Mesh Size Regulation Research Articles

Stock Assessment of <i>Oreochromis niloticus</i> and <i>Clarias gariepinus</i> from River Hadejia, Jigawa State

The study aimed at assessing the fisheries potentials of Hadejia River. Data on the captured of the fishes were collected over a period of five weeks using gill nets of various mesh sizes, with the assistance of the fishermen. A total of twenty five different fish species belonging to 14 families were identified. The family Cichlidae dominated the fish fauna with 54%. The families Claridae constituted 20%, while the others were the least with only 26%. The fish caught per day was about 1,308 from six landing sites, with 14 fishermen operating averagely from each site. The study also revealed that the river was partially over-fished. Fish samples were collected weekly for five weeks period, from the sampling station using fishing gears of various mesh sizes (3, 4, 5, 6, 7, 8 centimeters), with the assistance of the fishermen. Fish samples were identify and weighed fresh, at landing sites to the nearest gram. Standard and total lengths were taken using a measuring board and also the diversity of fish recorded in this study indicates that the River has relatively high fish diversity. The number and biomass of fish caught during the study is considered high, when compared to other Nigerian Rivers. The sizes of fish recorded also indicate that the River is been over fished. It is therefore recommended that the government and other donor agencies should provide support for research and studies to collect analyze and synthesize information and harmonize existing policies, edicts and byelaws that conform to Integrated Water Resources Management (IWRM) principles, including establishing criteria for water use. The artisanal fishermen should also be encouraged to maintain the use of mesh size regulation.

An assessment of observer deployment on industrial trawlers in Ghana

The most reliable way of monitoring fisheries performance is by a standardized reporting of relevant data by well-trained observers. The Fisheries Enforcement Unit (FEU) of Ghana has trained about 200 observers for deployment on Ghanaian flagged trawlers to curb illegalities committed during fishing expeditions and also to collect data that cannot be taken when using the Vessel Monitoring System (VMS). These observers were deployed on 831 trips of industrial trawl vessels for fishing expeditions from July 2015 to March 2019. Total (100%) on-board observer coverage, however, started from March 2018 since January and February were declared as closed season. Using the catch data from March to December 2018, a sub-sample of 162 observer trips out of the 543 observer trips in 2018 was compared to catch data declared and landed by the trawler operators. Observers declared a total of 19,771.08 tonnes of fish against total tonnage of 16,468.21 declared by trawler operators indicating a difference of 3,302.87 tonnes between them. This difference in tonnage is significant and it represents 20% increment in the data presented by the observers. There is also 75.6% correlation between the two data sources and this shows a strong linear relationship. Forty-six (46%) of the total catch recorded was by-catch and this figure is quite alarming. The trawler operators obeyed the minimum fishing gear mesh size regulation of 60 mm and fishing depth beyond 30 meters. The total observer coverage has helped to overcome observer effect and also reduced bias in data collection. Data submitted by these observers provide useful complimentary information on the state of a fish stock.

Closed season policy in Visayan Sea, Philippines: A second look

The state of marine resources is declining globally. In the Philippines, a closed season policy is one of the management strategies being implemented for the conservation and protection of marine resources. This paper presents the results of a study conducted to examine the closed season policy in the Visayan Sea and find out whether or not it has led to the attainment of the protection and conservation objectives stipulated in the policy.Stakeholders of sardine fishing through a purposive sampling technique were interviewed using a pre-tested questionnaire. Results reveal that stakeholders of the sardine industry have different perceptions on whether or not the regulation led to an increase in fish production. Catch per unit of effort (CPUE) of the fisher-respondents substantially decreased. On the other hand, processors and traders perceived that the sardine production increased. Data from the Philippine Statistics Agency show that there is no significant increase in the country's total sardine production.The closed season policy has economic implications, which led to non-compliance. Thus, there is a need to provide livelihood programs to diversify the source of income of the stakeholders who are highly dependent on sardine fisheries. For closed season to be effective it has to be applied along with other management strategies such as mesh size regulation, establishment of Marine Protected Areas, and provision of alternative sources of livelihood.

Noncompliance a Major Threat in Fisheries Management – Experience from the Artisanal Coastal Fisheries of Bangladesh

Non-compliance with regulation is a major problem that undermines the effectiveness of the coastal fisheries management in Bangladesh. The result of non-compliance with regulation is over fishing, resource depletion, habitat degradation and resource use conflicts. From a management perspective, it is important to examine the level and causes of non-compliance and explore policies for encouraging or securing compliance. An attempt has been made in this study to investigate these issues in the case of the marine fisheries of Bangladesh. The specific area of interest is the mesh size regulation. Result showed an absolute violation of the mesh size regulation. The study found that the opportunity of getting higher catches and economic returns, weak enforcement, influence of the social environment, ignorance about the law and limited livelihood opportunities are the main causes behind the noncompliance of the fishers with respect to mesh size regulation.

Sustaining Food Production: Fisheries Management Options for Lake Ardibo, Northern Ethiopia

Lake Ardibo is one of the important freshwater lakes in northern Ethiopia and today it supports many fishers and their families, who are directly depend on the lake fishery for their protein food source and income generation. The open nature of the fishery resource and high unemployed youth participation in the fishing activity is urgent call and in the long term the lake fishery may become overexploited and collapse so there is a need to introduce some management options for the lake by assessing the current condition using fishermen and key expert interviews as well other secondary data assessment and after this using simple excel sheet and expert analysis were used to compile this paper. Hence based on the analyzed data and observation the fishermen are welling to practice licensing, mesh size regulation, gear restriction and closed season in lake Ardibo fishery. Finally, the researcher recommend that the fishermen should aware about the fish stock resource condition i.e. their market size of the fish, breeding season, area and practices for the sustainable food production from the lake and lastly the regional fishery proclamation should be enforced and applied on the ground.

Assessing on coastal fishing activities and marine resources in Tuy An district, Phu Yen province

Studying on fishing activities and marine resources protection in general, fishing in coastal area in particular play an important role in order to support fisheries authorities to proposing the reasonable solutions that based on scientific results. This study have implemented the case study of fishing activities on coastal of Tuy An district, Phu Yen province. The result showed that number of fishing boat was fluctuate from 1,172 in 2014 to 1,032 in 2018, mainly boats of range of less than 20 HP that account for around 51.4%, the range of 45 – 90 HP occupies about 7.6%. The mostly fishing gear is gill-net (56.8%). The fishing boats violated minimum mesh-size regulations are very popular, for example, mesh-size of lobster seed driftnet is smallest at 2 mm. Many fishing boats were IUU fishing such as trawl, driftnet etc. Also, fishermen’s awareness are low and limited in terms of fishing activities and resource protection that is cause of crucial decrease of marine resources. The solutions should be noted that alternatives, studying the marine resources stock, enhancing the fishermen awareness to sustainable fisheries.
 Key words: fishing activities, marine resources, Tuy An district, Phu Yen province

Codend selectivity in the East China Sea of a trawl net with the legal minimum mesh size

Selectivity curves were obtained for 22 species of fish and squid from stock assessment research data for the East China Sea between 2001 and 2011, conducted using a cover net attached to the codend of a trawl net (Seikai National Fisheries Research Institute SS-RI-type trawl net). The trawl net codend was made of diamond mesh net with a legal minimum mesh opening size of 54 mm (mesh length of 66 mm). A cover net with a mesh opening of 18 mm (or 10.3 mm depending on the research year) was attached to the codend. For each of the 20 fish species and two squid species, we pooled data of hauls where body size for the whole catch was measured without subsampling to obtain the body size compositions of fish caught in both the codend and the cover net. The maximum likelihood method was performed for estimation of parameters in the logistic curve equation representing the codend selection curve. For 18 fish species (excluding Trichiurus japonicus and Muraenesox cinereus), we examined the relationship of the obtained selection parameters [length at 50% retention (l50) and selection range (SR) (= l75–l25)] to fish body shape. We demonstrated that, in fish species with a smaller ratio of body height/width to body size (i.e., more slender body type), there was a tendency for larger l50 and SR. Furthermore, by comparing the l50 of each fish species with reproductive parameters such as minimum length at maturity, we examined the sustainability of the resources based on the minimum mesh size regulation.

Quantifying the morphology of key species caught in the southern Brazilian penaeid trawl fishery as a precursor to improving selection

Penaeid trawls are poorly selective fishing gears; contributing towards approximately 27% of global marine fisheries discards. Various options are available for mitigating penaeid-trawl bycatch, including gear modifications such as ‘bycatch reduction devices’ (BRDs) or codend mesh-size regulations. A precursor to developing modifications is information about the key target and bycatch species in terms of their sizes and morphology. Here we describe the relationships between these characteristics for the southern Brazilian industrial penaeid-trawl fishery within a broader objective of proposing more selective trawl configurations. Catches were sampled during 37 tows. Fifty-two species were caught, including two loggerhead turtles, Caretta caretta , one green turtle, Chelonia mydas , as well as 61 individuals of seven ray species classified as Endangered or Critically Endangered. One penaeid ( Pleoticus muelleri ) and 11 teleosts were assessed for various morphological relationships. The data demonstrated that both the existing conventionally used 26 mm (stretched mesh opening; SMO) mesh and a legislated size of 30 mm SMO are too small. Using morphological relationships, we propose testing a minimum diamond-shaped mesh size of at least 35 mm and a square-mesh window in the top of the codend comprising at least 48 mm mesh. Such a configuration would probably retain penaeids and larger teleosts, but allow many small teleosts to escape. Anteriorly located grids are also required to reduce the bycatch of charismatic species like turtles and rays. Wide-scale use of such BRDs should considerably reduce bycatches and the ancillary impacts of regional penaeid-trawl fisheries.

Assessment of fishing gear and catch rate in Oguta Lake, south Eastern Nigeria

This study was carried out in Oguta Lake, Imo State, Nigeria, from January, 2012 to December, 2013 at five stations (Onu Utu, Okposha, Ogbe Hausa, Osemotor and Ede Ngwugwu) to ascertain the percentage abundance and catch rate of gear and craft. The average weight of fish caught per canoe per day ranged between 3.2 kg for Basket and Drum traps to 47.1 kg for boat seine net. The gill nets ranged between 6.0 to 13.0kg per canoe per day with mean weight of 8.60±2.91kg, the cast net had values ranging from 1.0 to 7.0 kg with a mean weight of 4.3±2.49 kg. Lift net yielded an average of 3.4 kg per canoe per day. Gill nets were the main gear used by fishers, followed by long lines and cast nets at the lake. It is important to locate all the fishers operating in the lake and daily record of catches be collected for a more accurate picture of the total catch and fish species. Mesh size regulation prevent over exploitation of young fish, before they attain sexual maturity. It is recommended that the cost of procuring fishing inputs such as fishing gear and crafts and safety kits should be monitored by government and be subsidized for the fishers.Key words: drum trap, crafts, catch, exploitation, Oguta, mesh size, trap

Population dynamics of Sardinella aurita (Val., 1847) within Ghana’s coastal waters

Following the declining stocks of Sardinella aurita within the coastal waters of Ghana, this study aimed at examining some population parameters of Sardinella aurita as a guide for managing this important stock sustainably. Length-frequency data of 717 samples were obtained from June, 2014 to January 2015 and measured for total length with the resultant data analyzed using FiSAT II. The asymptotic length (L∞) and growth rate (K) were 21.53 cm SL and 0.25yr-1 respectively. The theoretical age at birth (t0), longevity (tmax) and growth performance index (ϕ) were -0.74yr-1, 12 years and 1.849 respectively. Total mortality rate (Z), natural mortality rate (M) and fishing mortality rate (F) were 3.17, 0.76 and 2.41yr-1 respectively. The ages at first recruitment and first capture signaled future collapse of the stock, in the absence of proper management interventions. VPA outcome showed that mid- lengths of 11 cm and 12 cm SL experienced the highest harvesting rate with MSY estimated at 7733 tons. The recruitment pattern was continuous with two major recruitment pulses. Exploitation rate (Ecurr=0.76) was higher than the maximum exploitation rate (Emax=0.56), indicating unsustainable exploitation. Further, the fishing regime fell within the overfished stage based on the Quadrant Rule. For sustainable exploitation of this commercial fish species, implementation of relevant biological reference points through reduction in fishing efforts, creation of marine protected areas and mesh size regulation are urgently advocated.Res. Agric. Livest. Fish.4(3): 237-248, December 2017

Güllük Körfezi’nde kullanılan fanyalı uzatma ağlarında (80 ve 90 mm ağ göz boyu) dil balığı (Solea solea linnaeus, 1758) seçiciliği

This study was aimed to determine that the selectivity parameters of sole trammel nets which are used in Güllük Bay where is one of the important fishing grounds in Turkey. Samplings were realized between November 2013 – December 2015 with trammel nets stretched mesh size with 80 and 90 mm. Totally 1209 samples were caught. SELECT method was used to determine the selectivity parameters. Bi-modal was the best fitted our data. Optimum lengths for 80 and 90 mm trammel nets were found as 23 and 27,02 cm, respectively. Also, for 80 and 90 mm trammel nets, length at first capture values (Lc) were estimated as 20,37 and 21,11 cm and CPUE values were calculated as 2,94 and 1,43 kg/1000m, respectively. As it seen from CPUE values, fishing pressure effects large-sized individuals. This situation means decreasing in spawning stock biomass and number of small-sized individuals that provide continuance of generations, will be less than now when considered natural and fishery mortalities. In commercial fishery laws, size limitation for common sole is 20 cm. Length at first capture values are too close to limitation. So, there is no need for any application toward mesh size regulation but on number of trammel net panels, a serious regulation is needed.

An Assessment on Economic Impact of Growth Over Fishing of Commercially Important Marine Ariids Along Mumbai, Northwest Coast of India.

The economic assessment on juvenile landings of four dominant marine catfishes at New Ferry Wharf (NFW) landing centre, Mumbai, Northwest coast of India was carried out during January to December, 2013. The dominant catfishes viz. Nemapteryx caelata (19.7 %), Plicofollis dussumieri (21.5 %), P. tenuispinis (24.8 %) and Osteogeneiosus militaris (27.5 %) together contributing 93% of total marine catfish landings of the state. Among four species, the juvenile landings of N. caelata contribute maximum(93.17 %) followed by P. dussumieri (57.14 %), O. militaris (36.11 %) and P. tenuispinis (21.43 %) with the maximum landing during November to March . The bioeconomic model reveals that if juveniles are allowed to grow up to length at first maturity (Lm); an estimated total annual economic gain will be Rs. 13.15 crores with an estimated biomass gain of 1222 t per annum. The estimated total annual biomass is increased by 2.07 times with an increase in additional revenue by 3.7 times would have been realised. The results of present study suggest that sustainable harvest of these resources would have been yielded maximum economic return to the fishers. With the help of stakeholders participatory approach, management measures such as strict mesh size regulation, effort restriction on bottom trawl up to 50 m depth and awareness campign on catching juveniles and adult in particulat to the oral incubated male ariids, would have been implemented during November to March to avoid growth over fishing.

Biologi Reproduksi Ikan Belida (Notopterus notopterus Pallas, 1769) di Kolong-Bendungan Simpur, Pulau Bangka

The knowledge of fish reproduction is the most important in freshwater management continously. The research was done from February-July 2013, was aiming to describe information on reproductive aspects of belida fishes (Notopterus notopterus),i.e. sex ratio, gonado somatic stages, gonado somatic index, first size of maturity, fecundity, and spawning type. The fish Samples was taken by gill net which had many sizes such as 2, 2.5, 3, and 4 cm. Each gill net has length 30 m and width 2 m. Belida fishes have caught during research amounted 497 ind, which consisted of: 237 male and 260 female. Sex ratio male and female fish were relatively balance. The maturity gonad of male fish is faster than female fish. Featherback do spawn every month for each observation during the research. The spawning type of Featherback is partial pattern (step by step). The first size of maturity gonad from male fish was in length 135 mm and female fish was in length 162 mm. Fecundity of Featherback was in range 1.051-6.057 eggs. Fecundity is not influenced by length or weight body. For the sake to keep Featherback population needed a regulation, such as: the mesh size regulation of gillnet have to 30 mm or equal with 1.5 inci.

SOCIOECONOMIC AND LIVELIHOOD ANALYSIS OF HILSA FISHERS OF LOWER STRETCH OF GANGA

The present study was conducted to understand the socio-economic and livelihood features of the hilsa fishers in Hooghly-Bhagirathi river system and also to find out the reasons of decline in hilsa fishery as perceived by the fishers. Results of the analysis revealed that 60% of the hilsa fishers belonged to jele/malo community and the average experience in hilsa fishing was for about 20 years. Hilsa fishery contributed 38.84% in annual family income of fishers’ households. Lower hilsa catch in Hooghly-Bhagirathi river system during the past ten years led to large scale forced migration among the fishers’ community. The younger generation of fisherfolk had lost their interest from fishery particularly of hilsa fishery due to uncertain income. Six reasons behind decline of hilsa fishery as perceived by the fishers were documented and ranked. According to the fishers, ‘use of destructive fishing gears’ (mean score 66.06) was ranked as first among the reasons behind decline in hilsa fishery followed by ‘erratic rainfall’ (64.54); ‘huge catch of hilsa fish in lower part of Hooghly/sea mouth’ (60.3); ‘industrial pollution in Hooghly River’ (52.3) and ‘freshwater discharge/influx’ (35.07). Poor implementation of mesh size regulation, poor enforcement of closed season in rivers, ineffective extension services, and recurring climatic hazards made the hilsa fishery more vulnerable. The government, fishery cooperatives, NGOs and other related organisations need to join hands to support the hilsa fishers for sustainable hilsa fishery management.

English

Beach seine is known to be biologically and ecologically destructive. Over the years there have been increased concerns from fishery managers and stakeholders in West Africa and beyond to reduce this destruction of fish resources by the gear. Total bans for periods in the year or the use of a bigger mesh size (25 mm) at the cod end have been investigated. A covered cod end experiment was conducted in the nearshore waters at Tsokome near Accra (Ghana) during June and September 2012 to contribute to find a solution to the management problem posed by the gear. The temporal variability of effort, catch, species composition of the 10 mm and 25 mm cod ends; the gear selectivity; and the revenue of each bag were studied and compared. A total of 60 species belonging to 35 families was recorded. The four dominant taxonomic families were: Penaeidae, Carangidae, Haemulidae and Trichiuridae in order of importance. The selection factors were high and almost the same for the dominant species Brachydeuterus auritus, Chloroscombrus chrysurus and Peneaus notialis. This suggests the need to raise the Lc through adoption of increased mesh size regulation. The use of the 25 mm bag was 25% more financially rewarding than that of 10 mm bag. The 10 mm bag was found to catch species of smaller size. Educational programmes for all relevant stakeholders about the gains of using a bigger mesh size at the cod end and immediate strict enforcement of the relevant provisions of the Fisheries Law 2002, Act 625 of Ghana are among the recommendations to help save fish resources from further degradation. Key words: Beach seine gear, cod end, fish resource, fisheries management, gear selectivity, Ghana.

Productivity change under the vessel buyback program in Korean fisheries

Korean fisheries are managed mainly by input controls, such as limited licenses, and technical measures such as gear restriction, closed areas, and mesh size regulation. Despite these efforts, stock biomass has declined in the waters of South Korea leading the government to implement a fish restocking plan as well as a vessel buyback program. There has been a debate over the buyback program, its effectiveness and whether it should be for offshore vessels or coastal vessels. To address these concerns, we used a Data Envelopment Analysis method and showed which fisheries are over- or underproductive. To investigate the effectiveness of the buyback program, data were collected for 18 fisheries (nine each of coastal and offshore fisheries) from 1992 to 2012. A distance function approach was used, because the data for this time period consisted of input (number of vessels and tonnage) and output (fish harvest) values, with no corresponding input prices. Since there is a dearth of cost data and questionable market price data in fisheries, the Malmquist index (MI) was calculated to study productivity of the fisheries. Results showed two coastal fishery sectors and one offshore fishery need more intensive management. The Korean government has introduced a fish stock rebuilding plan in parallel with the vessel buyback program. The MI is a useful tool to show how productivity has improved with the two management tools working together.

Effect of mesh size on baited trap catch composition for noble crayfish (Astacus Astacus)

Minimum size is a common management regulation in noble crayfish (Astacus astacus ) fisheries. The most used catching method baited traps, catch crayfish down to 50 mm total length (TL). In Norway the minimum size is 95 mm TL and this regulation allow female crayfish to spawn a least once before being harvested. To reduce the fraction of non-legal sized crayfish in trap catches, mesh-size were increased from 17.5 to 21 mm (knot to knot) in Lake Steinsfjorden (1983) and nationwide (2001). We compared catch per unit effort data in traps with different mesh sizes from the two most important noble crayfish fisheries in Norway to evaluate the effects of the regulation. Traps with mesh size 21 mm catch significantly fewer crayfish compared to traps with 17.5 mm and 12 mm. As intended, traps with 21 mm caught significantly less non-legal sized crayfish compared to 17.5 mm. Increased mesh size thus reduce the catch-induced mortality of non-legal sized crayfish, resulting in a larger spawning population. Mesh size regulations is an important management tool, especially for recruitment limited crayfish population, and is rather easy to enforce compared to minimum size.

Survey on Penaeidae Shrimp Diversity and Exploitation in South East Coast of India

The assessment of Penaeidae species diversity in a particular region is very important in formulating conservation strategies. In the present study, the survey on diversity of Penaeidae species in south east coast of India has been assessed on the basis of landing of variety of species in this group. Penaeidae species were collected from various main landing centers of south east coast of India for three years. Identification and nomenclature was done based on previously published literature. Among the 59 species observed, the Penaeus semisulcatus, Penaeus monodon and Fenneropenaeus indicus were found mostly in all landing centers. As first and foremost, the Metapenaeus papuensis, Metapenaeus anchistus, Metapenaeopsis wellsi, Parapenaeopsis sinica (Kishinouyepenaeopsis amicus), Parapenaeopsis hungerfordi, Parapenaeopsis venusta, Parapenaeopsis coromandelica, Parapenaeopsis gracillima, Trachysalambria longipes and Parapenaeus lanceolatus landed in south east coast of India. As far as Penaeidae shrimp diversity is good in south east coast region of India, and needed the fishing site and mesh size regulation to protect the juvenile and adult of Penaeidae from inshore and offshore catching.

An overview of marine fisheries management in China

China is the world's largest country in terms of fish production, yet its fisheries management is comparatively unknown outside the country. This article gives an overview of the current management system and highlights some of its challenges. In the past 30 years, the Department of Fishery Administration has formulated and organized a series of conservation and management regimes and measures. The most important tools are minimum mesh size regulation and a range of input control measures, including seasonal closures and attempts to control fishing capacity through licensing and limiting total engine power. However, fisheries output is only controlled through a nation-wide total catch limit. Certain progress has been achieved, but there are still problems as the resource situation is poor. While the existing measures could, in principle, improve sustainability, their enforcement is insufficient, and they do not limit fishing effort in a way that would allow recovery.

Growth and mortality parameters of P. senegalensis and P. typus (Sciaenidae) in nearshore waters of Benin (West Africa) and their implications for management and conservation

Most fisheries in Africa are overexploited or are at the peak of exploitation. A key contributor to this overfishing is poor data on fisheries, inefficient management strategies and unenforced policies. Pseudotolithus species off Benin nearshore waters are mainly fished by beach seining. Unfortunately, since 1994, the production of these species has been decreasing, with more small-sized fishes appearing in catches, and little is known about the species’ population dynamics. Therefore, the growth and mortality parameters of two commercially important Sciaenids (Pseudotolithus senegalensis and Pseudotolithus typus) off Benin's nearshore waters were investigated using length–frequency data of 2019 specimens sampled from beach seine hauls over a period of 18 months. The length–weight relationship was computed from linear regression analysis. P. senegalensis exhibited isometric growth while P. typus exhibited negative allometric growth. The von Bertalanffy growth constants for P. senegalensis were TL∞=51.4cm, K=0.24yr−1, and t0=−0.60yr with a derived growth performance index of φ′=2.753. The corresponding estimates for P. typus were TL∞=56.2cm, K=0.19yr−1, t0=−0.73yr and φ′=2.652. The growth patterns determined by the growth performance index (φ′) were higher for P. senegalensis than for P. typus of similar sizes. The total mortality rate, Z, for P. senegalensis was estimated as 4.39yr−1, with the fishing mortality, F, being calculated as 3.70yr−1. The mortality estimates for P. typus were Z=4.12yr−1 and F=3.70yr−1. The exploitation rate of the two fish species was higher than the optimum exploitation criterion, which is indicative of over-fishing. Several immediate management actions, such as size-limit regulation by gradually increasing beach seine mesh size and time-limit regulation by restricting fishing outside the spawning season, are considered necessary for sustainable exploitation of these stocks.