Over the past few decades, extreme changes have occurred in the characters of exploited fish populations. The majority of these changes have affected the growth traits of fish life history, which include a smaller siz...Over the past few decades, extreme changes have occurred in the characters of exploited fish populations. The majority of these changes have affected the growth traits of fish life history, which include a smaller size-at-age, an earlier age-at-maturation and among others. Currently, the causes of these life history traits changes still require systematic analyses and empirical studies. The explanations that have been cited are merely expressed in terms of fish phenotypic adaptation. It has been claimed that the original traits of fish can be recovered once the intensity of exploitation of the fish is controlled. Sustained environmental and fishing pressure will change the life history traits of most fish species, so the fish individual's traits are still in small size-at-age and at earlier age-at-maturation in exploited fish populations. In this paper, we expressed our view of points that fishing gear has imposed selectivity on fish populations and individuals as various other environmental factors have done and such changes are unrecoverable. According to the existing tend of exploited fish individual's life history traits, we suggested further researches in this field and provided better methods of fishery management and thereby fishery resources protection than those available early.展开更多
The objective of this work is to show the benefits of a new eco-systemic fishing gear installed in three bottom trawlers after one year using it. The study has been based on fuel consumption reduction for the three ve...The objective of this work is to show the benefits of a new eco-systemic fishing gear installed in three bottom trawlers after one year using it. The study has been based on fuel consumption reduction for the three vessels and the catch in two of them. The new system minimizes the impact of the fishing gear on the seabed, with a reduction on the tow resistance. This generates significant fuel savings that improves the economical result of the fishery, helping the ship owners in the return of investment first, then in the future viability of the operation. Apart of the evident savings due to the fuel consumption reduction, in the long term, the ship owner will notice also savings on maintenance, both because the winches are towing with less tension （longer life for warps, brakes and hydraulic system） and the engine is running at low rpm＇s （longer life of the engine and between breakdowns）. The new fishing gear does not require any modification on the way that the fisherman is working, only replacing and/or modifying some parts or components of the fishing gear. The implementation is easy and the adjustments required could be done in a couple of days.展开更多
Anchored fish aggregating devices(AFADs)have been widely used for fishing in Thai waters.However,abandoned,lost,and discarded fishing gears(ALDFGs),including lost AFADs,may cause environmental impacts.Fishing gear mar...Anchored fish aggregating devices(AFADs)have been widely used for fishing in Thai waters.However,abandoned,lost,and discarded fishing gears(ALDFGs),including lost AFADs,may cause environmental impacts.Fishing gear marking(FGM)is considered as a tool to help identification of ALDFGs.The main objective of this study is to compare the durability represented by the percentage of remaining condition(R-value)of three material types of FGM applied for AFADs,i.e.,stainless steel(SS),colored acrylic(CA),and polypropylene(PP).This study was carried out using 50 AFADs deployed in the Gulf of Thailand(GOT)and the Andaman Sea(ANS)between July and October 2020 in cooperation with 10 fishers.The AFADs were deployed in similar habitat(bottom depth and type)between the GOT and the ANS.The three material types of FGM were assumed to be sufficiently durable to last for the lifespan of the AFADs in both the GOT and the ANS(within 2 months and 3.5 months,respectively)though some FGMs in the ANS were detached from cable ties or broken before AFADs were lost.The loss of AFADs and FGMs was mainly caused by adverse weather condition(rough sea).Only data from the ANS was included in comparative analysis due to the insufficient variance data obtained from the GOT.The analysis revealed that SS had the higher durability than CA and PP when the AFADs lasted for less than 3.5 months.As a result of our study,some recommendations were made.For example,the cable ties can be replaced by ropes or threads to improve the installation method.This study serves as a basis to develop FGM and to support responsible fisheries.Beneficiaries of the study include fisheries policy makers,managers,and fishers.展开更多
The high market demand for endeavour shrimp(Metapenaeus ensis de Haan)has caused intensive fishing for this resource and tends to threaten their sustainability.Assessment of fishing dynamic and stock status of fisheri...The high market demand for endeavour shrimp(Metapenaeus ensis de Haan)has caused intensive fishing for this resource and tends to threaten their sustainability.Assessment of fishing dynamic and stock status of fisheries resource is the main point to formulate its proper sustainable management in the future.The purpose of this study was to determine the stock status of endeavour shrimp in the Bombana and its surrounding waters.The study was conducted from April to November 2021 using a survey method to analyze the length at first capture(L_(c)),length at first maturity(L_(m)),growth rate(K),maximum theoretical carapace length(Loo),and mortality rate such as total mortality rate(Z),fishing mortality rate(F)and natural mortality rate(M).The study results revealed that the endeavour shrimp growth pattern in Bombana was negative allometric and that the ratio of males and females was not balanced.The length at first capture(L_(c))was 29.83 mm(carapace length)and the length at first maturity(L_(m))was at a total carapace length of 31.67 mm.The growth rate(K)was 1.0 per year and maximum theoretical length(L_(∞))was 46.2 mm.The estimate total mortality rate(Z)was 2.52 per year,the fishing mortality rate(F)and natural mortality rate(M)were 0.91 per year and 1.61 per year respectively.The exploitation rate(E)was 0.36 per year,therefore the stock status is not categorized overfishing.In order to ensure the sustainability of the endeavour shrimp,then the effort must be increased by about 28%of the current effort.展开更多
Two fishing methods including gillnetting and trawling to estimate attributes of fish assemblage were compared in Dianshan Lake from August 2009 to July 2010. Species composition dif fered significantly between the ge...Two fishing methods including gillnetting and trawling to estimate attributes of fish assemblage were compared in Dianshan Lake from August 2009 to July 2010. Species composition dif fered significantly between the gears, with four significant contributors in gillnet catches and one in trawl catches. Trawling collected more proportions of benthic species by number and biomass than gillnetting. Size distribution was significantly influenced by fishing technique; gillnetting captured relatively less small-sized fishes and trawling captured less large-sized individuals. Trawling produced species richness closer to the one expected than gillnetting. On the whole, trawl catch was a quadratic polynomial function of gillnet catch and a significantly negative correlation was found between them, both of which varied as dif ferent polynomial functions of temperature. However, trawl and gillnet catches were significantly correlated only in one of five month groups. It is concluded that single-gear-based surveys can be misleading in assessments of attributes of fish assemblages, bottom trawling is a more ef fective gear for assessing fish diversity than benthic gillnetting, and using gillnet catches as an indicator of fish density depends on fishing season in the lake.展开更多
Species richness and human activities in natural environments are among the most important recreational needs. Monthly studies of aquatic fauna, artisanal fisheries and tourism characteristics was conducted during wet...Species richness and human activities in natural environments are among the most important recreational needs. Monthly studies of aquatic fauna, artisanal fisheries and tourism characteristics was conducted during wet and dry seasons, over a two year period in the three landscapes along the 6817.7 m length of Agbokum waterfalls by using a close-ended pre-coded survey instrument. Through MANOVA analysis of the 1780 respondents we found strong positive association between peoples visits to the recreational areas and the type of landscape in which the respondents felt happy. People who felt happier in landscape dominated by waterfalls, visit the middle reaches of the river for outdoor recreation more often while people who feel happy in landscapes dominated by slow water current with an extensive wide area and floodplains, visit downstream reaches of the waterfalls more often. Activities performed more often along downstream reaches include fishing, bathing/swimming, boating and hunting while more frequent activities in the middle reaches (waterfalls) include taking photographs, picnics, enjoying nature, outing with family and friends, looking at view, resting and relaxing. A total of 5484 fish representing 22 species belonging to 16 genera from 9 families were sampled with 10 species being restricted to wet season and only 1 in the dry. The number of taxa and individuals present at upstream, midstream and downstream reaches were 16 (2003), 13 (1034), 17 (2447), respectively. Tilapia zillii, Clarias gariepinus and Labeo coubie dominated overall catch constituting 35.5%. Twenty five operational boats counted during the period of study, were only used downstream by 25 full-time fishermen, 87 part-time, 44 shoreline fishermen and 36 assistant fishermen. Common gears were the hook and line constituting 45.8%, cast and dip net (10.1%) bailing (8.7%), gill nets (7.3%), seine net (6.4%) Traps (5.5%), lift net (4.7%) Dip nets (0.9%), poisoning (2.8%), cutlass (3.3%) and spear (1%). Seasonally occurring aquatic fauna include crustaceans (Atya gaboneensis and Palaemon paucidens) (23.5%) oysters (Etheria elliptica) (15.4%), clams (Galacea paradoxa) (20.8%), Manatee (Trichechus senegalensis) (2.5), Hippopotamus amphibious (1.8%), Otter (Lutra macullicolis) (0.5%), Crocodyles (Crocodylus niloticus, Crocodylus cataphractus (Aligata) and Osteolaemus tetraspsis) (18.8%). The nile monitor (Varanus nilaticus), aquatic snake (Anoscopus sp), and three species of water turtle (Kimxys erosa, Pelumedusa sp and Peliosus sp) (21.6%). Relatively higher faunal densities and species richness in the upstream and downstream reaches coupled with waterfalls in middle reaches can makes Agbokum waterfalls a tourism destination if only management strategies include Legislation to conserve these natural resources.展开更多
The Lom Pangar hydroelectric dam project located in the eastern region of Cameroon was implemented by Electricity Development Corporation (EDC). The impoundment of the Lom Pangar dam created a large reservoir with an ...The Lom Pangar hydroelectric dam project located in the eastern region of Cameroon was implemented by Electricity Development Corporation (EDC). The impoundment of the Lom Pangar dam created a large reservoir with an area ~590 km2 and a useful storage capacity ~6 billion m3. Thereby, this impoundment has created favourable conditions for the proliferation of fishery resources. However, a fisheries assessment study based on fishing activities is essential to attain reliable information for implementing a management plan to achieve rational and sustainable exploitation. This study was carried out on the ichtyofaunic inventory and the assessment of fish landings in Lom Pangar hydroelectric dam reservoir from April 2016 to September 30, 2016. Three main groups of fishing gear have been identified, among which gillnets, traps and longlines occupy major fishing activities. Indeed, the spatial and landing sites surveies were conducted on species composition, size composition, and quantities of fish landed during the study period. Moreover, 37 species of fish divided into 16 families were found in seven different selected fish landing sites. Carp (Cyprinus carpio) was the major fish species abundantly caught by these fishing gears which accounted for 81.60% of the total catch, and the least species was sardine (Sardinella aurita). A total of 623,229 Kg of fish were landed which were dominated by those of the Wami landing site with 480,773 Kg representing 76.96% of the total landed catches. The smallest species caught was the white carp (7 cm) while the longest one was the catfish (71 cm). In addition, the species of fish in the breeding season are carp, catfish, viper fish and red tail.展开更多
基金the financial support from Special Fund for Agro-scientific Research in the Public Interest (No. 201203018)
文摘Over the past few decades, extreme changes have occurred in the characters of exploited fish populations. The majority of these changes have affected the growth traits of fish life history, which include a smaller size-at-age, an earlier age-at-maturation and among others. Currently, the causes of these life history traits changes still require systematic analyses and empirical studies. The explanations that have been cited are merely expressed in terms of fish phenotypic adaptation. It has been claimed that the original traits of fish can be recovered once the intensity of exploitation of the fish is controlled. Sustained environmental and fishing pressure will change the life history traits of most fish species, so the fish individual's traits are still in small size-at-age and at earlier age-at-maturation in exploited fish populations. In this paper, we expressed our view of points that fishing gear has imposed selectivity on fish populations and individuals as various other environmental factors have done and such changes are unrecoverable. According to the existing tend of exploited fish individual's life history traits, we suggested further researches in this field and provided better methods of fishery management and thereby fishery resources protection than those available early.
文摘The objective of this work is to show the benefits of a new eco-systemic fishing gear installed in three bottom trawlers after one year using it. The study has been based on fuel consumption reduction for the three vessels and the catch in two of them. The new system minimizes the impact of the fishing gear on the seabed, with a reduction on the tow resistance. This generates significant fuel savings that improves the economical result of the fishery, helping the ship owners in the return of investment first, then in the future viability of the operation. Apart of the evident savings due to the fuel consumption reduction, in the long term, the ship owner will notice also savings on maintenance, both because the winches are towing with less tension （longer life for warps, brakes and hydraulic system） and the engine is running at low rpm＇s （longer life of the engine and between breakdowns）. The new fishing gear does not require any modification on the way that the fisherman is working, only replacing and/or modifying some parts or components of the fishing gear. The implementation is easy and the adjustments required could be done in a couple of days.
文摘Anchored fish aggregating devices(AFADs)have been widely used for fishing in Thai waters.However,abandoned,lost,and discarded fishing gears(ALDFGs),including lost AFADs,may cause environmental impacts.Fishing gear marking(FGM)is considered as a tool to help identification of ALDFGs.The main objective of this study is to compare the durability represented by the percentage of remaining condition(R-value)of three material types of FGM applied for AFADs,i.e.,stainless steel(SS),colored acrylic(CA),and polypropylene(PP).This study was carried out using 50 AFADs deployed in the Gulf of Thailand(GOT)and the Andaman Sea(ANS)between July and October 2020 in cooperation with 10 fishers.The AFADs were deployed in similar habitat(bottom depth and type)between the GOT and the ANS.The three material types of FGM were assumed to be sufficiently durable to last for the lifespan of the AFADs in both the GOT and the ANS(within 2 months and 3.5 months,respectively)though some FGMs in the ANS were detached from cable ties or broken before AFADs were lost.The loss of AFADs and FGMs was mainly caused by adverse weather condition(rough sea).Only data from the ANS was included in comparative analysis due to the insufficient variance data obtained from the GOT.The analysis revealed that SS had the higher durability than CA and PP when the AFADs lasted for less than 3.5 months.As a result of our study,some recommendations were made.For example,the cable ties can be replaced by ropes or threads to improve the installation method.This study serves as a basis to develop FGM and to support responsible fisheries.Beneficiaries of the study include fisheries policy makers,managers,and fishers.
文摘The high market demand for endeavour shrimp(Metapenaeus ensis de Haan)has caused intensive fishing for this resource and tends to threaten their sustainability.Assessment of fishing dynamic and stock status of fisheries resource is the main point to formulate its proper sustainable management in the future.The purpose of this study was to determine the stock status of endeavour shrimp in the Bombana and its surrounding waters.The study was conducted from April to November 2021 using a survey method to analyze the length at first capture(L_(c)),length at first maturity(L_(m)),growth rate(K),maximum theoretical carapace length(Loo),and mortality rate such as total mortality rate(Z),fishing mortality rate(F)and natural mortality rate(M).The study results revealed that the endeavour shrimp growth pattern in Bombana was negative allometric and that the ratio of males and females was not balanced.The length at first capture(L_(c))was 29.83 mm(carapace length)and the length at first maturity(L_(m))was at a total carapace length of 31.67 mm.The growth rate(K)was 1.0 per year and maximum theoretical length(L_(∞))was 46.2 mm.The estimate total mortality rate(Z)was 2.52 per year,the fishing mortality rate(F)and natural mortality rate(M)were 0.91 per year and 1.61 per year respectively.The exploitation rate(E)was 0.36 per year,therefore the stock status is not categorized overfishing.In order to ensure the sustainability of the endeavour shrimp,then the effort must be increased by about 28%of the current effort.
基金Supported by the Science and Technology Commission of Shanghai Municipality(Nos.08DZ1203101,08DZ1203102)the Shanghai University Knowledge Service Platform,Shanghai Ocean University Aquatic Animal Breeding Center(No.ZF1206)
文摘Two fishing methods including gillnetting and trawling to estimate attributes of fish assemblage were compared in Dianshan Lake from August 2009 to July 2010. Species composition dif fered significantly between the gears, with four significant contributors in gillnet catches and one in trawl catches. Trawling collected more proportions of benthic species by number and biomass than gillnetting. Size distribution was significantly influenced by fishing technique; gillnetting captured relatively less small-sized fishes and trawling captured less large-sized individuals. Trawling produced species richness closer to the one expected than gillnetting. On the whole, trawl catch was a quadratic polynomial function of gillnet catch and a significantly negative correlation was found between them, both of which varied as dif ferent polynomial functions of temperature. However, trawl and gillnet catches were significantly correlated only in one of five month groups. It is concluded that single-gear-based surveys can be misleading in assessments of attributes of fish assemblages, bottom trawling is a more ef fective gear for assessing fish diversity than benthic gillnetting, and using gillnet catches as an indicator of fish density depends on fishing season in the lake.
文摘Species richness and human activities in natural environments are among the most important recreational needs. Monthly studies of aquatic fauna, artisanal fisheries and tourism characteristics was conducted during wet and dry seasons, over a two year period in the three landscapes along the 6817.7 m length of Agbokum waterfalls by using a close-ended pre-coded survey instrument. Through MANOVA analysis of the 1780 respondents we found strong positive association between peoples visits to the recreational areas and the type of landscape in which the respondents felt happy. People who felt happier in landscape dominated by waterfalls, visit the middle reaches of the river for outdoor recreation more often while people who feel happy in landscapes dominated by slow water current with an extensive wide area and floodplains, visit downstream reaches of the waterfalls more often. Activities performed more often along downstream reaches include fishing, bathing/swimming, boating and hunting while more frequent activities in the middle reaches (waterfalls) include taking photographs, picnics, enjoying nature, outing with family and friends, looking at view, resting and relaxing. A total of 5484 fish representing 22 species belonging to 16 genera from 9 families were sampled with 10 species being restricted to wet season and only 1 in the dry. The number of taxa and individuals present at upstream, midstream and downstream reaches were 16 (2003), 13 (1034), 17 (2447), respectively. Tilapia zillii, Clarias gariepinus and Labeo coubie dominated overall catch constituting 35.5%. Twenty five operational boats counted during the period of study, were only used downstream by 25 full-time fishermen, 87 part-time, 44 shoreline fishermen and 36 assistant fishermen. Common gears were the hook and line constituting 45.8%, cast and dip net (10.1%) bailing (8.7%), gill nets (7.3%), seine net (6.4%) Traps (5.5%), lift net (4.7%) Dip nets (0.9%), poisoning (2.8%), cutlass (3.3%) and spear (1%). Seasonally occurring aquatic fauna include crustaceans (Atya gaboneensis and Palaemon paucidens) (23.5%) oysters (Etheria elliptica) (15.4%), clams (Galacea paradoxa) (20.8%), Manatee (Trichechus senegalensis) (2.5), Hippopotamus amphibious (1.8%), Otter (Lutra macullicolis) (0.5%), Crocodyles (Crocodylus niloticus, Crocodylus cataphractus (Aligata) and Osteolaemus tetraspsis) (18.8%). The nile monitor (Varanus nilaticus), aquatic snake (Anoscopus sp), and three species of water turtle (Kimxys erosa, Pelumedusa sp and Peliosus sp) (21.6%). Relatively higher faunal densities and species richness in the upstream and downstream reaches coupled with waterfalls in middle reaches can makes Agbokum waterfalls a tourism destination if only management strategies include Legislation to conserve these natural resources.
文摘The Lom Pangar hydroelectric dam project located in the eastern region of Cameroon was implemented by Electricity Development Corporation (EDC). The impoundment of the Lom Pangar dam created a large reservoir with an area ~590 km2 and a useful storage capacity ~6 billion m3. Thereby, this impoundment has created favourable conditions for the proliferation of fishery resources. However, a fisheries assessment study based on fishing activities is essential to attain reliable information for implementing a management plan to achieve rational and sustainable exploitation. This study was carried out on the ichtyofaunic inventory and the assessment of fish landings in Lom Pangar hydroelectric dam reservoir from April 2016 to September 30, 2016. Three main groups of fishing gear have been identified, among which gillnets, traps and longlines occupy major fishing activities. Indeed, the spatial and landing sites surveies were conducted on species composition, size composition, and quantities of fish landed during the study period. Moreover, 37 species of fish divided into 16 families were found in seven different selected fish landing sites. Carp (Cyprinus carpio) was the major fish species abundantly caught by these fishing gears which accounted for 81.60% of the total catch, and the least species was sardine (Sardinella aurita). A total of 623,229 Kg of fish were landed which were dominated by those of the Wami landing site with 480,773 Kg representing 76.96% of the total landed catches. The smallest species caught was the white carp (7 cm) while the longest one was the catfish (71 cm). In addition, the species of fish in the breeding season are carp, catfish, viper fish and red tail.
