Harvested Fish Research Articles

Seasonal Variation in the Nutritional Composition of Fishes in Tuticorin, Southeast Coast of India

Background: The nutritional quality of fish is very important for human consumers. The consumption of fish provides important nutrients to a large number of people worldwide and makes a very significant contribution to nutrition. The purpose of the study was to investigate the proximate composition of economically important marine water fish.
 Methods: The present work was conducted between March 2016 and February 2017, investigated the seasonal variations in the contents of protein, lipid, carbohydrate, ash and moisture in six fish species namely Sardinella fimbriata, Stolephorus commersonnii, Epinephelus areolatus, Carangoides chrysophrys, Gazza achlamys and Parupeneus indicus. The fish samples were collected from the fish market of Tuticorin. The proximate compositions of the samples were analysed according to standard AOAC methods.
 Results: Remarkable seasonal variations are found in the levels of the parameters studied in the six selected species. In all the seasons, Epinephelus areolatus is characterized by the highest moisture and ash contents, and Carangoides chrysophrys by the highest protein and carbohydrate contents, whereas Sardinella fimbriata contains more lipids. Except for moisture content all other nutrient compositions are high during the monsoon and post-monsoon periods. During summer the nutrient contents decrease due to breeding activities involving maturation of gonads, and after the breeding season the nutrient contents again show a rising trend. The seasonal variations in nutrient composition in fish are related to the cycle of maturation and depletion of gonads. Different phases of maturation are associated with marked quantitative fluctuations of each nutrient in different fishes.
 Conclusion: Based on the current finding, it is concluded that fishes are very good sources of protein, carbohydrates, ash, and lipids and that the biochemical constituents of the body tissues of fishes fluctuate during different seasons. The results suggested that the consumption of those fish species contributed to human health. Finally, this research work might help to understand the changes in nutritional values of some commercial fishes in various seasons and will assist in identifying the proper fish harvesting period.

Timing of hydrologic anomalies direct impacts on migration traits in a flood pulse fishery system

Abstract Understanding adaptive reservoir management strategies that balance ecological outcomes with other objectives necessitates properly articulated environmental objectives. Aside from flood pulse extent related metrics, residual‐based descriptors provide robust descriptions of fish assemblage structure and harvest. We proposed a model framework based on spectral analysis of hydrologic variation and the Multivariate AutoRegressive State Space (MARSS) model to statistically quantify the effect sizes of hydrologic variation impacts on total fish catch and functional group (migration types) fish harvest and applied it to 17 years of fish harvest data from the Lower Mekong River Basin (LMB). Our findings suggest that duration and timing of hydrologic anomalies matter as much as their magnitude. Anomaly droughts coupled with strong pulse can benefit species if timed correctly. Longitudinal migrators were more sensitive to anomalous floods and droughts than other migratory species. Fish catch projections using effect sizes derived from historical data revealed that a well‐timed and protracted drought followed by a powerful flood pulse would be advantageous to the fishery, but a flood delay could negate such benefits. Synthesis and applications: We designed a spectral analysis framework to quantify hydrological variation and linked it with fishery harvest records. Quantified effect sizes of hydrologic anomalous events demonstrated one designed hydrograph for fishery benefits: properly timed prolong drought followed by a strong flood pulse. Our results add to a growing body of research that suggests ecological flows can be engineered. For most dams, the rule curve describing reservoir releases and resulting downstream hydrograph are designed in an ecological vacuum in which the objectives are to maximize human services—power production, flood control or navigation. Our work demonstrates that hydrograph can be designed to manage aspects of functional biodiversity directly. Though the exact shape of our hydrograph may not apply to other engineered river systems, we suggest that the approach can be applied generally, and globally both to developed and developing river basins. Specifically, a functional biodiversity rule curve could be optimized as an additional objective function in a multi‐objective optimization framework. Our methodology provides a quantitative method for deriving an ecological flow for this larger tradeoff analysis.

A predator-prey model for the optimal control of fish harvesting through the imposition of a tax

This paper is devoted to the study of ecosystem based fisheries management. The model represents the interaction between prey and predator population with Holling II functional response consisting of different carrying capacities and constant intrinsic growth rates. We have considered the continuous harvesting of predator only. It is observed that if the intrinsic growth rate of predator population crosses a certain critical value, the system enters into Hopf bifurcation. Our observations indicate that tax, the management object in fisheries system play huge impacts on this system. The optimal harvesting policy is disposed by imposing a tax per unit of predator biomass. The optimal harvest strategy is determined using Pontryagin's maximum principle, which is subject to state equations and control limitations. The implications of tax are also examined. We have derived different bifurcations and global stability of the system. Finally, numerical simulations are used to back up the analytical results.

Perspectives on Rent Generation and Rent Appropriation in Fisheries

The article debates the origin of rent in natural-resource based industries (NRBIs) such as fisheries, and how the rent generated can be appro­priated. The Norwegian fish harvest­ing industry is used to illustrate the arguments. It is argued that the industry-specific institu­tional framework of the fish harvesting industry positively affects the compe­titive forces of the industry, and thereby its economic performance. Fishery management institu­tions create high barriers to entry for outside firms, and they dampen internal rivalry between incumbent firms. As a result, the opportunity to earn what this paper labels institutional rent arises. The article further argues that nature itself and how it is managed through, for example, harvesting rules, enables an NRBI to earn resource rent if the players get free or cheap access to the input factor, in this case fish. Finally, the article argues that it is stakeholders other than the harvesting companies that control both the institutional and resource rents, that is, the owners of the natural resource and the authorities who manage it as well as the industry-specific institu­tional framework. Nevertheless, neither the owners nor the authorities benefit from the industry-specific rent generated. The rent is appropriated by the capital owners and the crew onboard the boats in the form of above-normal profits and above-normal wages. Whether or not such a skewed rent distribution is considered fair and sustainable is a political issue.

How vulnerable are Wular Lake fishing communities compared to non‐fishing communities in rural Kashmir? Insights and interventions for development

AbstractWular Lake, one of the largest wetlands in Asia (13,000 ha in Kashmir Valley) is a biodiversity‐rich Ramsar site supporting nearly 32,000 rural people involved in harvesting fish, water chestnuts, lotus stems and fodder. With 2914 active fishers, Wular Lake contributes 54% of Kashmir's total fish catch. Large‐scale land‐use changes and global warming have resulted in siltation, reduced lake area and alterations in the water flow regime, threatening lake ecology and human livelihoods. A novel census‐based multi‐criteria Socio‐Economic Vulnerability Index (SEVI) was used to assess the vulnerability status of 23 fishing and 115 non‐fishing adjacent villages. All the fishing villages exhibited ‘low’ (0.21–0.40) vulnerability levels, except Kunas village (0.42). Interestingly, no significant differences could be found in vulnerability levels between fishing (23) and non‐fishing (115) villages, although the former exhibited relatively higher social sensitivity. A graphical decision matrix based on sensitivity and adaptive capacity scores provided a snapshot of vulnerability status for each village. Using SEVI scores, drivers (i.e., key indicators responsible for high sensitivity & low adaptive capacity) were identified and corresponding village‐specific development interventions are suggested with Kunas as an illustrative case village. Improving education levels, strengthening community and rural infrastructure, and expanding livelihood options were key short‐term strategies for improving resilience in Kashmir's Wular region.

Organochlorine pesticide residues in water, sediments and Nile tilapia (Oreochromis niloticus) of Lake Nakuru, Kenya and implications for its fishery

AbstractThe present study was conducted to assess the levels of selected organochlorine pesticide (OCP) residues in water, sediments and Nile tilapia, as well as the potential health risks to humans who consume the fish of Lake Nakuru. Nine composite water and nine sediment samples, as well as 30 fish specimens, were collected from five representative sampling sites within Lake Nakuru. The OCPs targeted in the present study included p,p′‐Dichlorodiphenyl dichloroethane (p,p′‐DDD), p,p′‐dichlorodiphenyldichloroethylene (p,p′‐DDE), p,p′‐dichlorodiphenyltrichloroethane (p,p′‐DDT), heptachlor, heptachlor epoxide, α endosulfan (1), β endosulfan (2), endosulfan sulphate, endrin, lindane, aldrin, dieldrin, methoxychlor and hexachlorocyclohexanes (alpha; beta; gamma; delta). Except for aldrin, all 16 OCPs targeted in the present study were detected. The OCP residue levels ranged from below detection limit (BDL) to 7.44 ± 0.66 μg/L, BDL to 6.39 ± 1.10 μg/kg ww and BDL to 319.74 ± 66.94 μg/kg ww in water, sediment and fish samples respectively. Some OCP concentrations exhibited significant differences across the sampling sites (p < .05). The residue level of endosulfan was above the European Union standard, whereas the target hazard quotient of heptachlor epoxide was above 1, therefore being unsafe for human consumption. The present study results indicate that most of organochlorine pesticides though banned in Kenya are still detected in the environment, posing potential long‐term health hazards to humans. Accordingly, environmental monitoring programme and mitigation strategies of reducing pollutant inputs into the lake is recommended, as well as an immediate ban on harvesting and consumption of fish from Lake Nakuru.

Dynamics of a harvested cyanobacteria-fish model with modified Holling type Ⅳ functional response.

In this paper, considering the aggregation effect and Allee effect of cyanobacteria populations and the harvesting of both cyanobacteria and fish by human beings, a new cyanobacteria-fish model with two harvesting terms and a modified Holling type Ⅳ functional response function is proposed. The main purpose of this paper is to further elucidate the influence of harvesting terms on the dynamic behavior of a cyanobacteria-fish model. Critical conditions for the existence and stability of several interior equilibria are given. The economic equilibria and the maximum sustainable total yield problem are also studied. The model exhibits several bifurcations, such as transcritical bifurcation, saddle-node bifurcation, Hopf bifurcation and Bogdanov-Takens bifurcation. It is concluded from a biological perspective that the survival mode of cyanobacteria and fish can be determined by the harvesting terms. Finally, concrete examples of our model are given through numerical simulations to verify and enrich the theoretical results.

Traditional knowledge, beliefs and practices on collection of lake flies (chaoborus and chironomus sp.) and their implications on food security

Lake Flies are edible insects with the potential of contributing to food security in that they are an alternative protein and micronutrient food source in freshwater lake regions. The main challenge in exploiting the lake flies is the difficulty in the collection. This study was conducted to identify sustainable traditional collection practices and forecasting techniques of lake flies and was implemented in Rusinga and Mfangano Island in Kenya. The ethnographic study employed multiple methods of data collection: focus group discussion (FGD), observations, and interview schedules. 5 (3 female and 2 male) key informants were selected for interview schedules aged above 60 years. 48 (19 female and 29 male) participants took part in FGDs they were divided into 8 sets each containing 6 participants and an age range between 18 to 40 years. Open data kit (ODK) software was used for data collection while analysis was conducted via thematic analysis framework using Nvivo version 10 software. Questions were administered on traditional lake-flies emergence forecasting, collection techniques, and devices. The emergence of lake flies is determined by moon sightings, the presence of strong winds, and the rainy season. Lake flies can be collected: in mid-air flight mode, in bushes along the shore, and during night operations using a light source (bulb, touch). Lake flies are collected using traditional tools: a woven basket with a stick handle, pots, a plastic basin, and a woven basket with a stick attached. Cultural myths associated with lake flies included: marriage partner/business customers’ attraction. Uses include libido enhancement, remedy for sickness, and good fish harvest indicator. In conclusion, lake flies have the potential to contribute to food and nutrition security as affordable and locally available alternative protein and micronutrient sources.

Current status and chronological development of fisheries and aquaculture in Bangladesh

While many parts of the world face water scarcity, Bangladesh is fortunate to have an abundance of the resource. The economic health of the country depends heavily on the fishing industry. Both capture fisheries and culture fisheries are common types of fisheries. Unlike culture fisheries, which is farming aquatic organisms in closed waters under controlled conditions, capture fisheries typically means harvesting fish and other aquatic organisms from open waters. This article examines Bangladesh's fisheries and aquaculture sectors using data from the Bangladesh Department of Fisheries and a few other relevant organizations and articles. Bangladesh is one of the world's major fish producers, with a total output of 4.62 million metric tons (MT) in the fiscal year 2020-2021. The majority (57.10%) of the country's fish and shrimp come from aquaculture, while 28.16 and 14.74 percent come from inland capture and marine capture, respectively. Bangladesh ranks only fifth in aquaculture production and third in inland open-water capture production whereas it stands first in hilsa production in the world. One of the most productive fish species is the major carp. There has been a modest increase in the country's inland aquaculture output over the past few decades, but the country also gets fish from inland capture and marine fisheries. The most recent ten years have seen significant contributions to inland capture fisheries and inland aquaculture from floodplains and ponds, respectively. The most common fisheries exports are frozen raw shrimp in blocks, individually quick frozen (IQF) shrimp and white fish, chilled and frozen Hilsa, crab, etc. In 2020-21, the country has earned BDT 4088.96 crore, or 1.24% of total export revenues, from exporting 76.59 metric tons of fish, shrimp, and other fishery products. However, over the past decade, the value of exported fish and fishery products has shown a nearly erratic trend. In contrast, annual production of the national fish hilsa has increased on a rising trend over the past decade. The number of carp seeds produced from both natural and artificial sources has followed an erratic increasing trend with some deviations during the past decennium. As the country's fisheries and aquaculture industries continue to grow, many cutting-edge technologies are making significant contributions that are helping to improve the quality of life for all involved. This has helped Bangladesh's economy expand over the past decade, particularly in fishing and aquaculture sectors.

An assessment of the state of the fish fauna in the lower course of rivers and floodplain water bodies in Lake Ilmen catchment based on the data from surveys with fine-mesh fishing gear in 2020–2021

Having analyzed fry seine catches from the lower reaches of the rivers flowing into Lake Ilmen and from floodplain lakes in the Msta and Lovat river deltas, we have updated information on the composition of the fish population of reservoirs and watercourses of the Lake Ilmen catchment. In total, 19 fish species belonging to six families were present in the catches in 2020–2021. The fish communities of the lower reaches of the rivers Volkhov, Lovat, Shelon, Veronda and floodplain lakes of the Lovat and Msta deltas featured high similarity, with the predominance of limnophilic species, in contrast to the riffle sections of the Msta, where rheophilic fish species dominated in abundance. At most survey sites, the catches were dominated by the main harvestable fish species of Lake Ilmen. The biomass of fish underyearlings in the autumn period of 2020 in floodplain lakes of the Lovat and Msta deltas was four to six times that of in the littoral zone of Lake Ilmen and comparable to the levels at survey sites in the lower reaches of the rivers Msta and Volkhov. Fry seining of river and lake areas within the Novgorod Region revealed fish species not previously reported for the Lake Ilmen catchment or formerly considered rare in the catchment. Lake Ilmen catchment being hydrologically isolated from the main invasion pathways as well as the absence of intentional acclimatization activities are factors promoting the stability of the native composition of the fish fauna and the reason why only one naturally dispersing species, the silver carp, has become naturalized in Lake Ilmen.

More and diverse contributions from aquaculture

Aquaculture is literarily and traditionally recognised as a collection of “farming finfish, shellfish and aquatic plants,” or as “the raising of water animals such as fish for food, or the growing of plants in water for food” (https://dictionary.cambridge.org/dictionary/english/aquaculture). In some agencies, aquaculture has been defined as the “breeding, rearing, and harvesting of fish, shellfish, algae, and other organisms in all types of water environments” (https://oceanservice.noaa.gov/facts/aquaculture.html/), although in some occasions, mariculture is used to indicate specifically aquaculture activities in marine and estuary environment. In general, aquaculture has been considered as a food production sector in our society, and over the last few decades, aquaculture has indeed been the fastest-growing sector of food production across the world.1 In addition to its significant contributions to the production of food, protein source, delicious food selection, and also to rural development, aquaculture activities have increasingly been used for conservation purposes including species and biodiversity conservation, habitat restoration and ecosystem service.1 In this issue, a group of scientists published an article, analysing the diversification of aquaculture activities through the investigation of literature, and then the definitions and roles of aquaculture were defined from an environmental and ecological point of view.1 Notably, “commercial aquaculture” should refer to the literal and traditional explanation of aquaculture, and is probably the main aspect of the aquaculture industry. The contribution of aquaculture in species conservation or habitat protection should be termed “conservation aquaculture,” and this kind of aquaculture has contributed significantly to the conservation of endangered species of fish, for example, the Kootenai white river sturgeon Acipenser transmontanus, and also two other species of sturgeons, the Chinese sturgeon A. sinensis, the Yangtze or Dabry's sturgeon A. dabryanus, in Changjiang (Yangtze) River, the latter two of which are now only relied on artificial reproduction to maintain the population or the species (Prof Jianbo Chang in Wuhan University, Personal Communication). Two other definitions of aquaculture in this article1 are restorative aquaculture and regenerative aquaculture, and it should be desirable and important to see more contributions of aquaculture in aquatic ecosystem service in future. It may not be believable if one says luxury products can be produced in aquaculture. In fact, pearls have an enduring attractiveness for jewellery, and freshwater pearl culture can be dated back to more than 2000 years ago in China, although its modern freshwater pearl culture has only a history of less than a century.2 Marine pearl culture is also a profitable and historical aquaculture activity with a global importance in countries or regions such as in China, Japan, some south-eastern Asian countries, some European countries, and Latin America. In this issue, Saucedo et al.3 summarised briefly the history of marine pearl culture along the Pacific and Caribbean coasts of many Latin American countries, outlined the current marine pearl aquaculture techniques and activities in these countries, and proposed an economically profitable and environmentally friendly pathway and strategies to reestablish Latin America as a major pearl producing region,3 which will provide a much more diversified selection of variously coloured and lustrous pearl ornaments. Also in this issue, a review article was devoted to the analysis of carotenoid production through the culture of microalgae, and the possible biotechnological approaches to improve the production of various carotenoids in different species of algae using either organic or inorganic nutrients were highlighted in this article.4 It is considered that a wide range of biomedically important bioactive compounds synthesised in algae can be produced through the culture of microalgae. It is apparent that aquaculture will continue to provide food and protein, but the roles and activities of aquaculture have become diversified with the production of a wide range of products, and simultaneously with significant value in nature conservation.

The productivity phenomenon of tilapia floating net cages in Jatiluhur Reservoir in line with the Citarum Harum program

The research was conducted to determine the productivity conditions of tilapia cultivation in the field along with the implementation of reducing the number of floating net cages. Production observations of tilapia culture were carried out on net cages owned by fish farmer in the Jatiluhur Reservoir from 2012 to 2019. The first period-P1 (2013-2015) was before the reduction in the number of net cages, the culture used a double net system and hybrid system. The second period-P2 (2016-2019) when the program started, KJA culture was carried out with a self-maintenance system (100% feeding for tilapia). The value of fish harvest weight ranged from 96.39-102.47 g (P1) and 196.84-278.33 g (P2). The range of survival rate is between 56.99–78.79% (P1), and 60.92–80.41% (P2). The feed efficiency value obtained in the P2 period was 75.77–86.34% while for P1 it was not defined because it was not a 100% feed system (independent). The daily weight gain, productivity and multiple values were as follows: 0.58-1.0 g/day, 0.14-0.45 g/m2, and 2.35-4.56x (P1); 1.43–3.00 g/day, 1.92–2.89 kg/m2 and 6.77–10.80x (P2). The monitored water quality parameters were still within a tolerable range for tilapia floating net cage culture.

SISTEM INFORMASI MANAJEMEN EVENT UNTUK PENINGKATAN PRODUKTIVITAS BUDIDAYA IKAN BERBASIS WEBSITE PADA DINAS PERIKANAN DAN KELAUTAN KABUPATEN INDRAMAYU

Fish farming is one of the sources of income for the people of Indramayu district which is currently widely occupied, it is not surprising that nowadays many people are flocking to cultivate fish. There are groups that cultivate including freshwater fish such as catfish, carp, and tilapia. There are also brackish water fish such as vaname shrimp, tiger shrimp, and milkfish. The fish cultivators in selling their harvests are still done conventionally, namely with the services of middlemen or collectors. This results in prices being often manipulated by collectors. One way to improve the sales system is to build an event management application in the field of fish harvest auctions. This application can be used as an alternative for cultivators for media promotion and cutting the marketing distribution chain. The benefits of this event management application are that cultivators get more competitive prices and can directly increase profits, while the benefits for buyers get cheaper prices. This web-based application, to provide information about an event or harvest auction that is managed online. This application is designed through the creation of flowcharts, UML, ERD, and mockups. Then it is implemented using the PHP programming language with the Laravel framework and the MySQL database management system

DYNAMICS OF A FISHERY MODEL WITH CONTINUOUS THRESHOLD HARVESTING POLICY AND ITS LEVERAGE FOR CONSERVATION AND MANAGEMENT

There is a global decline in marine fish abundance due to unsustainable harvesting. An effective harvesting policy can protect the overfished population from possible extinction. In this study, we used a mathematical model characterized by density-dependent refuge protection for herbivorous fish, exhibiting an anti-predator response in presence of a generalist invasive fish. The anti-predator behavior entails predator density-dependent reduced fecundity of the herbivorous fish. The model assumes a continuous threshold harvesting policy (CTHP) for the herbivorous fish and uses the catch-per-unit-effort (CPUE) hypothesis for harvesting the invasive fish. The CTHP allows harvesting of the herbivorous fish only when the density of the herbivorous fish exceeds a specified threshold value, thus ensuring the long-term sustainability of the herbivorous fish stock. The existence and stability of steady-state solutions and the bifurcations of the model are investigated. Our study reveals that the level of apprehension of the herbivorous fish and fishing efforts will play a significant role in the stability of the system. We examine the existence of the bionomic equilibrium and then study the dynamic optimization of the harvesting policy by employing Pontryagin’s maximum principle. We discuss different subsidies and tax policies for the effective management of a sustainable fishery. We use numerical simulations to compare the revenues corresponding to the harvest policies based on maximum sustainable yield (MSY), maximum economic yield (MEY), and optimal sustainable yield (OSY) for inferring an ecologically sustainable and economically viable harvesting policy.

Combining electronic tag data and fish harvesters’ knowledge to identify ocean management concerns

Understanding the distribution and reproductive behavior of marine species can inform ocean spatial management to address conservation needs and reduce risks of conflicts among various marine and coastal industries. Combining spatial data on species behavior with fish harvesters’ knowledge can be particularly effective for identifying spatiotemporal overlaps between human activities and critical events at various life stages of marine species. In the present study, the migratory behavior of Atlantic halibut (Hippoglossus hippoglossus), a flatfish of great economic importance in the Gulf of St. Lawrence, was characterized using electronic tags, and potential ocean industry impacts to the halibut population were identified using fish harvesters’ knowledge reported at public meetings and during semi-structured interviews. Results from electronic tagging analyses, including potential seasonal migration paths and presumed spawning locations, were presented to halibut harvesters who responded by identifying industries that could impact the halibut population. Harvesters identified the potential for halibut bycatch in the developing redfish trawl fishery as the main risk to the current high halibut abundance levels, which they attributed to the reduction of Gulf trawling and halibut bycatch since the 1990s. Other potential impacts to halibut identified by harvesters included offshore oil and gas drilling, and effluent discharge from a paper mill transformation project. The present study demonstrates that utilizing complementary data from both fish tracking devices and fish harvesters’ knowledge can help identify and anticipate potential conflicts between fisheries and other ocean industries, and ultimately inform the ecosystem-based marine spatial management of large marine ecosystems.

Maritime search and rescue in canada and the use of emergency radio beacons

Successful and early distress communication at sea is critically important for improving the survivability of marine accidents. A wide range of communication methods is available for seafarers to make distress calls. In particular, emergency radio beacons (i.e. emergency position indicating radio beacons (EPIRBs) and personal locator beacons (PLBs)) provide a reliable, commercially available means by which distress notification and incident location can be provided, particularly if time is not available to establish communication by radio or telephone. Given the importance of these devices, the International Maritime Organization (IMO) provides guidance for flag states to incorporate radio distress beacons within legal and search and rescue (SAR) frameworks. National regulations in Canada stipulate additional performance requirements for radio frequency transmission, operation and use. The governance structure for emergency radio beacons in Canada is comprehensive and complex, and worldwide accident statistics show that when EPIRBs and PLBs are used, the rescue rate increases. Still, in Canada, a significant proportion of maritime activities (e.g., fish harvesting) do not require the use of these devices, and it is in these sectors where the greatest number of fatalities is occurring. Our paper explores the governance structure for the development and use of EPIRBs and PLBs in Canada, identifying where challenges and gaps exist and considering ways to close these gaps. Discussion is provided on the flexibility and adaptability of the governance system to incorporating new information and changes in technology.

A fish harvesting model with Allee effect and Holling type II functional response

Fish harvesting is one of the most profitable investments as it does not require financial costs other than fishing equipment. Therefore, population harvesting models have become attractive to many researchers in the field of mathematical bio-economics. With so many models of fish harvesting, few of them discuss the use of Holling type II functional response to model the interaction between fish populations, harvest effort, and the conditions that are necessary to sustain fish harvesting in the long term. In this paper, we first present a differential equations model describing the dynamics of the fishes population under the presence of harvesting activity. We assume that, in the absence of harvesting activities, the growth dynamics of the fishes population is governed by a logistic growth with Allee effect. The harvesting term is represented by Holling type II functional response. The existence conditions for positive equilibrium point are derived, and the stability of the model equilibrium points are analyzed. An explicit fitted numerical method that is much faster than the Matlab's ODE solvers is developed to solve the model. Finally, numerical simulations are used to confirm the theoretical results.

Levels of Escherichia coli as Bio-Indicator of Contamination of Fish Food and Antibiotic Resistance Pattern Along the Value Chain in Northwest Ethiopia

Microbiological contamination in fish origin foods is the leading risk for public health. Among the range of pathogenic bacterial species that cause fish food borne diseases is Escherichia coli. The pathogenic strains of Escherichia coli cause diarrhea by producing and releasing toxins and can also be the cause of food spoilage in fish. A cross-sectional study was conducted to assess hygienic practices of fish handlers, to evaluate bacterial load and antimicrobial resistance patterns of Escherichia coli along the fish value chain in Northwest Ethiopia. Systematic and purposive sampling techniques were used for uncooked and cooked fish samples respectively. From a total of 180 fish samples, 36 (20%) were positive for Escherichia coli. From 115 uncooked and 65 cooked fish samples examined, 27 (23.5%) and 9 (13.8%) had E. coli respectively. The highest mean bacterial count was observed in raw fish samples (6.13 × 105 cfu/g), followed by cooked fish samples (2.81 × 104 cfu/g). Among the interviewed fish handlers, 83.3%, 76.7% and 80% of respondents had good knowledge and attitude towards using a clean cutting-and-filleting board, storing raw and cooked foods separately and using an apron for reducing the risk of fish contamination, respectively. All 36 isolates were 100% sensitive to ciprofloxacin and gentamycin. Of the Escherichia coli isolates subjected to tetracycline, 55.6% were resistant, 8.3% were intermediate and 36.1% were susceptible. This study revealed that there was a lack hygienic practice and high Escherichia coli profiles were observed. Hence, it could be wise to advise the fish harvesters, fish traders, hotels and restaurants about fish food safety practices from harvesting to consumption to improve fish food safety practices and quality standards of fish harvested and sold in northwest Ethiopia.

Implications of COVID-19 on oxbow lake (Baors) Fisher's community, Bangladesh: resilience to food security against probable natural calamities

The purpose of studying the consequence of COVID-19 on oxbow lake (Baor) fisher's community is to counteract the negative impacts on livelihoods with food security and figure out diversified resilience options for sustaining basic needs of life. Individual questionnaire interviews, oral history, focus group discussion, and telephonic interviews were among the methodological techniques used to gather primary data. The Baor fisher's community was impaired with income, food and feeding habit, health and marketing. The Baor fishers had to stop harvesting or reducing the amount of fish harvest because of gradual decreasing of consumer demand and prices of fish during the course of COVID-19 pandemic period. The transportation costs were raised up to 50%–80%, while the prices of fish decreased by 15%–30% prior to the onset of COVID-19 pandemic. The frequency of fish consumption was significantly come down to 37.5%. Many households substituted fish to farm reared hens, eggs, domestic hens and ducks, lentils, and vegetables during the period of lockdown across the country. Supply chains of fish and fish culture inputswere disrupted due to inadequacy of transportation facilities. Many school- and college-going students were dropped outduring the ongoing pandemic situation due to their financial problems (10%) and early marriage (7.5%). The secondary sources of income (labor of netting in other aquaculture farms) of Baor fisher's community were also impaired. The resilience options of this study will be helpful to minimize the sudden economic crises, ensure dynamic fish value chains and food security, protect individuals from ongoing health hazards, and promote sustainable food production systems followed by social cohesion and stabilityagainst the prevailing challenges owing to the pandemic and other natural calamities.

Histopathology unveiling the structural damage in gonads of Catla catla due to freshwater contamination

Potentially harmful materials, e.g., heavy metals, pesticides, dyes, and hydrocarbons, are often released untreated into freshwater bodies. When such pollutants are released in large quantities, there may be large-scale, sudden mortalities of aquatic organisms. This study summarizes experimental evidence about the disruption of gonadal development due to freshwater contamination. Adult fish specimens of Catla catla were collected from the River Chenab downstream of the Chakbandi Main Drain (CMD) entrance into the Chenab River. CMD collects domestic and industrial sewage wastes from Faisalabad city and disposes them into River Chenab, polluting this water body. Water samples were analyzed from each site of fish harvest for water quality parameters. Collected fish specimens were subjected to histopathological evaluation to detect the impact of pollution on the gonads of this fish species. The male Catla catla gonads showed marked histopathological alterations such as testes degeneration, generalized tissue degeneration produced by fragmentation and detachment of basement membrane, necrosis, and fibrosis in the testis. A loss of tubular arrangement, rupturing of the blood vessels, delimiting seminiferous lobules, vascular hypertrophy of the interstitial compartment, and appearance of a clustered organization were observed. The follicular epithelium in vitellogenic oocytes, rupturing and detachment of follicular basement membrane tissue with cytoplasmic vacuolization, immature oocytes with scattered yolk droplets, hypertrophied follicular epithelium, interstitial proteinaceous fluid deposition, and structural deterioration of follicles with early oocytes were observed in the ovary.