Fishing Activities Research Articles

Linkage between spatiotemporal distribution of environmental DNA and phenological activity in an amphidromous fish, ayu Plecoglossus altivelis altivelis, in a river located in its northernmost distributional area.

Environmental DNA (eDNA) is a promising tool for the continuous monitoring of fish ecology and diversity. However, its potential for describing the phenological activity of fish has rarely been examined. This study aimed to elucidate a linkage between the spatiotemporal distribution of eDNA and the phenology of an amphidromous fish, ayu Plecoglossus altivelis altivelis, in a river in Hokkaido, Japan, which is its northernmost distributional area. A significant positive correlation between eDNA concentration and catch per unit effort of P. a. altivelis in the river confirmed the use of eDNA as a surrogate for the abundance of P. a. altivelis. eDNA of P. a. altivelis was first detected in late April on a sandy beach adjacent to the river mouth. Subsequent to its first detection at the lowest site in the river in early May, eDNA spread throughout the river, indicating the upstream migration of P. a. altivelis. Spawning activity was also represented by a rapid increase in eDNA concentration and its surge at night in the lowest reaches of the river during September and October. These results suggest that upstream migration and spawning primarily commenced when the water temperature reached 10°C and decreased below 20°C, respectively. This observation is consistent with the behavioral responses observed in P. a. altivelis populations from other regions of Japan. Consequently, this study demonstrated that eDNA distribution was closely linked to the phenological activity of P. a. altivelis and that eDNA is a powerful tool for studying the phenology of migratory fishes.

Impacts on population indices if scientific surveys are excluded from marine protected areas

Abstract Marine protected areas (MPAs) are increasingly common worldwide, typically restricting fishing activities. However, MPAs may also limit scientific surveys that impact benthic habitat. We combine a historical data degradation approach and simulation to investigate the effects on population indices of excluding surveys from MPAs. Our approach quantifies losses in precision, inter-annual accuracy, trend accuracy, and power to detect trends, as well as correlates of these effects. We apply this approach to a proposed MPA network off western Canada, examining 43 groundfish species observed by four surveys. Survey exclusion particularly impacted less precise indices, species well-represented in MPAs, and those whose density shifted in or out of MPAs. Redistributing survey effort outside MPAs consistently improved precision but not accuracy or trend detection—sometimes making estimates more precise about the ‘wrong’ index. While these changes may not qualitatively alter stock assessment for many species, in some cases, ∼30 percentage point reductions in power to detect simulated 50% population declines suggest meaningful impacts are possible. If survey restrictions continue expanding, index integrity could further degrade, eventually compromising the management of exploited populations. Regulating surveys within MPA boundaries therefore requires careful consideration to balance MPA objectives with the need for reliable monitoring.

Analysis of Climate Variable and Fisherman Perception on Climate Change Divers in Negombo Lagoon Area


 
 
 Climate change has undoubtedly become one of the most contentious issues in the international environmental debates and has escalated the impacts on fishery industries and fishing communities globally. This study was conducted to quantify the variations in climate variables, and coastal vegetation that may affect the fisheries industry due to climate change over past three decades in the Negombo lagoon area. Further, the knowledge and awareness of fisheries and associated communities on climate change was investigate. To understand the dynamics of the precipitation and temperature, monthly data for 30 years (1989-2022) were collected from the Department of Meteorology and 19 Module Bio-climatic Variables (MBV) were calculated to determine the climatologycal variation. The change in the coastal vegetation was analyzed using the Landsat 8 satellite using ArcGIS 10.8. A questionnaire survey and a focus group discussion were carried out as assess the knowledge, awareness and impact of climate change in the fisheries community (n=80). The mean annual and minimum and maximum precipitation ranged from 118.6 mm-268.6 and 0.6 mm - 826.6 mm. The mean, maximum, and minimum temperatures varied from 28.8o C- 32.3o C, 33o C-34o C and 29o C-30o C. Out of 19 MBV variables, 9 variables had increasing trends while 3 variables had decreasing trend. The change percentage of coastal vegetation cover from 1992-2002, 2002-2012, 2012-2022 was observed as 35.71%, 4.99% and 6.13%. As per the peoples‘ knowledge of climate change, it was highlighted that around 50% of respondents does not have a proper idea on what is climate change (40% of respondents stated that the variation of precipitation and wind is the climate change drivers; Further, 40% of respondents attested that land use change with time has accelerated climate change while 30% of respondents mentioned that lack of coastal awareness and restoration programs is the second main reason for accelerated climate change that affect the fishery industry). The outcomes of the focus group discussion revealed that fishing activities are heavily affected by climate change drivers, and some engage in alternative jobs in extreme climatic conditions to feed their families. Finally, fishery communities highlighted the need for the government and other responsible authorities to take necessary actions to adapt and strengthen the resilience to climate change. This study corroborates the timely and topical obligation for sustainable fisheries management action planning for the Negombo area.
 Keywords: Climate change, Coastal mangrove vegetation-precipitation-temperature change, Fisheries communities, Knowledge, Awareness, Negombo
 
 

Preliminary Study on Floral Distribution, Abundance and Diversity of Mangroves in Vankalai, North-west Coast of Sri Lanka

Sri Lanka harbors a remarkable amount of mangrove habitats. Northern Province shares about 16% of the total mangrove extent of the country. Vankalai consists of several ecosystems which range from arid-zone thorn scrubland, arid-zone pastures and maritime grasslands, sand dunes, mangroves, salt marshes, lagoons, tidal flats, sea-grass beds and shallow marine areas. Due to the integrated nature of shallow wetland and terrestrial coastal habitats, this sanctuary is highly productive, supporting high ecosystem and species diversity. The research was aimed to identify the distribution, abundance and diversity of mangroves in Vankalai of the Northern Province, Sri Lanka. Ten 25m wide belt transects with 10m intervals were randomly arranged in the small patch of mangrove vegetation perpendicular to the 350m of shoreline across the water-land gradient. Each transect was divided into five 5mx5m subplots for convenience of sampling. True mangrove species in each transect were identified and counted. The quantitative data has been used to compute the Shannon diversity index (H), Simpson Index (D) and Shannon Evenness (E), which were used to compare the diversity of the study sites. Ten different mangrove species including Avicennia marina (n=115), Avicennia officinalis (n=73), Rhizophora apiculate (n=33), Rhizophora mucronata (n=102), Sonneratia alba (n=3), Pemphis acidula (n=4), Excoecaria agallocha (n=40), Lumnitzera racemose (n=91), Bruguiera cylindrical (n=97), Ceriops tagal (n=31) were identified and they were belonging to five families; Avicenniaceae (n=2), Rhizophoraceae (n=5), Lythraceae (n=1), Euphorbiaceae (n=1) and Combretaceae (n=1). Further, based on the IUCN status, two mangrove species (Sonneratia alba and Bruguiera cylindrical) were identified as endangered species. The highest Shannon diversity index (H=2.21) and the lowest Simpson index value (D=0.14) were observed in the transects of point 1 due to minimal disturbances. The least Shannon diversity index and evenness were recorded in the point 5 as 1.65 and 0.85 respectively at the point 5 since fishing and tourism activities take place in the proximity of this place. The Shannon diversity index varied at the points of 1 (H=2.21)>2 (H=2.10)>3 (H=1.89)>4 (H=1.84)>5 (H=1.65) whereas Simpson index value were varied at the points of 1 (D=0.14)<2 (D=0.17)<3,4 (D=0.18)<5 (D=0.19) respectively. Pollution and human interaction would have degraded the environmental quality of the mangrove habitats. Based on the observations it was found that the extent of disturbances was minimum at the points of 1 and 2 whereas anthropogenic influence was increased at the points of 3<4<5 respectively. Further, use of mangrove poles and sticks to build fish baits and fishing rods by the anglers could possibly destroy these small patches of mangroves. Hence, actions should be taken for conservation of existing patch and replenishment of new mangroves. 
 Keywords: Mangroves, Diversity, Shannon Diversity Index (H), Simpson Index (D) and Shannon Evenness (E)

Quantification of the fishing effort of the artisanal fleet in the Maritime-Terrestrial National Park of the Atlantic Islands of Galicia in the absence of vessel monitoring system

The fishing effort in the marine area of the four archipelagos of the Maritime-Terrestrial National Park of the Atlantic Islands of Galicia (PNMTIAG) is estimated. In the absence of vessel monitoring systems (VMS), a stratified quantitative sampling programme of passive gears deployed and of vessels fishing, in the case of non-passive gears, was used. This programme allowed to quantify the fleet and the fishing effort of each gear, to identify the fishing areas, to obtain a list of the usual vessels in each archipelago and the characteristics of a standard vessel for each of them. The fishing fleet in the park was estimated between 283 and 317 (± 81.5) artisanal fishing vessels working at least once a year with a fishing effort density around 5–26 vessels/km². This effort density was higher than in different MPAs in the western Mediterranean area. However, the density of fishing effort in terms of gears/km² was comparable to some of these same MPAs since the fleet spreads its effort over other fishing areas. The creation of fishing restricted areas inside the National Park could lead to an increase in fishing effort in its waters. The vessels working in the archipelagos of Ons and Cíes are slightly larger than those in Sálvora and the latter larger than those in Cortegada. Around 427 crew members work in this fleet have been estimated considering only vessels using passive fishing gears. Also, these results showed that the methodology used may be sufficient but is not adequate to establish a systematic monitoring of all fishing activity. The implementation of VMS, although not compulsory for small-scale fishing vessels, is essential for the best possible management of fishing activity, especially in areas of special protection such as the one in this study.

Economic and Marketing Study of Purse Seine Catch Results in Bone Bay Waters, Bone Regency

Harvesting marine biological resources especially fish, is still largely dotted with fishing activities. One of the fishing businesses engaged in fishing that has already developed in Indonesia, especially in the South Sulawesi Bone Bay is a ring trawl business (Purse seine). The magnitude of the potential of fisheries in the bone bay led to the formation of a large number of purse seine fishing business units in Bone district. However, erratic natural conditions make production yields non-permanent so it is necessary to know how much this business is still feasible to continue. In this purse seine catch production flow, aspects of marketing and distribution anaises are an important part of knowing the effectiveness of production to support the economy of society. The research was conducted from October to November 2020. In this study the income received by the purse seine capture business unit in bone bay was 1,115,964,357.52/year and indicated that the purse seine business carried out by the fishing business actor was feasible to develop by the division between receipts and costs has a value of more than one (>1). Based on the Marketing aspect the value of marketing efficiency of purse seine catches is set according to the marketing channel value <1 which means it can be said that both channels are efficient marketing on each fish commodity.

First records of the sicklefin (Mobula tarapacana), bentfin (Mobula thurstoni), and spinetail (Mobula mobular) devil rays in the Chagos Archipelago.

Recent encounters with sicklefin (Mobula tarapacana) and bentfin (Mobula thurstoni) devil rays in the Chagos Archipelago provide the first confirmed observations of live specimens of these species in this region. Examination of illegal fishing photo archives collected during enforcement revealed these endangered species, and spinetail devil rays (Mobula mobular), are being caught within the archipelago's vast no-take marine protected area. Future cooperation between authorities and mobulid ray experts is crucial to improve the availability and accuracy of enforcement data and improve management of illegal fishing and mobulid ray conservation activities.

High replacement of soybean meal by different types of rapeseed meal is detrimental to rainbow trout (Oncorhynchus mykiss) growth, antioxidant capacity, non-specific immunity and Aeromonas hydrophila tolerance.

A 12-week feeding trial was conducted to evaluate the effects of replacing soybean meal with different types of rapeseed meal (RSM; Chinese 95-type (oil press model) rapeseed meal [C95RM], Chinese 200-type rapeseed meal [C200RM], cold pressed rapeseed cake [CPRC], Indian rapeseed meal [IRM] and Canadian rapeseed meal [CRM]) on growth, antioxidant capacity, non-specific immunity and Aeromonas hydrophila infection tolerance in 990 fingering (average weight 12.77 ± 0.01 g) rainbow trout (Oncorhynchus mykiss). A basal diet was prepared using fishmeal and soybean meal as the main protein sources, the other 10 diets were formulated with five types of RSM at 20% (C95RM20, C200RM20, CPRC20, IRM20, CRM20) or 35% (C95RM35, C200RM35, CPRC35, IRM35, CRM35) inclusion levels to replace iso-nitrogenous soybean meal. Regardless of the RSM source, dietary inclusion of 20% RSM significantly reduced the weight gain rate (WGR) and digestive enzymes activities (except C200RM20) of fish, but increased the blood urea nitrogen (BUN) and hepatic malondialdehyde (MDA) content (except CRM20). Fish fed with CPRC20 and IRM20 exhibited relatively higher plasma cortisol and MDA content, but lower content/activities of triiodothyronine (T3), thyroxine (T4) and glutathione peroxidase (GPx) in plasma, lysozyme (LZM) and complement 3 (C3) in serum, catalase (CAT) in liver, and respiratory burst activity (RBA) of head kidney macrophages. The intestinal and hepatic tissues fed with 20% RSM were damaged to some extent, with the CPRC20 and IRM20 groups being the most severely affected. Regardless of the RSM source, dietary inclusion of 35% RSM significantly decreased WGR and digestive enzymes activities, but significantly increased plasma BUN and MDA content. The fish fed with CPRC35 and IRM35 exhibited relatively higher plasma cortisol, MDA, serum triglyceride, BUN content, but lower content/activities of T3, T4, C3, and LZM in serum, CAT, peroxidase and GPx in plasma, CAT in liver, RBA and phagocytic activity of head kidney macrophage. The hepatic and intestinal tissues damage was the worst in the IRM35 group among the 35% RSM inclusion groups. These results indicate that including ≥20% RSM in the diet, regardless of the source, reduced the growth, antioxidant capacity, immunity, and survival to Aeromonas hydrophila infection in rainbow trout.

Women’s experiences of participatory small-scale fisheries monitoring in Timor-Leste

Participatory fisheries monitoring can create many benefits, such as increasing community engagement in marine management, generating data for data-poor fisheries, and empowerment of fishing communities. Although most participatory monitoring studies have focused on men monitoring their own fishing activities, evidence from studies examining women’s increased participation in broader fisheries management suggests that monitoring programmes should also incorporate gender-inclusive approaches. Furthermore, the data collectors’ perspectives regarding the effects that participating has on themselves or their community are often not included in reporting or evaluating monitoring processes and methodologies. Such gaps in participatory monitoring approaches may overlook different people’s participation and experiences of fisheries and their management, and so disregard the general consensus that community-based fisheries are deeply socially embedded. Using the participatory photography methodology, photovoice, this paper explores women’s participation in fisheries management, and how this links with various forms of empowerment, as represented by stories and images shared by the participants of a fisheries monitoring programme in Timor-Leste. Their resulting photo stories explore motivations for participating in the monitoring programme, the enabling or constraining conditions which influence participation, and the implications for broader marine management. The participants’ photo stories demonstrate the importance of relationships in creating an enabling environment for participatory processes, and how monitoring can be relationship-building, creating a positive feedback loop that leads to awareness-raising, empowerment, advocacy and collective action. This study contributes to the growing body of literature around participatory monitoring as an empowering process by amplifying the voices of women through unpacking their experiences and aspirations.

Real time AIS tracking system for fishermen using microcontroller-based approach

Fishing activities in the waters of Banyuwangi are relatively intense. Local fishermen often venture 50 nautical miles from the coastline using small boats. These boats are lacking adequate communication and navigation equipment, causing difficulties in obtaining assistance during emergencies. This study aims to develop an Automatic Identification System (AIS) device to be installed on fishing boats. The AIS device developed for this research incorporates the STM32F4 microcontroller, CMX7032 Evaluation Board, VHF Antenna, and Global Positioning System (GPS) as its main components. The integration and configuration of each component will be elaborated in this paper. Performance testing has yielded promising results, as the AIS device was capable of transmitting data up to 10 nautical miles from the Base Station. Utilization of AIS technology would enhance safety and communication among fishermen. Through careful integration and configuration of these components, the AIS device effectively ensures that the fishermen’s positions are accurately tracked and communicated. The successful development and testing of this device underscore its potential to bridge the communication gap, offering timely assistance and enhancing the overall safety of these seafarers.

Effects of extended dietary supplementation with Santalum album essential oil on hemato-biochemical changes, innate immune response, antioxidant status, and expression of related gene in Nile tilapia (Oreochromis niloticus).

The effects of long-term dietary supplementation with sandalwood (Santalum album L.) essential oil (SEO) was investigated on hemato-biochemical biomarkers, immune status, antioxidant capacity, and resistance against Staphylococcus aureus in Nile tilapia (Oreochromis niloticus). Five groups (with four replicates) of O. niloticus (12.60 ± 0.20 g) were fed diets supplemented with SEO at doses of 0, 0.5, 1.0, 2.0, and 4.0 mL/kg diet for 60 days. Results indicated a substantial increase in blood protein levels and lower serum cholesterol, cortisol, glucose, urea, creatinine levels and, transaminase activities of fish fed a 2.0-mL SEO/kg diet. Serum lysozyme activity, nitric oxide, complement-3 levels, and phagocytic activity were significantly improved in O. niloticus after 60 days of feeding SEO-supplemented diets. Dietary SEO at level of 2.0-mL SEO/kg diet increased the activities of SOD, CAT, and GPx, and decreased MDA levels in liver homogenate. In addition, dietary 2.0-mL SEO/kg diet significantly upregulated antioxidant genes expression (CAT, SOD, GPx, GST, and GSR) with downregulation of apoptotic genes (HSP70, TLR2, caspase-3, and PCNA) in the liver. Furthermore, SEO-enriched diets significantly down-regulated pro-inflammatory (TNF-α, IL-1β, and IL-8) and up-regulated anti-inflammatory cytokine genes (TFG-β and IL-10) in the spleen. Moreover, SEO fortification increased the relative percentage of survival against S. aureus challenge and regulated immune-antioxidant genes in the spleen after the challenge. Overall, the results revealed that long-term using SEO might strengthen the physiological performance, hepatic oxidant/antioxidant balance, innate immune response, and resistance of O. niloticus against bacterial infections.

Ecotourism: Another Benefit of Agro-Silvo-Fishery and Trigona Apiculture in Peatland Ecosystem of Baru Village, Banyuasin, South Sumatra

Agro-silvo-fishery and Trigona apiculture are two business models developed in the peatland ecosystem in Baru Village, Banyuasin District, South Sumatra. Since the beginning of 2022, two demo plots have been built in the same village landscape as part of the business model implementation. The system‘s agro-silvo-fishery was established by constructing a pond around a paddy field and planting betelnut, vegetables, and fruit trees. Local fish that had acclimated to the acidic peatland habitat were captured during the flooding and raised in the ponds. In the constrained biophysical and chemical conditions of swampy terrain, this method is thought to be the greatest way to provide a variety of revenue. Individual farmers cannot afford the costs associated with setting up this system, especially when it comes to constructing the pond and dykes. Individual farmers cannot afford the costs associated with establishing this system, especially when it comes to constructing the pond and dykes. Hence, support from the district and village government and program partners is valuable. The farmer group harvested corn and vegetables from the dykes and rice from the paddy fields in the first year, and fish were not ready for harvest. However, the local BUMDes saved the day by creating weekly regular fishing activities and competition events, generating revenue from tickets. Moreover, the Trigona apiculture became a popular place for those outside the village to learn free of charge. Based on profitability analysis, the NPV of establishing agro-silvo-fishery is Rp103.036.769 per 0.8 ha for 30 years, with additional income from ecotourism is estimated to reach Rp21.600.000 per year. The established demonstration plot has the potential to become an ecotourism destination, and the key is to maintain the surrounding flowers and plants as the source of food for bees and the water condition for the fish.

UTILIZAÇÃO DA BIODIVERSIDADE VEGETAL NO PESCAR E NO COLHER NO TERRITÓRIO DAS ÁGUAS DO BAIXO TOCANTINS, CAMETÁ-PA

This article discusses the use of plant biodiversity in two important activities that mark the ways of life of traditional populations. We sought to understand the ethnobiological knowledge in traditional communities used in the manufacture of fishing and extractive equipment. Hold discussions on fishing activities and plant extraction; and the variety of equipment are the specific objectives that guide this research. To collect the data, semi-structured interviews, field notebooks and open questionnaires were used for families living in four communities in the island region of the municipality of Cametá. Eight (08) devices made from ten (10) plant species were identified. The matapí was the equipment most mentioned by informants. Specific species are identified in (04) botanical families, with Arecaceae being the most cited family. The informants presented important ethnobiological knowledge about the species, as well as the ethnodefinition of each individual and their respective use in the community.

Ups and downs: An insight on the stranding pattern of Guiana dolphins, Sotalia guianensis, in the Amazon Estuary, Northern Brazil

Abstract Long‐term systematic records of cetacean strandings are valuable indicators of temporal responses of specific cetacean populations and communities to natural or anthropogenic pressures. They also help guide management objectives and conservation actions. Generalized additive models (GAMs) were used to analyse 10 years of systematic and opportunistic surveys of Guiana dolphin strandings in the Amazon Estuary region, Northern Brazil. The spatial distribution of strandings was assessed through kernel density maps, and age‐at‐death structure of this population was described. The model results revealed marked seasonality in the strandings and, by extension, the mortality of Guiana dolphins in the Amazon Estuary. This seasonality varied between the inner estuarine regions and Atlantic coastal area, reflecting the environment's characteristics. Long‐term decline of strandings in the Amazon Estuary inner region and unusual high mortality of young sexually mature individuals were detected. These results, besides the high stranding rate detected for the species, are mostly attributed to the species' interaction with intense fishing activity in the region. Conservation efforts should consider the seasonality of Guiana dolphin strandings in the Amazon Estuary. The systematic monitoring of strandings, especially in high‐frequency areas, is recommended for assessing long‐term species mortality. Additionally, implementing management actions related to the species' interaction with fishing activities, such as regulatory enhancements, gillnet modifications and seasonal no‐fishing zones, is advised. Educational campaigns targeting fishermen and riverine communities are essential to reduce bycatch and the folkloric use of the species. This study underscores the effectiveness of stranding data as a source of biological and ecological information, and as a tool for understanding human actions affecting coastal populations of aquatic mammals. It emphasizes the need for urgent studies to characterize this population, clarify the influence of bycatch as an anthropogenic pressure and implement effective conservation actions to preserve the Guiana dolphin population.

Satellite tagging confirms long distance movement and fast dispersal of Patagonian toothfish (Dissostichus eleginoides) in the Southwest Atlantic

IntroductionTo better understand Patagonian toothfish (Dissostichus eleginoides) movement and habitat in the Southwest Atlantic, fifty popup satellite archival tags (PSATs) were deployed off Davis Bank on North Scotia Ridge between 2019 and 2020 on individuals ranging from 97-139 cm total length.MethodsPSATs (18 Lotek Wireless PSATFLEX and 32 Wildlife Computers MiniPAT) were programmed to detach after completing 1 to 16-month missions recording pressure (depth) and water temperature.ResultsSix tags failed to report, and among the remaining 44 reporting tags, 34 reported on schedule, up to 487 days at sea – the longest electronic tag deployment for this species to date. Although the majority of PSATs reported within 50 km from the release sites, confirming high site fidelity, 12% of tags reported more than 200 km away, showing connectivity to Shag Rocks and South Georgia in the Southern Ocean. Toothfish moved across the Antarctic Polar Front through/to areas with no fishing activities, and hence, explained the absence of any previous conventional tag recapture. A 1-month transit to the Falkland/Malvinas Plateau Basin also revealed that toothfish can attain a surprisingly high movement rate of 33 km day-1.DiscussionFishery independent examples of toothfish presence and their movement capabilities are inviting us to broaden our examination on how toothfish move around their Scotia Arc habitats and link up different regional aggregation sites in the South Atlantic.

Simultaneous, vision-based fish instance segmentation, species classification and size regression.

Overexploitation of fisheries is a worldwide problem, which is leading to a large loss of diversity, and affects human communities indirectly through the loss of traditional jobs, cultural heritage, etc. To address this issue, governments have started accumulating data on fishing activities, to determine biomass extraction rates, and fisheries status. However, these data are often estimated from small samplings, which can lead to partially inaccurate assessments. Fishing can also benefit of the digitization process that many industries are undergoing. Wholesale fish markets, where vessels disembark, can be the point of contact to retrieve valuable information on biomass extraction rates, and can do so automatically. Fine-grained knowledge about the fish species, quantities, sizes, etc. that are caught can be therefore very valuable to all stakeholders, and particularly decision-makers regarding fisheries conservation, sustainable, and long-term exploitation. In this regard, this article presents a full workflow for fish instance segmentation, species classification, and size estimation from uncalibrated images of fish trays at the fish market, in order to automate information extraction that can be helpful in such scenarios. Our results on fish instance segmentation and species classification show an overall mean average precision (mAP) at 50% intersection-over-union (IoU) of 70.42%, while fish size estimation shows a mean average error (MAE) of only 1.27 cm.

Stock Assessment and Virtual Population Analysis of Carassius auratus (Linnaeus, 1758) in the Al-Diwaniya River, Middle of Iraq

A total of 1128 individuals of C. auratus were collected from the Diwaniyah River, Iraq. Samples were collected between November 2016 and October 2017 using different fishing gears aiming to assess the stock assessment and virtual population analysis. Fish length ranged from 8.0 to 33.0 cm, with a length-weight relationship exhibiting positive allometric growth. Asymptotic length (L∞) was estimated at 33.0 cm, the growth coefficient (K) was 0.16, and the growth performance index (Ǿ) was 2.241. The values of total (Z), natural (M) and fishing (F) mortality rates were 0.89, 0.47, and 0.42, respectively. The exploitation rate (E) was 0.48. Length with a 50% probability of capture (LC50) was estimated at 18.7 cm and was higher than the length at first maturity (Lm50). The recruitment consisted of one seasonal pulse from April to July. The exploitation rate (E) was below the biological target reference points (E0.1 and Emax), indicating the stock was under exploitation state. The result of the virtual population analysis revealed that most of the fishing mortality happened in mid-lengths (18-26 cm) with a maximum rate at a length of 25 cm. Natural losses were highest among individuals within the length range of 8.0 to 15 cm and then decreased gradually to the length group of 30. For management purposes, this study suggests that more yields can be obtained by increasing the fishing activities on this invasive species, such as increasing the number of fishing boats and decreasing the mesh size to decline its abundance in the long term.

The spatio-temporal distribution of small-scale fisheries along the northern Panay Gulf, Philippines: Implications for management

The small-scale fisheries along the northern region of the Panay Gulf face a distinctive challenge as multiple communities compete for access to the same fishing areas and resources. In response, neighboring coastal municipalities implemented conventional management measures, such as Marine Protected Areas (MPAs) and seasonal closures, aiming to enhance the abundance of fisheries resources. However, these measures only imposed economic hardships on artisanal fishermen. To address this issue, a survey involving 135 informants from coastal barangays was conducted between June to November 2021. The study used semi-structured questionnaires and GPS data loggers to collect essential information on the spatial and temporal distribution of fishing activities and specific target catches. The integration of local knowledge played a crucial role in bridging critical data gaps within the study site, facilitating the identification of more effective management reforms. The findings revealed that traditional harvest locations for various gear types exhibited zonation patterns across the gulf. Fishing activities were strategically conducted in areas with available resources, often disregarding municipal fishing boundaries. Coordinated management strategies are deemed imperative due to the varying timing of seasonal closures among municipalities. On the other hand, the temporal analysis of fishing activities revealed peak seasons of fisheries resources, providing a basis for adjusting the selection of target species and the duration of seasonal closures. Interestingly, the existing management measures failed to reduce the annual fishing activities and were ineffective, contrary to popular claims. This outcome was primarily due to constant shifts in the types of fishing gear used and target catches between seasons, highlighting the displacement of exploitation. In conclusion, this study underscores the importance of aligning fisheries policies with the dynamic nature of small-scale fisheries. Unless these policies adapt to the evolving conditions of the sector, they are likely to remain ineffective in addressing issues faced by artisanal fishermen in the region.

Fisheries observers: An overlooked vulnerability for crime and corruption within the global fishing industry

Human fishery observers play an important role in monitoring fish stocks, providing scientific data upon which management organizations set applicable fishing limits and quotas to maintain sustainable populations. At-sea observers, however, sometimes sustain harassment from crews that object to being monitored, and at least one observer has disappeared or died under suspicious circumstances while underway every year since 2009. This exploratory paper examines inherent vulnerabilities within the monitoring, control, and surveillance (MCS) framework that nations and regional fisheries management organizations (RFMO) have adopted to support sustainable fish stocks. As rational actors, perpetrators of observer harassment, assault, and murder likely do so to manipulate observers’ monitoring role in the MCS framework to conceal illegal, unreported, and unregulated (IUU) fishing and other criminal activities. Qualitative analysis of reporting on observer harassment and suspicious disappearances over the past 15 years indicates the following institutional, situational, jurisdictional, and physical conditions appear to contribute to observer safety issues—privatization of fishery observer programs, crime convergence on fishing vessels, conflicting maritime jurisdictional considerations, and harsh conditions endemic to the remote maritime environment. While recorded suspicious observer deaths are too few to draw general conclusions, most occurrences befell observers working for tuna RFMOs in the Pacific Ocean, and a disproportionate number of deaths were observers from Kiribati and Papua New Guinea. Alternative surveillance approaches such as Remote Electronic Monitoring (REM) produce limited results without human observers. Future policies that could contribute to observer safety include applying lessons learned from international efforts to address maritime transnational organized crime and providing observers personal communications and safety equipment to directly connect with search and rescue entities if under duress.

Biological-based techniques for real-time water-quality studies: Assessment of non-invasive (swimming consistency and respiration) and toxicity (antioxidants) biomarkers of zebrafish

Swimming consistency and respiration of fish are recognized as the non-invasive stress biomarkers. Their alterations could directly indicate the presence of pollutants in the water ecosystem. Since these biomarkers are a routine process for fish, it is difficult to monitor their activity manually. For this reason, experts employ engineering technologies to create sensors that can monitor the regular activities of fish. Knowing the importance of these non-invasive stress biomarkers, we developed online biological behavior monitoring system-OBBMS and online biological respiratory response monitoring system-OBRRMS to monitor real-time swimming consistency and respiratory response of fish, respectively. We continuously monitored the swimming consistency and respiration (OCR, CER and RQ) of zebrafish (control and atrazine-treatments) for 7 days using our homemade real-time biological response monitoring systems. Furthermore, we analyzed oxidative stress indicators (SOD, CAT and POD) within the vital tissues (gills, brain and muscle) of zebrafish during stipulated sampling periods. The differences in the swimming consistency and respiratory rate of zebrafish between the control and atrazine treatments could be precisely differentiated on the real-time datasets of OBBMS and OBRRMS. The zebrafish exposed to atrazine toxin showed a concentration-dependent effect (hypoactivity). The OCR and CER were increased in the atrazine treated zebrafish. Both Treatment I and II received a negative response for RQ. Atrazine toxicity let to a rise in the levels of SOD, CAT and POD in the vital tissues of zebrafish. The continuous acquisition of fish signals is achieved which is one of the main merits of our OBBMS and OBRRMS. Additionally, no special data processing was done, the real-time data sets were directly used on statistical tools and the differences between the factors (groups, photoperiods, exposure periods and their interactions) were identified precisely. Hence, our OBBMS and OBRRMS could be a promising tool for biological response-based real-time water quality monitoring studies.