Salmon action plan. River Ribble - August 2000

In February 1996 A Strategy for the Management of Salmon in England and Wales was launched by the National Rivers Authority. The strategy concentrates on four main objectives for the management of salmon fisheries in England and Wales: (i) Optimise the number of salmon returning to home water fisheries, (ii) Maintain and improve the fitness and diversity of salmon stocks, (iii) Optimise the total economic value of surplus stocks, (iv) Ensure necessary costs are met by beneficiaries. These four objectives will be addressed through local Salmon Action Plans (SAPs) which will be produced for each of the principle salmon rivers in England and Wales by the year 2001. This Salmon Action Plan for the River Ribble reviews the status of the stock and the fisheries, seeks to identify the main factors limiting performance, to draw up and cost a list of options to address these, and to consult with local interest groups.

River Kent salmon action plan - consultation draft

In February 1996, the National Salmon Management Strategy was launched by the Environment Agency's predecessor the National Rivers Authority (NRA, 1996). The strategy concentrates on four main objectives for the management of salmon fisheries in England and Wales. These are primarily aimed at securing the well being of the stock, but in doing so will improve catches and the associated economic returns to the fisheries. The four main objectives are : (i) Optimise the number of salmon returning to home water fisheries, (ii) Maintain and improve fitness and diversity of salmon stocks. (Hi) Optimise the total economic value of surplus stocks, (iv) Ensure necessary costs are met by beneficiaries

Multiple stable reference points in oyster populations: implications for reference point-based management

In the second of two companion articles, a 54-year time series for the oyster population in the New Jersey waters of Delaware Bay is analyzed to examine how the presence of multiple stable states affects reference-point–based management. Multiple stable states are described by four types of reference points. Type I is the carrying capacity for the stable state: each has associated with it a type-II reference point wherein surplus production reaches a local maximum. Type-II reference points are separated by an intermediate surplus production low (type III). Two stable states establish a type-IV reference point, a point-of-no-return that impedes recovery to the higher stable state. The type-II to type-III differential in surplus production is a measure of the difficulty of rebuilding the population and the sensitivity of the population to collapse at high abundance. Surplus production projections show that the abundances defining the four types of reference points are relatively stable over a wide range of uncertainties in recruitment and mortality rates. The surplus production values associated with type-II and type-III reference points are much more uncertain. Thus, biomass goals are more easily established than fishing mortality rates for oyster population

A production modeling approach to the assessment of the horseshoe crab (Limulus polyphemus) population in Delaware Bay

Horseshoe crab (Limulus polyphemus) is harvested commercially, used by the biomedical industry, and provides food for migrating shorebirds, particularly in Delaware Bay. Recently, decreasing crab population trends in this region have raised concerns that the stock may be insufficient to fulfill the needs of these diverse user groups. To assess the Delaware Bay horseshoe crab population, we used surplus production models (programmed in ASPIC), which incorporated data from fishery-independent surveys, fishery-dependent catch-per-unit-of-effort data, and regional harvest. Results showed a depleted population (B2003/=0.03−0.71) BMSY and high relative fishing mortality /FMSY=0.9−9.5). Future harvest (F2002strategies for a 15-year period were evaluated by using population projections with ASPICP software. Under 2003 harvest levels (1356 t), population recovery to BMSY would take at least four years, and four of the seven models predicted that the population would not reach BMSY within the 15year period. Production models for horseshoe crab assessment provided management benchmarks for a species with limited data and no prior stock assessment

Estimating the maximum sustainable yield of bonito (Sarda chiliensis, Scombridae) of northern Chile from monthly catch data

Monthly catch data of bonito Sarda chiliensis from northern Chile, from 1976 to 1989, were used to obtain a series of estimates of the Z-G parameter (i.e., total mortality minus the growth coefficient in weight). This series was then used to estimate a maximum sustainable yield of 4,500 t/year through a modified version of the surplus production model of J. Csirke and J. Caddy. The status of the fishery is discussed.

Aspects of phosphorus pollution from aquaculture

Phosphorus is an essential element for living organisms and exists in waterbodies as dissolved and particulate forms. Phosphorus is required for optimum growth, feed efficiency, bone development and maintenance of acid-base regulation in fish. The presence of high concentration of phosphates in water may indicate presence of pollution as it may accelerate plant growth and disrupt the aquatic ecosystem thereby benefiting certain species and altering species diversity in affected areas. Eutrophication of waterbodies is often correlated with the phosphorus loading into the environment and aquaculture has been identified as one of the sources of phosphorus pollution. Details of the impacts of eutrophication is given in Bernhardt (1981). Phosphorus must be provided in fish feed because of its low concentration in water. Studies made in Europe and Northern America have revealed a phosphorus surplus in most commercial feeds which is above actual requirements; or is supplied in a form which is unavailable to the fish. Surplus phosphorus is excreted, while unavailable phosphorus is passed out in the feces. Discharge of phosphorus from fish farms and hatchery effluents have caused phosphorus pollution in Nordic countries, North America and Europe. This article examines the path of phosphorus pollution, quantification/prediction of phosphorus load from aquaculture and remedial measures.

Estimation of deepwater snapper yield from Tongan seamounts

The data from two years' monitoring of the Tongan seamount fishery were analyzed the two main export species are Pristipomoides filamentosus and Etelis coruscans. K.R. Allen's model was used to obtain estimates of catchability and recruitment and of a surplus production of 737 kg per nautical mile (nm) of 200 m contour. This compared reasonably well to total landings. Using this estimate, the annual surplus production for Tonga's 294 nm of 200 m contour is 217 t. The level of fishing mortality was found to be 0.3/year.

Multiple environmental states affecting penaeid shrimp production in Peru

A modification of the Schaefer surplus-production model was used to account for environmental induced variations of shrimp (Penaeus vannamei) catch in northern Peru. Based on time series of catch, effort, river discharge and sea surface temperature, fluctuations in catch of shrimps are explained and discussed with respect to multiple level of carrying capacity and hence different maximum sustainable yields.

Culture of mola (Amblypharyngodon mola) in polyculture with carps: experience from a field trial in Bangladesh

Studies were carried out during May 1997 to January 1998 in Kishoregani district in Bangladesh to investigate the production potential of carp polyculture in combination with Amblypharyngodon mola in seasonal ponds. The preliminary results indicate that A. mola can be successfully cultured in small seasonal ponds in polyculture with carp. This practice can result in an increase in the households' consumption of small fish which have a very high content of calcium, iron and vitamin A. In addition to the nutritional benefits, it can also provide additional income through sale of carp and surplus small fish.

Escalation in shrimp production in the Sierra Leone industrial fishery

Applying Turkey's jackknife method on MSY estimates from the surplus production models of Schaefer and Fox showed that the optimum yield for shrimps in industrial fishery in Sierra Leone is estimated at 2,686.8 t with 15,822 fishing days. Annual catch for 1996 was 2,788 t, indicating an escalation in exploitation which, if prolonged, could bring reduced productivity as experienced in the fishery some years ago.

Catch-effort relationship in Pacific bigeye tuna fishery

Some problems associated with fitting surplus production models to unsuitable data are discussed. This is illustrated by an application of the Schaefer, Fox and PRODFIT models to Pacific Ocean bigeye tuna (Thunnus obesus ) catch and effort data for 1952-1987, which appear to be better described by purely empirical models.

Size-composition of Annual Landings in the White Shrimp, Litopenaeus setiferus, Fishery of the Northern Gulf of Mexico, 1960–2006: Its Trend and Relationships with Other Fishery-dependent Variable

The potential for growth overfishing in the white shrimp, Litopenaeus setiferus, fishery of the northern Gulf of Mexico appears to have been of limited concern to Federal or state shrimp management entities, following the cataclysmic drop in white shrimp abundance in the 1940’s. As expected from surplus production theory, a decrease in size of shrimp in the annual landings accompanies increasing fishing effort, and can eventually reduce the value of the landings. Growth overfishing can exacerbate such decline in value of the annual landings. We characterize trends in size-composition of annual landings and other annual fishery-dependent variables in this fishery to determine relationships between selected pairs of these variables and to determine whether growth overfishing occurred during 1960–2006. Signs of growth overfishing were equivocal. For example, as nominal fishing effort increased, the initially upward, decelerating trend in annual yield approached a local maximum in the 1980’s. However, an accelerating upward trend in yield followed as effort continued to increase. Yield then reached its highest point in the time series in 2006, as nominal fishing effort declined due to exogenous factors outside the control of shrimp fishery managers. The quadratic relationship between annual yield and nominal fishing effort exhibited a local maximum of 5.24(107) pounds (≈ MSY) at a nominal fishing effort level of 1.38(105) days fished. However, annual yield showed a continuous increase with decrease in size of shrimp in the landings. Annual inflation-adjusted ex-vessel value of the landings peaked in 1989, preceded by a peak in annual inflation-adjusted ex-vessel value per pound (i.e. price) in 1983. Changes in size composition of shrimp landings and their economic effects should be included among guidelines for future management of this white shrimp

An Assessment of Fishery Yields from the East China Sea Ecosystem

A first assessment ofimportant East China Sea fisheries was carried out using data from 1956 to 1993. Two different data sets were available: 1) catch and effort data taken from landings and boat registrations and 2) catch and effort data from skipper's logs taken at sea. The two sets provided similar trends in CPUE over the study period. Stocks of high value, low volume species have been fished heavily and now produce very low landings or have been depleted (e.g. small and large yellow croaker). Some high volume and low value species have also been heavily fished (e.g. green filefish) while others (e.g. hairtail) are still producing high landings. Surplus production models were fitted to seven stocks. All showed considerable fluctuations in landings around MSY. The green filefish stock had an estimated MSY of around 160,000 tlyr at an effort of 2,500,000 kw and was depleted by a combination of excessive effort (around 4,000,000 kw in 1993) and marked fluctuations in landings (up to 70,000 tlyr above or below MSY). A sustainable policyfor managing ECS fisheries should address the effects ofboth effort and environmental variation.

A Social and Economic Characterization of the U.S. Gulf of Mexico Recreational Shark Fishery

A mail survey of tournament shark anglers and party boat shark anglers was completed to examine their fishing activity, attitudes, trip expenditures, and consumer surplus. A sample of 700 shark anglers was selected from tournaments in the Gulf of Mexico during 1990, and a sample of party boat shark anglers was drawn from Port Aransas, Tex., party boat anglers during the summer of 1991. A response rate of 58% (excluding nondeliverables) was obtained from tournament anglers. The sample of party boat shark anglers was too small to provide useful results. Tournament shark anglers reported fishing an average of 58 days per year and targeted sharks and other large marine species. Tournaments occupy a small portion of their fishing effort. If this group of anglers were not able to fish for sharks, one-third indicated no other species would be an acceptable substitute, while others were willing to substitute other large marine species. Shark trip expenditures averaged $197 per trip with a consumer surplus of $111 per trip. Based on MRFSS estimates of the number of shark fishing trips, we estimate a total of $43,355,000 was spent by shark anglers in the Gulf of Mexico with a consumer surplus of $23,865,000 for a total gross value of the shark fishery of $66,220,000. MRFSS estimates of the number of sharks landed indicate an equivalent use value of $183 per shark.

Characteristics of Billfish Anglers in the U.S. Atlantic Ocean

A mail survey of 1,984 U.S. billfish tournament anglers was completed to examine their fishing activity, attitudes, trip expenditures, consumer's surplus, catch levels, and management preferences. A sample of 1,984 anglers was drawn from billfish tournaments in the western Atlantic Ocean (from Maine to Texas, including Puerto Rico and the U.S. Virgin Islands) during 1989. A response rate of 61% was obtained (excluding nondeliverables). Anglers averaged 13 billfish trips per year, catching a billfish 40% of the time while 89% of billfish caught were released with <1 billfish per year per angler retained. Catch and retention rates varied by region. Expenditures averaged $1,600 per trip, but varied by region. The annual consumer's surplus was $262 per angler, but increased to $448 per angler if billfish populations were to increase. An estimated 7,915 tournament anglers in the U.S. western Atlantic spent $179,425,000 in pursuit of billfish in 1989. Anglers opposed management options that would diminish their ability to catch a billfish, but supported options limiting the number of billfish landed.