulas von Bertalanffy (U-von Bertalanffy), Logistic (U-Logistic) and Gompertz (U-Gompertz), derived from the generic model U-Richardas, whose adjustments depended on the information contained in the data. When the data included all ages, the U-von Bertalanffy model produced the best fit, coinciding with previous results of growth of the species. By excluding the ages of one and two years, as occurs with data from artisanal fishing due to selectivity, the best fit was produced by the U-Logistic and U-Gompertz. models.Entre las especies de mayor importancia comercial y pesquera de la pesca artesanal del rio Orinoco se encuentra Pseudopatystoma orinocoense, donde el desembarco de peces pequeños motivó la realización de estudios anteriores de evaluación de su población, que demostraron un nivel de sobreexplotación del recurso. Sin embargo, los valores de los parámetros de crecimiento que se usaron en su evaluación han creado cierta incertidumbre por estimarse al aplicar a priori el modelo tradicional de von Bertalanffy, por lo que hubo la necesidad de verificar dichos resultados, utilizando la inferencia de modelos múltiples de crecimiento y el criterio de la información de Akaike (AIC) para seleccionar el modelo de mejor ajuste. Los modelos usados fueron las fórmulas unificadas von Bertalanffy (U-von Bertalanffy), Logístico (U-Logístico) y Gompertz (U-Gompertz), derivados del modelo genérico U-Richardas, cuyos ajustes dependieron de la información contenida en los datos. Cuando los datos incluyeron todas las edades el modelo U-von Bertalanffy produjo el mejor ajuste, coincidiendo con resultados anteriores de crecimiento de la especie. Al excluir  las edades de uno y dos años, como ocurre con  los datos provenientes de la pesca artesanal debido a la selectividad, el mejor ajuste lo produjeron los modelos U-Logístico y U-Gompertz. Instituto Limnológico, Universidad de Oriente, Departamento de Recursos Acuáticos, Dinámica Poblacional de Peces Continentales. MsC Biología Pesquera.

Comparative Population Genetics and Evolutionary History of Two Commonly Misidentified Billfishes of Management and Conservation Concern

Background: Misidentifications between exploited species may lead to inaccuracies in population assessments, with potentially irreversible conservation ramifications if overexploitation of either species is occurring. A notable showcase is provided by the realization that the roundscale spearfish (Tetrapturus georgii), a recently validated species, has been historically misidentified as the morphologically very similar and severely overfished white marlin (Kajikia albida) (IUCN listing: Vulnerable). In effect, no information exists on the population status and evolutionary history of the enigmatic roundscale spearfish, a large, highly vagile and broadly distributed pelagic species. We provide the first population genetic evaluation of the roundscale spearfish, utilizing nuclear microsatellite and mitochondrial DNA sequence markers. Furthermore, we re-evaluated existing white marlin mitochondrial genetic data and present our findings in a comparative context to the roundscale spearfish. Results: Microsatellite and mitochondrial (control region) DNA markers provided mixed evidence for roundscale spearfish population differentiation between the western north and south Atlantic regions, depending on marker-statistical analysis combination used. Mitochondrial DNA analyses provided strong signals of historical population growth for both white marlin and roundscale spearfish, but higher genetic diversity and effective female population size (1.5-1.9X) for white marlin. Conclusions: The equivocal indications of roundscale spearfish population structure, combined with a smaller effective female population size compared to the white marlin, already a species of concern, suggests that a species-specific and precautionary management strategy recognizing two management units is prudent for this newly validated billfish

Broad Geographic Distribution of Roundscale Spearfish (Tetrapturus georgii) (Teleostei, Istiophoridae) in the Atlantic Revealed by DNA Analysis: Implications for White Marlin and Roundscale Spearfish Management

The recent validation of the roundscale spearfish (Tetrapturus georgii) within the western North Atlantic has introduced new complexities in the management of the overfished white marlin (Kajikia albida) in this region due to historical and contemporary misidentification between the two morphologically similar species. Compounding the management challenge for white marlin, which is currently assessed as a single Atlantic-wide stock, is an unclear picture of the extent of the roundscale spearfish\u27s overall Atlantic distribution. By using genetic tools (mitochondrial DNA ND4L-ND4 locus sequences) for species identification, we confirm that the roundscale spearfish has a much broader distribution than previously known, including the central North Atlantic and much of the western South Atlantic to at least 28°52′S. This much wider Atlantic distribution of the roundscale spearfish sympatric with its morphologically similar congeners, the white marlin and longbill spearfish (Tetrapturus pfluegeri), raises further management complexities: it increases the geographic scale for species misidentification in catch records that form the basis for stock assessments and uncertainty in currently accepted white marlin biological parameters. Additional vigilance in obtaining accurate species identification by improved fishery onboard observer training and incorporation of genetic tools is recommended for informing management of white marlin, longbill spearfish and roundscale spearfish throughout the Atlantic

Population structure, catch composition and CPUE of the artisanally harvested mangrove crab Ucides cordatus(Ocypodidae) in the Caeté estuary, North Brazil: Indications for overfishing?

To evaluate the population structure of Ucides cordatus in the Caeté estuary, crabs were sampled bimonthly over 13 months in three Rhizophora mangle forest stands that differed in their accessibility and fishing history. Additionally, sex- and size composition of the commercial catch and catch per unit of effort (CPUE – the number of crabs captured per fisherman per day) were monitored between 1997 and 2003. Average and maximum crab sizes (carapace width, CW) from all three sampling sites combined were 6.1 cm and 8.8 cm in males, respectively, and 5.5 and 7.3 cm in females. Crabs were largest at the site that had been reportedly less exploited in the past. The overall sex ratio was skewed towards males (53−62%). Egg carrying females were only encountered during the rainy season. Mean crab abundance and biomass was 1.7 specimens m−2 and 142 g m−2 fresh mass. Only large males were commercially harvested (98% ≥ 6.5 cm CW). Their biomass was 53 g m−2 and the Caeté estuary yields an annual production of 1200 t of these large specimens. This is approximately the quantity that is currently being harvested. CPUE was similar in 1997 and 1998, then decreased by 15% until 2000 and stabilized for the rest of the study period. Mean capture size (cm CW) ranged between 7.2 ± 0.5 and 7.5 ± 0.2 and was above the size of 50% (and even 100%) male maturity and the legal minimum capture size. There is no evidence that the Caeté crab population is overfished, despite over 30 years of de facto open access exploitation. Apparently, the selectivity of fishermen and consumers for large male crabs as well as the local artisanal capture techniques are key factors in preventing an overfishing of the Caeté crab population until today. Our results suggest that the economic and social sustainability of this fishery will be affected well before the biological one, which should be considered in the recently proposed coastal co-management plan for the region

Seascape genomics and phylogeography of the sailfish (Istiophorus platypterus)

Permeable phylogeographic barriers characterize the vast open ocean, boosting gene flow and counteracting population differentiation and speciation of widely distributed and migratory species. However, many widely distributed species consists of distinct populations throughout their distribution, evidencing that our understanding of how the marine environment triggers population and species divergence are insufficient. The sailfish is a circumtropical and highly migratory billfish that inhabits warm and productive areas. Despite its ecological and socioeconomic importance as a predator and fishery resource, the species is threatened by overfishing, requiring innovative approaches to improve their management and conservation status. Thus, we presented a novel high-quality reference genome for the species and applied a seascape genomics approach to understand how marine environmental features may promote local adaptation and how it affects gene flow between populations. We delimit two populations between the Atlantic and Indo-Western Pacific oceans and detect outlier loci correlated with sea surface temperature, salinity, oxygen, and chlorophyll concentrations. However, the most significant explanatory factor that explains the differences between populations was isolation by distance. Despite recent population drops, the sailfish populations are not inbred. For billfishes in general, genome-wide heterozygosity was found to be relatively low compared to other marine fishes, evidencing the need to counteract overfishing effects. In addition, in a climate change scenario, management agencies must implement state-of-the-art sequencing methods, consider our findings in their management plans, and monitor genome-wide heterozygosity over time to improve sustainable fisheries and the long-term viability of its populations.LA/P/0101/2020info:eu-repo/semantics/publishedVersio

A typology of fisheries management tools: using experience to catalyse greater success

Fisheries provide nutrition and livelihoods for coastal populations, but many fisheries are fully or over-exploited and we lack an approach for analysing which factors affect management tool performance. We conducted a literature review of 390 studies to assess how fisheries characteristics affected management tool performance across both small-scale and large-scale fisheries. We defined success as increased or maintained abundance or biomass, reductions in fishing mortality or improvements in population status. Because the literature only covered a narrow set of biological factors, we also conducted an expert elicitation to create a typology of broader fishery characteristics, enabling conditions and design considerations that affect performance. The literature suggested that the most commonly used management tool in a region was often the most successful, although the scale of success varied. Management tools were more often deemed successful when used in combination, particularly pairings of tools that controlled fishing mortality or effort with spatial management. Examples of successful combinations were the use of catch limits with quotas and limited entry, and marine protected areas with effort restrictions. The most common factors associated with inadequate biological performance were ‘structural’ issues, including poor design or implementation. The expert-derived typologies revealed strong local leadership, high community involvement and governance capacity as common factors of success across management tool categories (i.e. input, output and technical measures), but the degree of importance varied. Our results are designed to inform selection of appropriate management tools based on empirical data and experience to increase the likelihood of successful fisheries management.Department of HE and Training approved lis