Water Fish Species Research Articles

Risk assessment of toxic residues among some freshwater and marine water fish species.

Egypt has several beaches, as well as the Nile River and a few lakes; therefore, it could compensate for the lack of protein in red meat with fish. Fish, however, may become a source of heavy metal exposure in humans. The current study was to assess the level of five toxic metals, lead (Pb), cadmium (Cd), mercury (Hg), arsenic (As), and aluminum (Al), in six species, namely, Oreochromis niloticus (O. niloticus), Mugil cephalus (M. cephalus), Lates niloticus (L. niloticus), Plectropomus leopardus (P. leopardus), Epinephelus tauvina (E. tauvina), and Lethrinus nebulosus (L. nebulosus), collected from the El-Obour fish market in Egypt. The residual concentrations of the tested toxic metals in the examined O. niloticus, M. cephalus, L. niloticus, E. tauvina, P. leopardus, and L. nebulosus species were found to be higher than the European Commission's maximum permissible limits (MPL) for Pb and Cd by 10 and 20%, 15 and 65%, 75 and 15%, 20 and 65%, 15 and 40%, and 25 and 5%. In contrast, 30% of L. niloticus exceeded the MPL for Hg. It was shown that the average estimated daily intake (EDI) and the target hazard quotient (THQ) in fish samples are below safety levels for human consumption and hazard index (HI < 1). From the human health point of view, this study showed that there was no possible health risk to people due to the intake of any studied species under the current consumption rate in the country.

Human Health Risk Assessment of Trace Metals in Water, Sediments and Edible Fish Species Collected from Idu-Uruan Beach, Akwa Ibom State, Nigeria

Human Health Risk Assessment of Trace Metals in Water, Sediments and Edible Fish Species Collected from Idu-Uruan Beach, Akwa Ibom State, Nigeria

Changes to fish assemblage following the selective removal of black bullhead (Ameiurus melas)

Abstract Black bullhead is among the most abundant and successful non‐native fish species in European fresh waters. A number of studies have indicated that its physical removal might be a potential solution to minimize possible adverse impacts; however, so far there have been no field studies to confirm this. This study quantified the population dynamics of both native and non‐native fishes in a small slow‐running lowland river within the Ponjavica Nature Park in Serbia before and after the black bullhead removal with fyke nets. The removal of black bullhead resulted in statistically significant changes in the abundance of two native species – an increase in rudd (Scardinius erythrophthalmus) (by 5.3 times) and a decline in bleak (Alburnus alburnus) (by 2.3 times). A significant increase was observed in three non‐native fish species – the abundances of topmouth gudgeon (Pseudorasbora parva), pumpkinseed (Lepomis gibbosus) and Prussian carp (Carassius gibelio) increased 25.5, 4.9 and 4.2 times, respectively. There were also substantial changes in the diversity of the fish assemblage after the black bullhead removal, illustrated by changes in diversity indices: Shannon's index doubled, while the Simpson's dominance index decreased threefold. The catch‐per‐unit‐effort and the biomass‐per‐unit‐effort values indicated the dominance of the black bullhead in the fish assemblage during the mass removal phase of the study. The young‐of‐the‐year/adult ratio did not vary in relation to abundance, which confirmed that black bullhead might not compensate for fishing mortality with increased recruitment. The results suggest that black bullhead plays a significant role in structuring the fish assemblage and that its removal may have both positive and negative effects on species abundance and diversity. These findings can contribute to the conservation of native fish species and improvement of future management programmes.

Threatened fish species in the Northeast Atlantic are functionally rare

AbstractAimThe criteria used to define the International Union for Conservation of Nature (IUCN) Red List categories are essentially based on demographic parameters at the species level, but they do not integrate species' traits or their roles in ecosystems. Consequently, current IUCN‐based protection measures may not be sufficient to conserve ecosystem functioning and services. Some species may have a singular combination of traits associated with unique functions. Such functionally distinct species are increasingly recognized as a key facet of biodiversity since they are, by definition, functionally irreplaceable. The aim of this study is to investigate whether threatened species are also functionally rare and to identify which traits determine extinction risk.LocationEuropean continental shelf seas.Time period1984–2020.Major taxa studiedMarine fish.MethodsUsing newly compiled trait information of 425 marine fish species in European waters, and more than 30 years of scientific bottom trawl surveys, we estimated the functional distinctiveness, restrictedness and scarcity of each species and cross‐referenced it with their IUCN conservation status.ResultsIn European continental shelf seas, 38% of the species threatened with extinction (9 out of 24 species) were identified as the most functionally distinct. By mapping extinction risk in the multidimensional species trait space, we showed that species with the greatest risk of extinction are long‐lived and of high trophic level. We also identified that the most functionally distinct species are sparsely distributed (4% of the total area on average) and have scarce abundances (&lt;1% of the relative mean abundance of common species).Main ConclusionsBecause a substantial proportion of threatened species are functionally distinct and thus may play unique roles in ecosystem functioning, we stress that species traits—especially functional rarity—should become an indispensable step in the development of conservation management plans.

Nutritional composition of three commercially important brackish water fish species recorded from Batticaloa Lagoon, Sri Lanka

Fish is a high-quality animal-source food in the nourishment of millions worldwide. The most edible part of the fish is the muscle and which provides a proper balance of proximate and non-proximate nutrition and has a relatively low caloric value than other meats. The present study aimed to fill the gaps in the nutritional profile of three brackish water fishes (<em>Arius maculatus</em>, <em>Mugil cephalus </em>and <em>Oreochromis niloticus</em>) sourced from Batticaloa Lagoon, Sri Lanka. The study was conducted from November 2019 to February 2020 and fish were sampled from Kallady, Kattankudy and Arayampathy fish markets. The nutritional compositions such as moisture content, protein content, fat content and ash content of epaxial muscles of selected fishes were analyzed with standard methods. The moisture content was high among the fish muscles ranging from 56.73 ± 5.96% to 81.48 ± 2.52%. The protein content of A. <em>maculatus</em>, M. <em>cephalus </em>and O. <em>niloticus </em>muscles ranged as 15.36 ± 1.62%, 17.33 ± 1.96% and 13.7 ± 1.55% respectively. Amidst the selected fishes, O<em>. niloticus </em>is a lean fish (1.27 ± 0.35%) while A<em>. maculatus </em>(3.20 ± 0.59%) and M<em>. cephalus </em>(2.43 ± 0.37%) are low-fat fishes based on the muscle lipid content. The ash content of A. <em>maculatus</em>, M. <em>cephalus </em>and O. <em>niloticus </em>ranged from 1.22 ± 0.15% to 1.77 ± 0.45%, respectively. All the measured proximate parameters were significantly different (<em>P</em>-value &lt; 0.05%) among the three fish species. The results of this study revealed that the A. <em>maculatus </em>contains the highest value of lipid and ash content while O. <em>niloticus </em>contains higher amount of moisture content. The M. <em>cephalus </em>can considered as a good source of animal protein compared to the other two fish species.

Changes in Climate Factors and Catches of Fisheries in the Republic of Korea over the Three Decades

We investigated the changes of main climate factors and their relationships with the catches of offshore fisheries of the Republic of Korea over the past 30 years (1981 to 2010), using a trend analysis and Pearson’s correlation analysis. This study focused on seven fish species that have been preferred in Korean cuisine for centuries. Not only the air temperature, but also the sea surface temperature (SST) on the coast of Korea has risen (p &lt; 0.05) in the period. The rise in SST over 30 years is significantly correlated with the rise in temperature (p &lt; 0.01), but not with precipitation. Over the past 30 years, catches of anchovies and squid have increased significantly, while Alaska/walleye pollock has become almost extinct (p &lt; 0.01). The analysis of this study indicates that cold water fish species have decreased or disappeared in Korean fisheries and have been replaced by warm water fish species. Our findings suggest that the fish species caught in Korean offshore fisheries have changed due to climate change, especially global warming. These results also suggest that there may be a threat to the food security of Koreans, so it is necessary to take measures to protect this food resource.

Fish Tissue Contamination with Organic Pollutants and Heavy Metals: Link between Land Use and Ecological Health

Under pressure from existing and emerging contaminants, lotic ecosystems are becoming increasingly susceptible to ecological deterioration. Therefore, investigations of the impacts of persistent organic pollutants (POPs) and heavy metals on riverine fish health, water quality, and biotic integrity are critical. We examined the effects of 52 POPs and heavy metals on ecological health and land use, based on the monitoring of fish assemblages and river water quality from 2007 to 2014. Among the 52 chemical species, 35 were present in water and fish tissues, including eight heavy metals. The concentrations of these POPs and heavy metals in 12 fish species are presented. Most POPs were either undetected or present at negligible levels in fish tissues, although a few polycyclic aromatic hydrocarbons (PAHs) and organochlorine pesticides (OCPs; dichlorodiphenyltrichloroethanes and heptachlor epoxide) were detected above the screening values (SVs). Hg, As, and Cd were detected in most water samples and fish species at concentrations above their SVs. Among the fish species in the investigated trophic guild, heavy metal contents were in the order of Zn &lt; Cr &lt; Cu &lt; Pb &lt; Se, while trophic levels were in the order of insectivorous &lt; omnivorous &lt; carnivorous. Agricultural cover showed an association with endosulfan II (R2 = 0.50, r = 0.70), followed by alachlor (R2 = 0.43, r = 0.66). For PAHs, all detected substances showed significant relationships with forest cover. Ecological health assessment revealed that most river sites are in poor condition, indicating the direct impacts of pollutants. In conclusion, of the 28 POPs detected, 16 PAHs and 3 OCPs (hexachlorobenzene, lindane, and heptachlor epoxide) were of significant concern, such that action is needed to curb their inflow to the riverine environment. The studied river basin is under substantial threat from harmful POPs that endanger ecological health and fish biodiversity.

Population dynamics and stock assessment of Red snapper (Lutjanus johnii) in the Bay of Bengal Bangladesh waters

Red snapper (Lutjanus johnii) is one of the most significant commercial fish species in the marine waters of Bangladesh. A comprehensive understanding of the biology and dynamics of fish is important for the effective management of the fishery. Therefore, it would be the first study on this highly valuable commercial species to draw stock status and assessment of reference points in the upper Bay of Bengal, Bangladesh using three different length-based methodological approaches which are TropFishR (Tropical Fisheries Analysis with R), LBSPR (Length-based Spawning Potential Ratio), LBI (Length based Indicators), and a catch-based method DB-SRA (Depletion-based Stock Reduction Analysis). An allometric growth pattern (b=2.66) was observed in the length-weight relationship of Red snapper. The VBGF (von Bertanlanffy Growth Function) life history parameters for Red snapper were L∞=99.33 cm, k=0.16 year−1, and based on LCCC (Length Converted Catch Curve) analysis, the total mortality (Z=0.59 year−1), natural mortality (M=0.24 year−1) and fishing mortality (F=0.35 year−1) were estimated. The results show that this fishery is currently likely to be overfished due to overexploitation and the stock’s spawning biomass (SPR=28%) is below the target reference point because most of the catch (72%) was found to have under the maturity level. This study recommended a length to catch between 51 and 62 cm and proposed a yearly landing limit of 175 mt as OFL (Over Fishing Limit) for the next ten years in line with the annual fishing ban to raise the stock’s biomass over the Bmsy level for maintaining sustainable yield of 271 mt as MSY.

Feeding habits of four-finger threadfin fish, Eleutheronema tetradactylum, and its diet interaction with co-existing fish species in the coastal waters of Thailand.

This study assessed the feeding habits of four-finger threadfin fish, Eleutheronema tetradactylum, and its diet relationship with other fish species in the tropics. Fish samples were collected from four locations along the coastal regions of Thailand. A whole year field sampling event was conducted to investigate the diet relationship of threadfin fish with other ten co-existing fish species in Pattani Bay during January 2021 and January 2022. E. tetradactylum was an active and specific predator with significant diet shift during ontogeny. Specifically, the juvenile fish fed largely on zooplankton especially Acetes/shrimp postlarvae, and small sized-fish fed on penaeid shrimps, while medium and large-sized fish shifted their diets to a combination of penaeid shrimp, fish and squid. Size and sex of fish as well as site of collection significantly affected gut fullness index and average number of food type (p<0.05). Transitional sex fish predated almost entirely on other fishes (87.2%), whereas male and female fish fed mainly on penaeid shrimp (66.5%) and other fish (51.3%), respectively. Fish size and mouth opening controlled the size of prey, with the larger fish with larger mouth-opening fed primarily on the larger size of prey. Moreover, E. tetradactylum shared its diets inclusively with Epinephelus coioides, Johnius belangerii, Scomberomorus commerson, Scomberoides lysan, Otolithes ruber and Lutjanus russelli. Penaeid shrimp and teleost fish were the main food types shared by these fishes. This study provided important information on the feeding habits of E. tetradactylum and its diet relationship with other co-existing fish species living in the same habitat of a tropical coastal region.

Perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) in water and edible fish species of Karun River, Ahvaz, Iran: spatial distribution, human health, and ecological risk assessment

ABSTRACT Per- and polyfluoroalkyl substances (PFASs) such as perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) are environmental contaminants with unfavorable impacts on human health and nature. This study aimed to determine the PFOA and PFOS concentration in water and fish samples from Karun, the largest river in Iran. According to the results, the PFOA and PFOS in water samples were 5.81–69.26 ng/L and not detected (n.d.)–35.12 ng/L, respectively. The dry season displayed higher concentrations in water samples than in the wet season. The maximum PFOS concentration measured was related to Barbus barbules sp. (27.89 ng/g). The human health risk assessment indicated minor risks (hazard ratio, HR < 1) from PFOA and PFOS through consuming contaminated drinking water and fish. Only HR value of PFOS in downstream area exceeded slightly 1.0, indicating potential health risk due to consumption of the river fish. Considering the average PFASs concentration, the risk quotients (RQs) showed low ecological risk.

Unveiling the power of environmental DNA: A review of eDNA application to monitoring threatened fish in Indonesian Waters

This study examines environmental DNA (eDNA) techniques to detect and monitor threatened fish species in Indonesian waters. By analyzing 17 selected documents out of 284 papers and 310 metadata files, the study identified 30 Indonesian threatened fish species through eDNA technology which only assessed 8.5% of 352 threatened fish species in Indonesian waters based on Fishbase data, particularly in families such as Osphronemidae, Melanotaeniidae, Dasyatidae, Carcharhinidae, and Gobiidae. The paper discusses estimating fish abundance using eDNA analysis, including sample collection, eDNA concentration analysis, correlation with fish biomass, and field application. Challenges and limitations in estimating fish abundance through eDNA are addressed, such as misinterpretation, environmental factors, eDNA persistence, and sampling bias. The findings highlighted the potential of eDNA as a valuable tool for detecting and monitoring threatened fish species in Indonesian waters. However, further research and conservation efforts are needed in this area. By addressing the identified challenges and limitations, a better understanding of threatened fish populations can be gained, leading to effective conservation strategies and the long-term survival of these species in Indonesian waters.

РЕЗУЛЬТАТЫ ИССЛЕДОВАНИЙ АЗОВСКИХ ПОПУЛЯЦИЙ ОСЕТРОВЫХ РЫБ ПРИ ОСУЩЕСТВЛЕНИИ МОНИТОРИНГА ПРОМЫСЛА СТАВНЫМИ ОРУДИЯМИ ЛОВА У КУБАНСКОГО ПОБЕРЕЖЬЯ

Introduction. After depletion of the Russian sturgeon Acipenser gueldenstaedtii Brandt &amp; Ratzeburg, 1833 and stellate sturgeon Acipenser stellatus Pallas, 1771 stocks at the end of the 20th century, their abundance in the Azov and Black Sea Basin has been maintained through the release of the juveniles obtained by the means of artificial reproduction. Resulting from the strengthening protection of the aquatic living resources and gradually increasing number of the released juveniles, since 2014, as evidenced by the research studies, an increase in the population abundance of these fish species and their biomass is observed in the Azov Sea (from 42 t in 2015 to 998 t in 2022). Unstable state of the sturgeon populations in the coastal waters of the Azov Sea predicated the relevance of this work. Its aim was to investigate the distribution and age–length composition of the populations of the sturgeon fish species in the coastal waters of the Azov Sea. Methods. This study was based on the data on age–length composition collected over the course of the investigation of sturgeon by-catches in stationary pound nets in the coastal waters of the Azov Sea within an administrative unit Primorsko-Akhtarsky District (Yasensk and Achuevo Spits). According to its results, out of all sturgeon species, in the autumn season, the stellate sturgeon prevailed—53 %; the share of Russian sturgeon was 43 %, and for beluga sturgeon, it was 4 %. In summer, the Russian sturgeon share in the catches was 79 %, and for stellate sturgeon, it was 21 %. There have also been recorded some differences of the Russian sturgeon and stellate sturgeon length composition between the early spring and middle autumn, which can result from the fact that the sturgeon individual of greater length leave their wintering sites in the Azov Sea open waters earlier and sooner enter the coastal waters in spring. Conclusions. This study makes it possible to improve the assessment of the stock status and distribution for the sturgeon fish species in the Azov Sea.

Water Quality Plays an Important Role in the Socio-Economic Condition of the Local Community: A Study on the Kushiara River

In Bangladesh around 7.5% of the fish is harvested from the rivers, being one of the main sources of fish in the country. The water quality of the river must be within standard values to maintain aquatic biodiversity. In this study, water quality, available spaces for fish, and socio-economic status of fishermen were analyzed to find their relationships in Kushiara River, Fenchuganj, Sylhet. Samples of water quality and fish species were collected from August 2017 to September 2021. At the same time, fishermen were surveyed to find out their economic status. The water quality analysis showed all the parameters analyzed (pH, Dissolved Oxygen (DO), Biochemical Oxygen Demand (BOD), Chemical Oxygen Demand (COD) and Total Dissolved Solid (TDS)) are within the range of international and Bangladesh standards for surface water. The pH, DO, BOD, COD, TDS was respectively 7.1-7.99, 5.5 mg/l to 8.4 mg/l, 1 to 4.6 mg/l, 17 to 32 mg/l, 30 to 70 mg/l. Where the local standard is 6.5-8.5, more than 5 mg/l, less than 6 mg/l, 17 to 32 mg/l for pH, DO and BOD. The international standard is less than 34.2 mg/l. and 30 to 70 mg/l for COD and TDS in that order. A total of 40 species of fish are recorded in 2017 and 49 in 2021. The average income of a local fisherman was 3 USD to 15 USD in the off pick season (December- February), and 7 USD to 30 USD in the peak season (September-November). The fish merchant’s daily income was 4 USD to 20 USD in the off-peak season and 7 USD to 30 USD in the peak season. So all fisher man, fish traders can spend their life by fish catching and fish trading. Due to fish production those people can earn money and can fulfill their daily needs. It is concluded that the water quality was adequate for fish diversity and to sustain the socioeconomic condition of the fishermen and fish traders in the Kushiara River.

Acanthocephalan and Trematode Endoparasites in Rabbitfish Siganus fuscescens from the Selected Coastal Areas of Surigao City, Surigao del Norte, Philippines

The rabbitfish, Siganus fuscescens, is an economically important fishery in Surigao City, Philippines. This study was conducted to assess the zoonotic potential of the endoparasites infecting S. fuscescens collected from September to November 2021 in the three selected coastal areas of Surigao City, Surigao del Norte, Philippines. Isolated worms were identified using light microscopy and appropriate staining techniques based on their morphological characteristics. Two endoparasite species were recovered from the intestine of the siganids, the acanthocephalan Sclerocollum rubrimaris, and the trematode Hexangium sigani. Single infections of S. rubrimaris were common among fish samples, and an overall prevalence of 45% and a mean intensity of 30±23.34 (N=150) were recorded. The fish length (rs= -0.243) and weight (rs= -0.139) had a significant but weak negative correlation with the parasite load. With prevalence of 100%, results revealed that the Canlanipa station has a significantly higher prevalence of infection (100%) compared to Perlas (14%) and Bilang-bilang (22%). The endoparasites are not zoonotic, yet, intestinal hemorrhage was observed in fish with heavy infections with S. rubrimaris. This study is the first report of endoparasite infection in siganids of Surigao. A survey of endoparasites in other fish species in the coastal waters concerning water quality and heavy metal pollution is recommended.

Evaluation of seagrass beds as a foraging and nursery habitat based on the structure of the fish community in Nusmapi Island, West Papua, Indonesia

Abstract. Manangkalangi E, Sembel L, Tebaiy S, Manuputty A, Rumayomi MR, Musyeri P, Sawaki D, Orissu D, Manumpil AW, Kaber Y. 2022. Evaluation of seagrass beds as a foraging and nursery habitat based on the structure of the fish community in Nusmapi Island, West Papua, Indonesia. Biodiversitas 23: 5539-5550. Seagrass beds are one of the ecosystems inhabited by various coastal aquatic fauna, including fish. However, information on the temporal role of this ecosystem for fish fauna, particularly diurnal and nocturnal, is still limited. Therefore, this study was conducted to describe daily variations in the fish species composition, their ecological index, developmental stages, and trophic groups in a seagrass bed on Nusmapi Isl., Manokwari. The species composition differed between day and night sampling periods based on the results obtained from 40 species of fish belonging to 21 families and 7 orders. Furthermore, fish species consisted of three trophic groups (omnivores, carnivores, and herbivores), with omnivores and carnivores dominating during the day and at night by 48.6% and 87.5%, respectively. Species found in seagrass beds majorly consisted of juvenile stage individuals (65.9%). Individual abundance varied from day to night and was mainly found among group-forming species, such as S. spinus, S. trilineata, S. punctatissimum, and M. pralinia. The index of diversity, evenness, and dominance at the two relatively similar sampling times described the overall stability of fish communities in seagrass beds. The results indicate that seagrass beds serve as foraging and nursery grounds for many fish species in coastal waters. In addition, the management and protection of fish biodiversity and coastal fishery resources are affected by the ecosystem function.

Environmental Factors Associated with Fish Diversity in Two Tributaries of River Chittar, Southern Western Ghats, Tamil Nadu, India

In the present research, we examined Ichthyofaunal diversity, habitat preferences, and environmental variables in the Chittar River tributaries in Tamilnadu, India. The species composition is comprised of 14 species representing 4 orders, 6 families, and 12 genera. Cyprinids were the most abundant group in the assemblage composition of fishes, which was approximately 61.5%-83.33%. According to the Shannon-diversity index of fish populations in the study streams, the upstream of New Falls and the Harihara river reveal a high species richness. Among the recorded fish species, Puntius arenatus, belonging to the family Cyprinidae, is in the vulnerable categories of the IUCN List. However, the fish species exhibited a higher density in the headwaters upstream and the density decreased in the downstream. However, bedrock and boulders were observed as the predominant substrates in upstreams (sites 1 and 3) throughout the seasons. The results of Principal Component analysis of water quality factors and fish abundance and species richness revealed that dissolved oxygen, total hardness, and alkalinity have less impact on fish abundance, whereas TDS and conductivity had a substantial correlation in all downstreams. Fish were influenced by a diverse natural and anthropogenic longitudinal pattern, as well as regional disturbances induced by adjacent land users.

The preliminary DNA barcoding dataset of fishes from Chinese coastal waters

DNA barcoding is a molecular method for species identification based on a short standardized DNA sequence derived from the 5’ region of the cytochrome c oxidase subunit I (COI) gene, which is widely applied in marine fish identification. In this study, DNA barcodes were generated for 1,671 specimens representing 309 morphological marine fish species belonging to 223 genera and covering 101 families from Chinese coastal waters. The mean Kimura 2-parameter (K2P) genetic distances within species, genera, families, and orders were 0.20%, 20.94%, 24.45%, and 25.34%, respectively. As expected, the mean interspecific distance was higher than the mean intraspecific distance. Phylogenetic trees based on Bayesian inference (BI) and neighbor-joining (NJ) methods agreed with the taxonomic classifications. A total of 306 operational taxonomic units (OTUs) were reidentified via automatic barcode gap discovery (ABGD) analysis. An estimated nucleotide substitution matrices showed a transversion bias compared to transitional mutation. The amino acid variations of the barcoding region were also examined, and 13 amino acid sites exhibited high variability. Overall, our findings confirmed that DNA barcoding is a highly reliable mean of identifying fish species in Chinese coastal waters, and that the barcode library established here would facilitate the monitoring and management of the marine fishery resources in China.

The impact of sugar alcohols and sucrose on the physical properties, long-term storage stability, and processability of fish gelatin gels

Fish gelatin is becoming a popular alternative to mammalian gelatins due to religious restrictions, cultural preferences, ecological, and ethical concerns. Warm water fish gelatins (WWFG), as opposed to gelatins from cold water fish species, have more similar physical properties, and hence represent an alternative, to mammalian gelatins albeit a lower sol/gel transition temperature and gel strength. In warm climates, WWFG gels may therefore exhibit reduced storage stability at temperatures above this transition temperature because of e.g., a more pronounced acid hydrolysis of the sol fraction. To improve the long-term storage stability of WWFG, gels were prepared with two different sugar alcohols, sorbitol and xylitol, and a non-reducing sugar, sucrose. The change in the sol/gel transition temperature, gelling and melting kinetics, and gel strength of the gels were analyzed using small amplitude oscillatory shear measurements. Short-term and long-term storage stability tests at ambient temperature, 30 °C and 40 °C indicated improved stability of gels with co-solutes without significant differences between the type of sugar alcohol or sucrose. The stability of the gels increased with increasing concentrations of sugar alcohols. The degree of hydrolysis of the gelatin in the gels were investigated using SEC-MALS analyses which supported the bulk rheology stability results. Using sucrose led to browning and high viscosity, which may pose challenges regarding the processability and industrial applications.

Some biological aspects of four marine fish species in Iraqi marine waters, northwest Arabian Gulf

The study described some biological characteristics of four commercially important fish species in Iraqi marine waters including Planiliza klunzengeri, P. subviridis, Acanthopagrus arabicus and Otolithes ruber from February 2020 to January 2021. The length and weight of individual fish caught were measured. The length-weight relationships were W= 0.027L2.715 for P. klunzengeri, W= 0.034L2.670 for P. subviridis, W= 0.030L2.867 for A. arabicus and W= 0.023L2.755 for O. ruber, and all species indicated negative allometric growth. The lower values of the relative condition factor (Kn) were found at the mid-lengths of P. klunzingeri and P. subviridis, and the large individuals for A. arabicus and O. ruber. Scales were used for age determination and measurements, and the back-calculated lengths-at-ages were calculated using the body proportional formula. Asymptotic total lengths (L∞) estimated were 29.6, 32.8, 44.9 and 70.6 cm for P. klunzengeri, P. subviridis, A. arabicus and O. ruber, respectively. These results could assist in fisheries management for the sustainable exploitation of these commercially important species in Iraqi marine waters.

Future changes in the seasonal habitat suitability for anchovy (Engraulis japonicus) in Korean waters projected by a maximum entropy model

Anchovy (Engraulis japonicus), a commercially and biologically important fish species in Korean waters, is a small pelagic fish sensitive to environmental change. Future changes in its distribution in Korean waters with significant environmental change remain poorly understood. In this study, we examined the projected changes in the seasonal anchovy habitat in Korean waters in the 2050s under three representative concentration pathways (RCPs; RCP 2.6, RCP 4.5, and RCP 8.5) by using a maximum entropy model (MaxEnt). The MaxEnt was constructed by anchovy presence points and five environmental variables (sea surface temperature, sea surface salinity, sea surface current speed, mixed layer depth, and chlorophyll-a concentration) from 2000–2015. Future changes in the anchovy habitat in Korean waters showed variation with seasonality: in the 2050s, during winter and spring, the anchovy habitat area is projected to increase by 19.4–38.4%, while in summer and fall, the habitat area is projected to decrease by up to 19.4% compared with the historical period (2000–2015) under the three different RCPs. A substantial decline (16.5–60.8%) is expected in summer in the East China Sea and the Yellow Sea—main spawning habitat. This considerable decrease in the spawning habitat may contribute to a decline in the anchovy biomass, relocation of the spawning area, and changes in the reproduction timing in Korean waters. Our findings suggest that seasonal variation of the anchovy habitat should be considered to ensure effective future management strategies for the effect of climate change on fisheries resources, particularly for environmentally sensitive species, such as anchovy.