963 resultados para STOCK ASSESSMENT


Relevância:

70.00% 70.00%

Publicador:

Resumo:

This report presents findings of the CAS conducted in the Ugandan waters of Lake Victoria in May 2011. The results of the previous eleven CASs conducted under the IFMP of the LVFO programme in July, August, September and November 2005; in March, August and December 2006; in March and August 2007; in February and December 2008; and March 2010 are included to show the emerging trends. The report also presents annual catch estimates for the Ugandan part of the lake from 2005 to 2011. Through these CASs, information is building up to show the emerging picture of fish production in the Ugandan waters of the lake. Similar surveys are conducted in the Kenyan and Tanzanian parts of the lake, which provide the lake wide perspective of fisheries production but this time not simultaneously as under the LVFO effort due to different sources and timing of funding. These data can now be utilised together with other Resource and Socio-economic Monitoring survey data for a stock assessment of the lake to provide a firm basis for planning and management of the fisheries resources.

Relevância:

70.00% 70.00%

Publicador:

Resumo:

The items discussed at the meeting included; capacity development assessment techniques, development of a hilsa fishery management plan; development of a standardised model framework for stock assessment; development of a Strategic Action Plan (SAP) for ecosystem health and resource evaluation; priority fishery management recommendations; and stock status advice for hilsa in BOBLME region .

Relevância:

70.00% 70.00%

Publicador:

Resumo:

Gill-netting and rotenoning have been used for assessing and monitoring fish stock abundance in Volta Lake. The lake and the main gear types used on it have been described. Before a gill-net sampling plan was set up, a preliminary survey was undertaken which largely determined the final form of the plan. An investigation as to whether or not the lake was being overfished concluded that it was being underfished. Commercial and experimental catch data analyses disclosed that the adults of the small species were being little utilized. Commercial sized species were also not being harvested according to their apparent proportion in the population. Production is presently fluctuating between approximately 37,000 and 40,000 tonnes. A high correlation between commercial and experimental catch was realized. Developments which have followed in the wake of stock assessment and monitoring studies include: introduction of monofilament nylon net, development of a special scoop net to permit mass harvest of clupeids after they have been attracted to light, and the design of a larger canoe which would help to extend the fishery into open water. New regulation and management policies will have to be formulated in the light of new findings before a rational exploitation of all the species can be achieved.

Relevância:

70.00% 70.00%

Publicador:

Resumo:

Tese de doutoramento, Ciências do Mar, da Terra e do Ambiente (Biologia Pesqueira), Faculdade de Ciências e Tecnologia, Universidade do Algarve, 2015

Relevância:

70.00% 70.00%

Publicador:

Resumo:

Se presenta una revisión de los sucesos de las pesquerías en el lapso desde la anterior reunión del Panel en Julio, 1972 y de lo que se piensa ha tenido lugar en el recurso y en su medio ambiente; se indican diversas líneas de investigación del stock. Se resume la evidencia colateral acerca de los stocks y de su medio ambiente; ésta se relaciona con el fenómeno de El Niño, con las aves guaneras, el aumento de las capturas de sardinas, el contenido graso de la anchoveta y los estadios de maduración de la misma. Cada una de estas entidades indican que recientemente han prevalecido condiciones especiales en el ambiente de la anchoveta, en la biota asociada y en ciertos aspectos de su fisiología. Se ha hecho una detallada revisión de varios tipos de investigación de las poblaciones de anchoveta y de las evidencias que, acerca del estado del recurso, pueden derivarse de tales investigaciones. Se examinó la evidencia obtenida del uso de equipo acústico en el estudio de la distribución de stocks y en la estimación de su abundancia; el trabajo se realizó mediante exploraciones de varias embarcaciones (exploraciones Eureka) y de exploraciones especiales con el barco de investigación SNP-1; también se hizo uso de equipo eco-integrador. Se discuten las fuentes de errores sistemáticos existentes en ese trabajo. Se llega a la conclusión que lo que ese trabajo indicó fue que en Febrero de 1973 existía alrededor de 4 millones de toneladas de anchoveta.

Relevância:

70.00% 70.00%

Publicador:

Resumo:

This thesis entitled Systematics,life history traits ,abundance and stock assessment of cobia rachycentron canadum (linnaeus ,1766) occurring in indian waters with special reference to the northwest coast of india.Cobia, Rachycentron canadum is a fast growing pelagic fish belonging to the monotypic family Rachycentridae. They show worldwide distribution in tropical and sub tropical waters. Cobia is exploited commercially in various countries like Taiwan, Pakistan, India, United State of America, Australia, Gulf of Mexico and the Caribbean. Recreational fishery of Cobia exists in different parts of the world. In India Cobia is caught as bycatch of trawlers, gillnet and hook and line fishery.This study also focuses on to bring out the distribution pattern and also to assess the biomass and estimate sustainable yield of Cobia inhabiting in Indian EEZ. In addition to above, present study standardised live collection methods and also reviewed culture prospects.Results of osteological study and morphological studies indicate its close resemblance to Remora and support the view that Cobia was evolved from Dolphin fishes and remoras followed it. Study also confirmed that Cobia does not have any relative or similar species and is a monotypic species belonging to the family Rachycentridae. Re description of the species was done based on the characters identified. In this study, feeding intensity was also assessed following methods like Gastrosomatic index, Mean index of feeding intensity and Index of fullness. Sex wise, month wise and length group wise fluctuations in the feeding intensity also were studied. Cobia actively fed during post monsoon period. In general, adult fed actively than the juveniles. Trophic level value estimated (4.36) indicates that Cobia occupy top level position in the food chain.

Relevância:

70.00% 70.00%

Publicador:

Resumo:

Location or stock-specific landing data are necessary to improve management of shark stocks, especially those imperiled by overexploitation as a result of the international shark fin trade. In the current absence of catch monitoring directly at extraction sites, genetic stock identification of fins collected from major market supply chain endpoints offers an overlooked but potentially useful approach for tracing the fins back to their geographical, or stock of, origin. To demonstrate the feasibility of this approach, we used mitochondrial control region (mtCR) sequences to trace the broad geographical origin of 62 Hong Kong market-derived Sphyrna lewini fins. Of these fins 21% were derived from the western Atlantic, where this species is listed as 'Endangered' by the International Union for the Conservation of Nature (IUCN). We also show that S. lewini mtCR sequences are geographically segregated in the western Atlantic (overall ΦST = 0.74, n = 177 sharks), indicating that breeding females either remain close to, or home back to, their natal region for parturition. Mixed stock analysis simulations showed that it is possible to estimate the relative contributions of these mitochondrial stocks to fin mixtures in globally sourced trade hubs. These findings underscore the feasibility of using genetic stock identification to source market-derived shark fins to obtain essential and otherwise unavailable data on exploitation levels, and thus to productively inform stock assessment and management of S. lewini and potentially also of other fished shark species. © Inter-Research 2009.

Relevância:

70.00% 70.00%

Publicador:

Resumo:

Under the 1994 amendments to the Marine Mammal Protection Act (MMPA), the National Marine Fisheries Service (NMFS) and the U.S. Fish and Wildlife Service (USFWS) are required to publish Stock Assessment Reports for all stocks of marine mammals within U.S. waters, to review new information every year for strategic stocks and every three years for non-strategic stocks, and to update the stock assessment reports when significant new information becomes available. This report presents stock assessments for 13 Pacific marine mammal stocks under NMFS jurisdiction, including 8 “strategic” stocks and 5 “non-strategic” stocks (see summary table). A new stock assessment for humpback whales in American Samoa waters is included in the Pacific reports for the first time. New or revised abundance estimates are available for 9 stocks, including Eastern North Pacific blue whales, American Samoa humpback whales, five U.S. west coast harbor porpoise stocks, the Hawaiian monk seal, and southern resident killer whales. A change in the abundance estimate of Eastern North Pacific blue whales reflects a recommendation from the Pacific Scientific Review Group to utilize mark-recapture estimates for this population, which provide a better estimate of total population size than the average of recent line-transect and mark-recapture estimates. The ‘Northern Oregon/Washington Coast Stock’ harbor porpoise stock assessment includes a name change (‘Oregon’ is appended to ‘Northern Oregon’) to reflect recent stock boundary changes. Changes in abundance estimates for the two stocks of harbor porpoise that occur in Oregon waters are the result of these boundary changes, and do not reflect biological changes in the populations. Updated information on the three stocks of false killer whales in Hawaiian waters is also included in these reports. Information on the remaining 50 Pacific region stocks will be reprinted without revision in the final 2009 reports and currently appears in the 2008 reports (Carretta et al. 2009). Stock Assessments for Alaskan marine mammals are published by the National Marine Mammal Laboratory (NMML) in a separate report. Pacific region stock assessments include those studied by the Southwest Fisheries Science Center (SWFSC, La Jolla, California), the Pacific Islands Fisheries Science Center (PIFSC, Honolulu, Hawaii), the National Marine Mammal Laboratory (NMML, Seattle, Washington), and the Northwest Fisheries Science Center (NWFSC, Seattle, WA). Northwest Fisheries Science Center staff prepared the report on the Eastern North Pacific Southern Resident killer whale. National Marine Mammal Laboratory staff prepared the Northern Oregon/Washington coast harbor porpoise stock assessment. Pacific Islands Fisheries Science Center staff prepared the report on the Hawaiian monk seal. Southwest Fisheries Science Center staff prepared stock assessments for 9 stocks. The stock assessment for the American Samoa humpback whale was prepared by staff from the Center for Coastal Studies, Hawaiian Islands Humpback National Marine Sanctuary, the Smithsonian Institution, and the Southwest Fisheries Science Center. Draft versions of the stock assessment reports were reviewed by the Pacific Scientific Review Group at the November 2008, Maui meeting. The authors also wish to thank those who provided unpublished data, especially Robin Baird and Joseph Mobley, who provided valuable information on Hawaiian cetaceans. Any omissions or errors are the sole responsibility of the authors. This is a working document and individual stock assessment reports will be updated as new information on marine mammal stocks and fisheries becomes available. Background information and guidelines for preparing stock assessment reports are reviewed in Wade and Angliss (1997). The authors solicit any new information or comments which would improve future stock assessment reports. These Stock Assessment Reports summarize information from a wide range of sources and an extensive bibliography of all sources is given in each report. We strongly urge users of this document to refer to and cite original literature sources rather than citing this report or previous Stock Assessment Reports. If the original sources are not accessible, the citation should follow the format: [Original source], as cited in [this Stock Assessment Report citation].

Relevância:

70.00% 70.00%

Publicador:

Resumo:

Under the 1994 amendments to the Marine Mammal Protection Act, the National Marine Fisheries Service (NMFS) and the U.S. Fish and Wildlife Service (USFWS) were required to produce stock assessment reports for all marine mammal stocks in waters within the U.S. Exclusive Economic Zone. This document contains the stock assessment reports for the U.S. Pacific marine mammal stocks under NMFS jurisdiction. Marine mammal species which are under the management jurisdiction of the USFWS are not included in this report. A separate report containing background, guidelines for preparation, and .a summary of all stock assessment reports is available from the NMFS Office of Protected Resources. This report was prepared by staff of the Southwest Fisheries Science Center, NMFS and the Alaska Fisheries Science Center, NMFS. The information presented here was compiled primarily from published sources, but additional unpublished information was included where it contributed to the assessments. The authors wish to thanks the members of the Pacific Scientific Review Group for their valuable contributions and constructive criticism: Hannah Bernard, Robin Brown, Mark Fraker, Doyle Hanan, John Heyning, Steve Jeffries, Katherine Ralls, Michael Scott, and Terry Wright. Their comments greatly improved the quality of these reports, We also thanks the Marine Mammal Commission, The Humane Society of the United States, The Marine Mammal Center, The Center for Marine Conservation, and Friends of the Sea Otter for their careful reviews and thoughtful comments. Special thanks to Paul Wade of the Office of Protected Resources for his exhaustive review and comments, which greatly enhanced the consistency and technical quality of the reports. Any ommissions or errors are the sole responsibility of the authors. This is a working document and individual stock assessment reports will be updated as new information becomes available and as changes to marine mammal stocks and fisheries occur; therefore, each stock assessment report is intended to be a stand alone document. The authors solicit any new information or comments which would improve future stock assessment reports. This is Southwest Fisheries Science Center Technical Memorandum NOAA-TM-NMFS-SWFSC- 219, July 1995. 111

Relevância:

70.00% 70.00%

Publicador:

Resumo:

Il presente studio si occupa di indagare lo stato delle popolazioni di alici, Engraulis encrasicolus, e sardine, Sardina pilchardus, presenti nel Mar Adriatico Centrale e Settentrionale attraverso l’utilizzo di metodi di dinamica di popolazione. L’attenzione per queste specie è dovuta alla loro importanza commerciale; sono, infatti, specie “target” della flotta peschereccia italiana, in particolare nell’area adriatica. I metodi di dinamica di popolazione sono uno degli aspetti più importanti delle scienze della pesca. Attraverso lo stock assessment si possono acquisire informazioni sull’abbondanza in mare delle risorse nel tempo e nello spazio, nonché sulla mortalità dovuta all’attività di pesca, che sono di primaria importanza per l’adozione di misure gestionali. I metodi di dinamica di popolazione esaminati e confrontati in questa tesi sono stati due: Virtual Population Analysis (VPA) e Integrated Catch-at-Age Analysis (ICA). Prima, però, è stato necessario esaminare le modalità con cui ottenere i dati di “input”, quali: tassi di crescita delle specie, mortalità naturale, sforzo di pesca, dati di cattura. Infine, è stato possibile ricostruire nel tempo la storia dello stock in questione e il suo stato attuale, dando indicazioni per lo sfruttamento futuro in un’ottica di conservazione dello stock stesso. Attraverso la determinazione della curva di crescita si sono potuti ottenere i parametri di crescita delle specie in esame, necessari per definire i tassi di mortalità naturale. L’abbondanza di questi stock è stata valutata con i programmi Age Length Key (ALK) e Iterative Age Length Key (IALK). Nei programmi di stock assessment utilizzati si è preferito utilizzare la stima di abbondanza calcolata con il primo metodo, in quanto più rappresentativo dello stock in esame. Un parametro di fondamentale importanza e di difficile stima è la mortalità; in particolare, in questo studio ci siamo occupati di determinare la mortalità naturale. Questa è stata determinata utilizzando due programmi: ProdBiom (Abella et al., 1998) e il sistema ideato da Gislason et al. (2008). Nonostante l’approccio conservativo suggerisca l’utilizzo dei valori ricavati da ProdBiom, in quanto più bassi, si è preferito utilizzare i tassi di mortalità naturale ricavati dalla seconda procedura. Questa preferenza è stata determinata dal fatto che il programma ProdBiom consegna indici di mortalità naturale troppo bassi, se confrontati con quelli presentati in letteratura per le specie in esame. Inoltre, benché nessuno dei due programmi sia stato costruito appositamente per le specie pelagiche, è comunque preferibile la metodologia ideata da Gislason et al. (2008), in quanto ottenuta da un esame di 367 pubblicazioni, in alcune delle quali erano presenti dati per queste specie. Per quanto riguarda i dati di cattura utilizzati in questo lavoro per il calcolo della Catch Per Unit Effort (CPUE, cioè le catture per unità di sforzo), si sono utilizzati quelli della marineria di Porto Garibaldi, in quanto questa vanta una lunga serie temporale di dati, dal 1975 ad oggi. Inoltre, in questa marineria si è sempre pescato senza imposizione di quote e con quantitativi elevati. Determinati questi dati è stato possibile applicare i programmi di valutazione degli stock ittici: VPA e ICA. L’ICA risulta essere più attendibile, soprattutto per gli anni recenti, in quanto prevede un periodo nel quale la selettività è mantenuta costante, riducendo i calcoli da fare e, di conseguenza, diminuendo gli errori. In particolare, l’ICA effettua i suoi calcoli considerando che i dati di cattura e gli indici di “tuning” possono contenere degli errori. Nonostante le varie differenze dei programmi e le loro caratteristiche, entrambi concordano sullo stato degli stock in mare. Per quanto riguarda l’alice, lo stock di questa specie nel Mar Adriatico Settentrionale e Centrale, altamente sfruttato in passato, oggi risulta moderatamente sfruttato in quanto il livello di sfruttamento viene ottenuto con un basso livello di sforzo di pesca. Si raccomanda, comunque, di non incrementare lo sforzo di pesca, in modo da non determinare nuove drastiche diminuzioni dello stock con pesanti conseguenze per l’attività di pesca. Le sardine, invece, presentano un trend diverso: dalla metà degli anni ottanta lo stock di Sardina pilchardus ha conosciuto un continuo e progressivo declino, che solo nell’ultimo decennio mostra un’inversione di tendenza. Questo, però, non deve incoraggiare ad aumentare lo pressione di pesca, anzi bisogna cercare di mantenere costante lo sforzo di pesca al livello attuale in modo da permettere il completo ristabilimento dello stock (le catture della flotta italiana sono, infatti, ancora relativamente basse). Questo lavoro, nonostante i vari aspetti da implementare (quali: il campionamento, le metodologie utilizzate, l’introduzione di aspetti non considerati, come ad es. gli scarti,… etc.) e le difficoltà incontrate nel suo svolgimento, ha fornito un contributo di approfondimento sugli spinosi aspetti della definizione del tasso di mortalità naturale, individuando una procedura più adatta per stimare questo parametro. Inoltre, ha presentato l’innovativo aspetto del confronto tra i programmi ICA e VPA, mostrando una buon accordo dei risultati ottenuti. E’ necessario, comunque, continuare ad approfondire questi aspetti per ottenere valutazioni sempre più precise e affidabili, per raggiungere una corretta gestione dell’attività di pesca e ai fini della preservazione degli stock stessi.

Relevância:

70.00% 70.00%

Publicador:

Resumo:

The development of the ecosystem approach and models for the management of ocean marine resources requires easy access to standard validated datasets of historical catch data for the main exploited species. They are used to measure the impact of biomass removal by fisheries and to evaluate the models skills, while the use of standard dataset facilitates models inter-comparison. North Atlantic albacore tuna is exploited all year round by longline and in summer and autumn by surface fisheries and fishery statistics compiled by the International Commission for the Conservation of Atlantic Tunas (ICCAT). Catch and effort with geographical coordinates at monthly spatial resolution of 1° or 5° squares were extracted for this species with a careful definition of fisheries and data screening. In total, thirteen fisheries were defined for the period 1956-2010, with fishing gears longline, troll, mid-water trawl and bait fishing. However, the spatialized catch effort data available in ICCAT database represent a fraction of the entire total catch. Length frequencies of catch were also extracted according to the definition of fisheries above for the period 1956-2010 with a quarterly temporal resolution and spatial resolutions varying from 1°x 1° to 10°x 20°. The resolution used to measure the fish also varies with size-bins of 1, 2 or 5 cm (Fork Length). The screening of data allowed detecting inconsistencies with a relatively large number of samples larger than 150 cm while all studies on the growth of albacore suggest that fish rarely grow up over 130 cm. Therefore, a threshold value of 130 cm has been arbitrarily fixed and all length frequency data above this value removed from the original data set.

Relevância:

70.00% 70.00%

Publicador:

Resumo:

The development of the ecosystem approach and models for the management of ocean marine resources requires easy access to standard validated datasets of historical catch data for the main exploited species. They are used to measure the impact of biomass removal by fisheries and to evaluate the models skills, while the use of standard dataset facilitates models inter-comparison. North Atlantic albacore tuna is exploited all year round by longline and in summer and autumn by surface fisheries and fishery statistics compiled by the International Commission for the Conservation of Atlantic Tunas (ICCAT). Catch and effort with geographical coordinates at monthly spatial resolution of 1° or 5° squares were extracted for this species with a careful definition of fisheries and data screening. In total, thirteen fisheries were defined for the period 1956-2010, with fishing gears longline, troll, mid-water trawl and bait fishing. However, the spatialized catch effort data available in ICCAT database represent a fraction of the entire total catch. Length frequencies of catch were also extracted according to the definition of fisheries above for the period 1956-2010 with a quarterly temporal resolution and spatial resolutions varying from 1°x 1° to 10°x 20°. The resolution used to measure the fish also varies with size-bins of 1, 2 or 5 cm (Fork Length). The screening of data allowed detecting inconsistencies with a relatively large number of samples larger than 150 cm while all studies on the growth of albacore suggest that fish rarely grow up over 130 cm. Therefore, a threshold value of 130 cm has been arbitrarily fixed and all length frequency data above this value removed from the original data set.

Relevância:

70.00% 70.00%

Publicador:

Resumo:

The development of the ecosystem approach and models for the management of ocean marine resources requires easy access to standard validated datasets of historical catch data for the main exploited species. They are used to measure the impact of biomass removal by fisheries and to evaluate the models skills, while the use of standard dataset facilitates models inter-comparison. North Atlantic albacore tuna is exploited all year round by longline and in summer and autumn by surface fisheries and fishery statistics compiled by the International Commission for the Conservation of Atlantic Tunas (ICCAT). Catch and effort with geographical coordinates at monthly spatial resolution of 1° or 5° squares were extracted for this species with a careful definition of fisheries and data screening. In total, thirteen fisheries were defined for the period 1956-2010, with fishing gears longline, troll, mid-water trawl and bait fishing. However, the spatialized catch effort data available in ICCAT database represent a fraction of the entire total catch. Length frequencies of catch were also extracted according to the definition of fisheries above for the period 1956-2010 with a quarterly temporal resolution and spatial resolutions varying from 1°x 1° to 10°x 20°. The resolution used to measure the fish also varies with size-bins of 1, 2 or 5 cm (Fork Length). The screening of data allowed detecting inconsistencies with a relatively large number of samples larger than 150 cm while all studies on the growth of albacore suggest that fish rarely grow up over 130 cm. Therefore, a threshold value of 130 cm has been arbitrarily fixed and all length frequency data above this value removed from the original data set.

Relevância:

70.00% 70.00%

Publicador:

Resumo:

The development of the ecosystem approach and models for the management of ocean marine resources requires easy access to standard validated datasets of historical catch data for the main exploited species. They are used to measure the impact of biomass removal by fisheries and to evaluate the models skills, while the use of standard dataset facilitates models inter-comparison. North Atlantic albacore tuna is exploited all year round by longline and in summer and autumn by surface fisheries and fishery statistics compiled by the International Commission for the Conservation of Atlantic Tunas (ICCAT). Catch and effort with geographical coordinates at monthly spatial resolution of 1° or 5° squares were extracted for this species with a careful definition of fisheries and data screening. In total, thirteen fisheries were defined for the period 1956-2010, with fishing gears longline, troll, mid-water trawl and bait fishing. However, the spatialized catch effort data available in ICCAT database represent a fraction of the entire total catch. Length frequencies of catch were also extracted according to the definition of fisheries above for the period 1956-2010 with a quarterly temporal resolution and spatial resolutions varying from 1°x 1° to 10°x 20°. The resolution used to measure the fish also varies with size-bins of 1, 2 or 5 cm (Fork Length). The screening of data allowed detecting inconsistencies with a relatively large number of samples larger than 150 cm while all studies on the growth of albacore suggest that fish rarely grow up over 130 cm. Therefore, a threshold value of 130 cm has been arbitrarily fixed and all length frequency data above this value removed from the original data set.

Relevância:

70.00% 70.00%

Publicador:

Resumo:

The development of the ecosystem approach and models for the management of ocean marine resources requires easy access to standard validated datasets of historical catch data for the main exploited species. They are used to measure the impact of biomass removal by fisheries and to evaluate the models skills, while the use of standard dataset facilitates models inter-comparison. North Atlantic albacore tuna is exploited all year round by longline and in summer and autumn by surface fisheries and fishery statistics compiled by the International Commission for the Conservation of Atlantic Tunas (ICCAT). Catch and effort with geographical coordinates at monthly spatial resolution of 1° or 5° squares were extracted for this species with a careful definition of fisheries and data screening. In total, thirteen fisheries were defined for the period 1956-2010, with fishing gears longline, troll, mid-water trawl and bait fishing. However, the spatialized catch effort data available in ICCAT database represent a fraction of the entire total catch. Length frequencies of catch were also extracted according to the definition of fisheries above for the period 1956-2010 with a quarterly temporal resolution and spatial resolutions varying from 1°x 1° to 10°x 20°. The resolution used to measure the fish also varies with size-bins of 1, 2 or 5 cm (Fork Length). The screening of data allowed detecting inconsistencies with a relatively large number of samples larger than 150 cm while all studies on the growth of albacore suggest that fish rarely grow up over 130 cm. Therefore, a threshold value of 130 cm has been arbitrarily fixed and all length frequency data above this value removed from the original data set.