Iranian Journal of Fisheries Sciences
Volume:23 Issue: 6, Nov 2024

This study aimed to identify the similarities in the catches of both experimental and commercial fishing efforts along the coast of Greater Accra, Ghana using trawls. Data for fisheries-independent (experimental, INFD) and fisheries-dependent (commercial, FID) catches were sourced monthly from June 2018 to May 2019. The obtained data was analyzed for non-metric multidimensional scaling (nMDS), diversity indices, similarity percentage, and cluster analysis using PRIMER 6 and PERMANOVA+ software. Sixty-seven fish species were obtained from both experimental and commercial catches. Species richness and Shannon-Weaver index (H’) showed no significant difference between INFD and FID catches. SIMPER analysis revealed a high dissimilarity percentage (64.95%) between commercial and experimental catches, with Selene dorsalis, Brachydeuterus auritus, and Galeoides decadactylus contributing the most. The nMDS and cluster analyses showed two distinct groups which indicated that not all grounds are used as fishing grounds by fishermen. Based on the findings, certain areas within the experimental fishing sites should be designated as marine protected areas to safeguard the populations of marine fisheries resources in Ghana.

This study collected 27 Blenniid specimens of 10 species from intertidal and subtidal habitats in the Persian Gulf and Oman Sea. The specimens were preserved and taxonomically identified before the genomic DNA extraction. The COI marker was then amplified and sequenced. Additional sequences from related subfamilies were obtained from GenBank. Phylogenetic reconstruction was carried out using Bayesian and phenetic methods. The study aimed to evaluate the phylogenetic position of the newly studied specimens and reconstruct the phylogenetic relationships among representatives of the Blenniidae. The amplification of the COI marker for Istiblennius edentulus and Salarias fasciatus in Iran is a significant advancement in understanding phylogeny, genetic diversity, and evolutionary connections in the area. A phylogenetic analysis was conducted using molecular data from this study and previous research from the southern waters of Iran. The study revealed that the subfamilies Blenniinae and Salariinae are paraphyletic and two tribes, Parablenniini and Omobranchini, form monophyletic groups. Istiblennius is considered a paraphyletic genus. Omobranchus mekranensis and O. punctatus are in a closer relationship than O. fasciolatus, which is grouped at a further distance. The phylogenetic tree places Ecsenius in a monophyletic clade at the furthest distance from other taxa, suggesting it may warrant a separate tribe rather than a genus.

Commercial production of microalgae is often more costly, as it requires significant quantities of various nutrients. This study aimed to utilize response surface methodology (RSM) to identify optimum levels of particular variables in a general economic culture medium, in the presence of sodium bicarbonate as an inorganic carbon source for increasing biomass productivity (BP) and total chlorophyll (CHL) content in Chlorella vulgaris microalgae. The different levels of independent variables were based on related references and studies. The predicted amount of biomass productivity and chlorophyll content in RSM was 119.37 mg/L/d and 7.61 mg/L, respectively, at optimized conditions: temperature 25°C, nitrate 716.39 mg/L, phosphate 14 mg/L, and sodium bicarbonate 259 mg/L. The results of the predicted and the actual response differed with R2: 0.75 and 0.81, and adjusted R2: 0.51 and 0.64 for BP and CHL, respectively, and were found to be in reasonable agreement with the better reliability model. This method is applied to the optimization of actual BP and CHL experiments and is found to outperform the existing methods. The optimal value found by the proposed method has a high prediction accuracy (less than 10% error), and it can be confirmed that the increased BP and CHL amount is significant (p<0.05). This information is particularly interesting for semi-industrial-scale processes, since the reduction and optimization of medium compounds might represent an improvement in the cost-effectiveness of the process and, eventually, greater profit.

Information about the reproductive biology of the silver barb is essential for conservation and domestication purposes. This study aims to analyze the reproductive biology of the silver barb in Lake Tempe, South Sulawesi, Indonesia. The aspects of reproductive biology analyzed include length-weight structure, sex ratio, length-weight relationship, condition factor, first gonadal maturity size (L50), gonadal maturity, and fecundity. This study used primary data, with silver barb fish being caught using gill nets every week from January to July 2023. The total length of the fish was measured using an ichthyometer with an accuracy of 0.1 cm, and the weight was measured using a digital scale with an accuracy of 0.01 g. The gonads were preserved in a 4% formalin solution, and fecundity was calculated using the gravimetric method. The length structure of male ranged from 8.9 to 22.9 cm, and females ranged from 8.9 to 28.5 cm. Males had weights between 21.2 and 183.2 g, and females 21.2 and 312.8 g. The overall sex ratio of males to females was 1:1, while the sex ratio during spawning was 1:3 (polygamy). The length-weight relationship for males and females was W = 0.0234L2.7349 and W = 0.0172L2.8766, respectively. The condition factor for both males and females was 1.02. The first gonadal maturity size for females was 18.3 cm and 19.9 cm for males. Spawning was partial, with fecundity ranging from 253 to 13,398 eggs.

The objective of this study was to evaluate the effects of predicted climate changes on primary production and vulnerability of fish species in coastal waters of the northern Persian Gulf. Remote sensing data including chlorophyll a and sea surface temperature (SST) through using MODIS sensor images of the Terra satellite were obtained from the Google Earth Engine system. Net primary production per day was estimated through the VGPM model from the NASA Oceanographic Database (2000-2022). To predict climate change in The LARS-WG microscale model that is compared and evaluated under three scenarios RCP2.6, RCP4.5, and RCP8.5 during 2020-2080. These scenarios predict an increase in the average annual temperature rise of 2.4 to 5.3°C for the future of the region. It showed the inverse correlation between SST and chlorophyll a, and a direct correlation between primary production rate and marine trophic index. The annual comparison of total commercial fisheries catches shows that fish catch will decrease by 169, 185, and 386 kg in the RCP 2.6, 4.5, and 8.5 scenarios, respectively. Correlation of the target species from the total catch with primary production shows that demersal fish species such as Pomadasys kaakan, Glaucostegus granulatus, Otolithes ruber, Atule mate and large pelagic such as Planiliza subviridis, Auxis thazard, Tenualosa ilisha, Thunnus tonggol and small pelagic such as Liza klunzingeri species and also jellyfish group express a positive relationship which is an indication of increased vulnerability to climate changes compared to other fish species.

Strombus canarium or dog conch is an economically important gastropod species for food in many coastal communities in the Philippines. Therefore, there is a need for protective measures to safeguard the stock in the wild. A better understanding of reproductive characteristics is needed to establish a management strategy for the conch fisheries. This study aims to determine the sex ratio, gonadosomatic indices, spawning period, and the relationship between shell length, lip thickness, and gonadal development stage of S. canarium. A total of 212 individuals were collected, of which 71 were male and 141 female. The overall ratio of the population is 1:1.99, of which females dominate in all sampling months. The male dog conch spawned from August to November, with a clear peak in September and October, while the female population has no clear peak. Only three gonadal developmental stages (intermediate, active, and ripe) were observed in both sexes across all sampling months. The correlation analysis indicated that the shell length and lip thickness were reliable indices of sexual maturity for both male and female S. canarium. The information gathered in this study indicates that this species exhibited partial spawning behavior, with complete spawning recorded only in males during specific periods. For fishery management measures, only sexually mature S. canarium with 76 mm shell length should be collected to ensure the individual can reproduce before being harvested.

The escalating issue of marine plastic pollution is primarily attributed to the extensive utilization of plastics coupled with their improper disposal in oceans. Microplastics (MPs), particles measuring less than 5 mm, result from the degradation processes of larger plastics, exacerbating ocean pollution. In this research, 100 samples of a carnivorous fish, Alepes vari, from the Chennai coast of Bengal Bay were collected and analyzed for the presence of MPs, which revealed varied accumulation ratios of MPs within their gastrointestinal tract. Through hydrogen peroxide digestion of 100 fish specimens, it was found that approximately 68% contained MPs, with an average abundance of 9.5 (±0.3) particles per individual. The predominant types of MPs observed were pellets (81.34%) and films (18.66%) with brown pellets comprising the majority (25.97%). Further analysis indicated a higher concentration of MPs in the stomach compared to the intestine. Fourier transform infrared radiation analysis- attenuated total reflection confirmed the presence of Polystyrene polymer in the ingested MPs, suggesting a potential link between the dietary habits of these fish and their ingestion of microplastics.

Microplastics (MPs) have become a significant environmental concern globally, with their pervasive presence in various ecosystems posing threats to marine life and human health. This study investigates the MPs contamination in a gastropod species Nerita albicilla found commonly along the Karachi coast. A total of 60 individuals of N. albicilla, 5 specimens from each site monthly were handpicked from the intertidal area of Hawksbay and Buleiji rocky shore from November 2022- April 2023. The shells were noted for morphometrics and visceral tissues were digested in 10% KOH solution in a ratio of 3∶1. Each digested suspension was filtered using 0.45 µm organic filter paper and observed with the help of a compound microscope. A total of 64 MPs (1.4±0.244- 3.6±0.678 item ind.−1) were recorded from 30 N. albicilla specimens collected from Hawksbay and 59 MPs (1.4±0.4 - 3±0.632 item ind.−1) from Buleji. The most dominant MPs types were microfibers, which made up to 84% and 88 % of total MPs at Hawksaby and Buleji, respectively whereas the most of MPs ranged in size range of 0-25 µm indicating anthropogenic pollution sources such as textiles, fishing gears, and synthetic materials commonly found in marine environments. The study underscores the ecological significance of gastropods in monitoring marine pollution and highlights the urgent need for mitigation measures to safeguard coastal ecosystems.

We studied the size dimensions and microchemical structure of the saccular otoliths (sagittae) of two populations of the annular seabream (Diplodus annularis) collected from the Djerba and Kerkennah Islands in Tunisian waters. The goals of our study included (1) measuring the otolith’s length (Lo), width (Wo), surface area (Ao), and perimeter (Po), and evaluating differences in these characteristics and microchemical elements between individuals of D. annularis within each Island, (2) exploring how potential fluctuating asymmetry (FA) in the otolith size affects the stock structure of D. annularis in two Islands, and (3) using these findings to recognize if there were distinct stock structures and connectivity between fish within the two Islands, to develop better-guiding policies for managing and governing the fishery within these Islands. The results revealed significant asymmetry in all size dimensions between the left and right otoliths among males and females within the Djerba and Kerkennah Islands and males and females between the two Islands due to FA. In addition, significant differences in otolith contents of K, Cs, and Pb were found between individuals of the two Islands. The significant asymmetry in otolith size dimensions among males and females of the two Islands due to FA and the noticeable difference in otolith microchemical elements between individuals of the two groups were attributed to some factors, such as fish age, environmental conditions, and fish biological traits. Therefore, the results confirmed the discriminant stock structure and limited connectivity between fish within the two Islands, which should be managed separately.

Regarding the exploitation of blue swimming crab (Portunus pelagicus) resources in the Java Sea in the last decade, it is presumed to be overfished. This study aims to analyze population dynamics by examining the relationship between carapace width and weight, recruitment patterns, the carapace width at first capture (CWc), growth parameters, mortality rate, and the exploitation level of P. pelagicus. The study was conducted in the north coastal waters of Jepara Regency, Indonesia, from May to September 2022 and February to August 2023. A survey method and direct observations were used to sample the catch area. The growth and mortality rate parameters were estimated from carapace width frequency data and analyzed using ELEFAN I software in the FiSAT II program package. The results showed that the relationship between carapace width and weight was positively allometric, following the equation W = 0.000053 × CW3.05. The carapace width at first capture (CWc) was estimated to be 110.5 mm. Peak recruitment occurred in August–September. The infinite carapace width (CW∞) was estimated at 189 mm, with a growth curve index of 1.6. The crab followed the von Bertalanffy growth function (VBGF) of CWt=189 (1-e (-1.6(t + 0.0584)). The total mortality was estimated at 4.46 yr-1, fishing mortality at 3.03 yr-1, and natural mortality at 1.43 yr-1. The exploitation rate (E) was 0.68. This indicates that the rate of exploitation of P. pelagicus has exceeded the maximum sustainable yield (E=0.5) and is overexploited.