Marine and Fishery Sciences (MAFIS)

Patagonian toothfish (Dissostichus eleginoides) stocks in South American waters and its implications for fishery management

2024-12-02T17:48:28+00:00

Patagonian toothfish (Dissostichus eleginoides) is a highly prized resource in markets due to the quality of its meat. The Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR) implemented controls and regulations in response to the sharp rise in the illegal fishing of D. eleginoides in the 1990s. Today, four fisheries in waters close to the southern tip of South America are managed in accordance with stringent sustainability standards. Even though they are separate management units, both abundance assessments and annual catch allocations are conducted using different criteria regarding stock considerations across the region, leaving one of the fundamental premises of fisheries management unclear. This study examines historical data and recent research to explore the potential differentiation between Patagonian toothfish populations in South American waters, which is crucial for the management of diverse fisheries. Genetic studies, otolith microchemistry, morphometry, parasitic fauna, tagging programs, reproductive characteristics, and the impact of ocean circulation on dispersal and recruitment were analyzed. Tagging studies in the southern hemisphere oceans confirm the species’ affinity to specific habitats, suggesting minimal fish exchange between South American fishing grounds. From a fisheries perspective, this review suggests the existence of distinct stocks of the species structured along the shelf and slope of the southern cone of America based on reproduction areas along the continental shelves and slope, the diverse parasitic fauna, the variability in stable isotopes and trace elements of otoliths, and the little significant exchange of fish between current fishing grounds. All of this could lead to considering the D. eleginoides fishery as independent exploitation units.

Biosecurity protocols and fish health management in Kenyan fish hatcheries: a key to sustainable production of quality fish seed

2024-07-15T16:22:39+00:00

Aquaculture, or aquafarming, is increasingly becoming a vital farming activity globally to meet exponentially high demand for fish and reduce pressure on global capture fisheries. In Kenya, aquaculture growth has led to concerns over the supply of quality fish seed, with farmers often reporting involving fingerling adulteration and mislabelling where frog tadpoles are packed and supplied as Clarias gariepinus fingerlings and mixed-sex Oreochromis niloticus fingerlings are falsely sold to fish farmers as sex-reversed monosex Nile tilapia. This study aims to identify strategies to enhance the quality of fish seed production in the country. Primary data were collected via questionnaires and interviews using the Kobo toolbox. Respondents were selected through purposive and random sampling. The SPSS software was used for the analysis. Findings showed moderate reliance on specific reporting offices for fish disease cases and significant variation in disease types and bio security measures. Fish disease treatment and management practices were more engaged by hatchery operators than disease reporting. No significant differences were found between disease treatment and management, type of fish diseases encountered at the hatchery, and the nature of fingerlings produced (p > 0.05). However, there was a significant difference between the source of broodstock, biosecurity measures, type of fish diseases encountered, and the Disease Case Reporting Office (p < 0.05). No significant difference was found between biosecurity measures and the period when the hatchery was established (p > 0.05). Lack of financial support, inexperienced workforce, and a lack of knowledge in fish disease identification and treatment were the major problems affecting the sustainability of hatchery operations in the country. Aquaculture policymakers should establish financial support for hatcheries, implement disease management training, promote research collaborations for disease surveillance, and incentivize biosecurity measures among hatchery managers and farmers to improve aquaculture sustainability in Kenya. Further research should explore treatment methods and long-term sustainability to mitigate disease risks.

Status and characteristics of sharks and rays impacted by artisanal fisheries: potential implications for management and conservation

2024-07-26T12:11:29+00:00

Artisanal fisheries in Kenya face substantial challenges, including inadequate enforcement, absence of tailored regulations for elasmobranch conservation and lack of robust data collection systems, hampering our understanding of fisheries and biological aspects of species. To address these challenges, this study examined the species composition, size, weight and number of shark and ray landings in three sites historically known for large catches of elasmobranchs. This research aimed to characterise Kenyan elasmobranchs fishery and exhibit its overlap with key habitats. Our findings are worrying since 79% of the landed fisheries species are categorised as threatened on the IUCN Red List. This includes the Critically Endangered scalloped hammerhead shark (Sphyrna lewini) and white-spotted guitarfish (Rhynchobatus djiddensis), both species frequently caught. Further, 97% of sharks and 46% of rays are landed as neonate and immature individuals. Urgent changes are imperative in national fisheries management to prevent the potential local disappearance of several shark and ray species. We recommend specific conservation measures to reduce the capture of threatened species and juveniles, such as banning the landing of threatened species and establishing minimum size limits. Enforcing fisheries regulations, such as mesh size, and prioritizing the protection of key habitats for the most at-risk species are essential proactive steps.

Relative abundance and use of elasmobranchs in artisanal fisheries of the Lesser Antilles

2024-08-09T14:09:50+00:00

Shark and ray populations continue to decline in many regions around the world. The contribution of artisanal fisheries to these declines remains poorly understood for many locations. A rapid assessment framework using fisheries-independent sampling and fisher interviews was employed to study elasmobranch occurrence and use in coastal artisanal fisheries of Guadeloupe, Martinique, and Tobago. In-person interviews (n = 405) were conducted between June 2015-June 2017, and baited remote underwater video stations (BRUVS) (n = 50 video drops/reef) were deployed in nine reefs across the islands. The fate of elasmobranchs caught by artisanal fishers varied by island. Martinique reported the highest proportion of fishers keeping their catch for subsistence among the study locations. In Guadeloupe, fishers most frequently sold their catch, and Tobago fishers engaged in both subsistence fishing and sale. Fishers retained almost all animals caught and reported reduced catches of elasmobranch compared to when they started fishing. BRUVS revealed relatively low elasmobranch occurrence and a low Shannon diversity index compared to Caribbean nations with less fishing pressures on elasmobranchs. The present study highlights the need for improved data on, and monitoring of, artisanal fisheries.

Seasonal variability of phytoplankton community structure in a coastal station of the Argentine continental shelf based on a chemotaxonomic approach

2024-08-22T18:12:32+00:00

The composition, abundance and size structure of the phytoplankton community at a coastal time series station (38° 28' S-57° 41' W, EPEA, Argentina) was characterized by applying the chemotaxonomic approach. The seasonal variability of pigment diversity determined by high-performance liquid chromatography (HPLC, n = 171), nutrient concentration (n = 934), and temperature, salinity and degree of stratification of the water column was identified (n = 190 CTD profiles). The CHEMTAX program was used to estimate phytoplankton abundance in terms of contribution to chlorophyll a concentration of the different phytoplankton pigmentary types (PPTs). Two different pigment indices were compared to estimate phytoplankton community size fractions throughout the year, giving contrasting results. Water column was mostly mixed, with minimum temperatures between July and September and maximum between January-March (range: 8-23 °C). Nitrate was the limiting nutrient, with minimal concentrations at the end of summer. It’s range varied between 0.010-13.330 μM, while silicate ranged between 0.016-10.670 μM without major seasonal variations, and phosphate between 0.120-2.180 μM. Fucoxanthin, chlorophyll c2, 19’-hexanoyl-oxy-fucoxanthin, diadinoxanthin, chlorophyll b, chlorophyll c3, peridinin and, alloxanthin, were the most frequent phytoplankton pigments. The PPT DINO-1 (dinoflagellates with peridinin), haptophytes types: HAPTO-6, HAPTO-7 and HAPTO-P showed a seasonal cycle with peaks of abundance in autumn and spring, while the diatoms DIATO-1 was high during the whole year and DIATO-2 mainly during winter. A pigment profile of a group of prymnesiophytes possessing MVChl_c3 was described. It was evident that at this site PPTs having potentially toxic species bloom under different hydrological conditions. DINO-1 is likely to bloom in April (autumn), with temperatures close to 18 °C and weak stratification conditions, while October bloom (spring) occurs with lower temperatures of 10-12 °C. DINO-4 was noted during January and February (summer), when temperature was > 18 °C, salinity < 33.7, and the water column showed maximum stratification. In contrast, the maximum abundances of DIATO-2 occurred between August and September (winter), under completely mixed conditions, high nitrate concentration and low temperature of 10 °C. This work constitutes the first description of the variability of the abundance of the main PPTs in a coastal a time series station in the southwestern Atlantic Ocean shelf throughout the annual cycle, demonstrating the power of chemotaxonomy and CHEMTAX to perform descriptive analysis of a large number of samples.

Reproductive biology of fringescale sardinella (Sardinella fimbriata Valenciennes, 1847) from Malampaya Sound, Palawan, Philippines

2024-10-28T16:19:37+00:00

Reproduction is a fundamental biological process that is essential for the continuous survival of fish species. Understanding their early life history and reproductive biology can explain how the population behave over time. A total of 1,238 fish samples were examined to determine the reproductive patterns and period of fringescale sardinella (Sardinella fimbriata) from Malampaya Sound, Palawan, Philippines. Monthly sampling from April 2023 to March 2024 revealed a 1:1 sex ratio. Gonadal examination of the fish revealed the presence of spawning individuals throughout the study period. The minimum size of matured fish observed was 11.0 cm and 11.1 cm for male and female S. fimbriata, respectively. The peak of spawning was April as indicated by the highest calculated GSI of 7.62% and fecundity of 18,465. A smaller peak was again observed in the month of September. The length at maturity was estimated to be 11.4 and 8.8 cm for males and females, respectively. Fecundity ranged between 2,700 to 36,067 eggs per spawn for size class between 11.1-14.8 cm and weight 13.07-31.93 g. Regression analysis between fecundity and morphometric characteristics such as body length, weight, eviscerated weight, and gonad weight revealed a positive correlation. Very low coefficients of determination were computed, ranging between 0.0028-0.1233. A significant association between fecundity and the morphometric variable gonadal weight was observed, as shown by the p-value of 0.0000. These outcomes are valuable data in the formulation of conservation and management strategies for the area. Implementation of appropriate conservation measures, monitoring of environmental parameters, strict enforcement of fishery regulation, coupled with increased environmental awareness and community participation will guarantee the long-term sustainability of the fringescale sardinella population and the preservation and sustainable use of marine biodiversity in Malampaya Sound.

Growth, mortality, exploitation, and recruitment patterns of Labeobarbus altianalis (Boulenger, 1900) in River Kuja-Migori, Kenya

2024-11-01T18:59:27+00:00

The Ripon barbel, Labeobarbus altianalis, a riverine fish found in the Lake Victoria Basin is regarded as species of less concern, but it is vulnerable to overfishing and population decline. This study aimed at determining growth, mortality, exploitation rate, and recruitment patterns of L. altianalis (Boulenger, 1900) in River Kuja-Migori. A total of 1,217 specimens with overall total lengths ranging from 9.5-41.5 cm (mean 28.5 ± 2.7) were collected monthly from January to December 2021. The fish were caught using an electrofisher in wadable areas and monofilament nets in deeper areas. Electronic length frequency analysis (ELEFAN) software in Fish Stock Assessment Tools (FiSAT II) program was used to analyze data. Natural mortality (M) Fishing mortality (F) and total mortality (Z) coefficients were 0.15 year^-1, 0.52 year^-1 and 0.67 year^-1 respectively. The asymptotic length (L_∞) was 44.94 cm TL while the instantaneous growth rate (K) was 0.15 year^-1. The exploitation rate was 0.44 year^-1 and the length-based growth performance index (Ø’) was 3.03. Results indicated that the longevity of L. altianalis was 9 years. Recruitment occurs throughout the year with bimodal annual recruitment peaks coinciding with the two rainy seasons in the region. This study provides important information for developing management advice for the L. altianalis riverine fishery.

First record of ornate ghost pipefish Solenostomus paradoxus from mainland India

2024-08-15T11:35:04+00:00

This study documents the first occurrence of a female ornate ghost pipefish, Solenostomus paradoxus (Pallas, 1770) from mainland India, collected at a depth of 40 m in the Arabian Sea. It provides the first detailed description of morphometric and meristic characteristics of this species from this region. Due to their small size, effective camouflage, and specific habitat needs, ornate ghost pipefish are challenging to study, and their solitary, seasonal behaviors further complicate research. This work adds valuable knowledge to the limited understanding of this elusive species and highlights the need for further exploration of underrepresented marine biodiversity.

Areal expansion of the box jellyfish Carybdea marsupialis (Linnaeus, 1758) towards the Ionian coasts of the Basilicata region (Italy)

2024-09-26T18:33:10+00:00

The study documents the presence of the box jellyfish Carybdea marsupialis in the waters of the Ionian Sea in Italy, which constitutes important data for the knowledge of new areal distribution of this species along the coasts of the Mediterranean basin. Carybdea marsupialis belongs to the phylum Cnidaria, class Cubozoa, and is known for its stinging and potentially dangerous stings for humans, making it a species of significant ecological and health interest. The species has previously been observed in other areas of the western Mediterranean, but the report in the Ionian Sea represents an eastward expansion of its distribution range. Results suggest that climate change, influenced by global warming processes and anthropogenic activities, facilitated the expansion of this species into the rest of the Mediterranean Sea. The work highlights the importance of continuous monitoring of indigenous and non-indigenous species and calls for international cooperation to manage any ecological impacts linked to the spread of these marine species.

Two new records of sea anemones (Cnidaria, Anthozoa, Actiniaria) from the Eastern Pacific coast of El Salvador

2024-10-14T15:50:41+00:00

Two species of the genus Actinostella Duchassaing, 1850 are documented for the first time on the coasts of El Salvador: A. bradleyi (Verrill, 1869) and A. californica (McMurrich, 1893). Both species are briefly described, and images of live specimens showing their main external features are provided, as well as images of histological sections showing some taxonomic characteristics of their internal anatomy. These two species are distinguished from each other primarily by the number of tentacles, the number of mesentery pairs, the arrangement of gametogenic tissue, and some differences in their cnidom. The record of these two species in El Salvador increases the number of sea anemones recorded for the country to 12. Additionally, an updated list of sea anemone species documented in El Salvador is provided.