[What's in the Naga] [Why Naga] [Who gets the Naga] [Publish in the Naga] [Advertise in the Naga]

The ICLARM Quarterly
October - December 1999, Vol. 22, No. 4

Four Blocks to Controlling Fishing Pressure

The world's fish stocks are under heavy fishing pressure from both large and small scale fishers. Their productivity can only be restored if this pressure is reduced. Yet, this apparently simple prescription is very difficult to follow.

Why is it so hard to reduce fishing pressure and where do the solutions lie?
Four major factors hinder efforts to reduce fishing pressure: economic dependency; political advocacy; uncertainty about the status of the resource; and lack of adequate management measures. The sum of these factors and their interdependence make for a powerful resistance to reduction in fishing pressure.
Owners of fishing gear, from large commercial fleets fishing in the oceans to small individual fishers fishing in inland and nearshore waters, are directly dependent on fisheries. So are a large numbers of wage laborers in fishing and related activities as well as fish sellers. Any reduction in fishing will have an immediate and direct impact on their incomes, especially where there are few alternative economic opportunities. Creating viable alternatives can remove this limitation. For example, fishers in San Salvador Island, Philippines, were dependent on blast fishing for their livelihoods, despite its risks and dangers. A community-based program helped stop this practice and designated part of the island into a protected area. When this was combined with a program to help the fishers capture reef fish for the live aquarium trade using better methods, the economic dependence on the former destructive fishing practices vanished, fishing pressure was reduced, the resource condition improved and the livelihoods of the fishers improved with new markets.

Political activism is a block that often results from conflict over rights to scarce resources. Often, powerful commercial interests vie for the same resources as small fishers. This distorts or delays policy decisions, especially when the third factor comes into play - uncertainty. How much does the fishing pressure need to be reduced, for how long, and will it achieve the desired results? Where time and financial resources prevent full scale resource assessment, rapid and participatory assessment methods using local knowledge can be very useful in clarifying the parameters and suggesting solutions. Providing the policymakers and managers with knowledge about fisheries and the tools to assess them can help them withstand pressures and make well-informed decisions.

Both traditional and modern management regimes lack the necessary control mechanisms. Here it is necessary to look at the issue of access rights, the true public value of the resources, how to improve compliance and, most important, involve local communities in the planning and implementation of resource management systems.

Although the four constraints are formidable, they can be surmounted if programs are established to create alternative economic activities, inform and support politicians and administrators, provide effective assessment tools, and improve the levers of control for the management of fisheries. Sooner or later, the issues of fishing rights must be addressed. The prescription is not simple but the stakes are high – fisheries must be made more sustainable and this almost always means controlling the fishing pressure.


Culture of Tropical Sea Cucumbers for Stock Restoration and Enhancement
S.C. Battaglene


Severe overfishing of sea cucumbers has occurred in most countries of the tropical Indo-Pacific. The release of cultured juveniles is being examined at the ICLARM Coastal Aquaculture Centre (CAC) in the Solomon Islands as a means of restoring and enhancing tropical sea cucumber stocks. Sandfish (Holothuria scabra) are the tropical species that show the best potential for stock enhancement. Sandfish are of high value, widely distributed and relatively easy to culture in simple systems at a low cost. This paper summarizes information about the culture of H. scabra and compares it to that of the temperate species Stichopus japonicus. Sandfish live in high nutrient environments at densities of 100s per ha. They have a reproductive peak in September and October, but can be induced to spawn throughout the year. Increases in water temperature and addition of powdered algae are effective ways of inducing spawning. Chaetoceros muelleri and Rhodomonas salina are two of the better microalgae for feeding the larvae. Sandfish larvae are more robust and easier to rear than those of other tropical species. Larvae metamorphose into juveniles after two weeks at 28°C and settle on diatom conditioned plates. The CAC has produced over 200 000 juveniles from six separate spawnings. Sandfish can be reared on hard substrata until they reach 20 mm in length and are then best transferred to sand substrata. Absolute daily growth rates for juvenile sandfish average 0.5 mm day -1 (±0.03 s.e.) and range from 0.2 to 0.8 mm day -1, depending on stocking density, light intensity and addition of powdered algae. Overall, there are good reasons to believe that sandfish can be produced cost-effectively for restocking and stock enhancement. The potential for using cultured juveniles to manage fisheries for sea cucumbers now depends on the development of strategies to optimize the survival of juveniles released into the wild and to evaluate  releases on a commercial scale.

S.C. Battaglene is with the International Center for Living Aquatic Resources Management (ICLARM), Coastal Aquaculture Centre (CAC), PO Box 438, Honiara, Solomon Islands.

Hatchery and Culture Technology for the Sea Cucumber, Holothuria scabra Jaeger, in India
D.B. James


The seed of the sea cucumber Holothuria scabra Jaeger is being produced at the Central Marine Fisheries Research Institute in India. This article describes the techniques being used in the production of the seed and the experiments being carried out for the rearing of juveniles. Trials to grow juveniles in hatcheries on prawn farms have shown spectacular results that are both cost efficient and environmentally friendly.

D.B. James is a Senior Scientist at the Research Centre of the Central Marine Fisheries Research Institute, Tuticorin-628 001, Cochin, India.

Volunteer Sports Divers: A Valuable Resource in the Management of Bahrain’s Fisheries
K.R. Uwate and J. Al-Meshkhas


The Directorate of Fisheries (DOF) of Bahrain has a novel scheme in which the DOF workers cooperate with local sports divers in the management and conservation of their marine resources. This cooperation is mutually beneficial for both the DOF and the divers who are interested in environmental conservation.

K.R. Uwate is currently the Advisor to the Director of Fisheries, Bahrain. He coordinates volunteer dive trips for the DOF while J. Al-Meshkhas is an Officer of the Bahrain Diving Committee and coordinates volunteer divers for this joint project.

Network of Tropical Aquaculture Fisheries Professionals (NTAFP) Section

Aquabyte (Aquaculture Section of NTAFP)

Brush Shelter: A Recently Introduced Fishing Method in the Kaptai Reservoir Fisheries in Bangladesh
K.K. Ahmed and J.B. Hambrey


Since the early 1990s, the brush shelter fish aggregation device (FAD), an unusual fishing method used in Bangladesh, has become popular with the fishers of Kaptai Lake. A shelter commonly covers an area between 0.02 and 0.12 ha and is usually installed along the edge of a channel (arm of lake) with a reasonable water depth. Brushes are square/rectangular/round surrounded with bamboo or wooden frames constructed with tree branches. To attract fish, water hyacinth is placed over the surface. The difference between this fishing practice and similar ones used elsewhere in Bangladesh is that it makes use of locally available feed ingredients (rice bran, wheat bran, mustard oil cake, fermented rice, etc.). Spices and fish scents are also used two to three days prior to harvest. It is estimated that about 1000 brush shelters are in operation around the reservoir and are fished twice a year. The quantity of fish caught in each brush varies directly with the size and location of the brush and feed quality. A total of 483 t of fish of different species is harvested annually, accounting for about 8% of the total catch from the reservoir. Unplanned and unregulated use of this type of fishing poses a serious threat both to the natural stocks and to the effectiveness of stock enhancement as mostly small fish are harvested.

K.K. Ahmed is from the Bangladesh Fisheries Research Institute Riverine Sub-station, PO Box-8, Rangamati-4500, Bangladesh. J.B. Hambrey is from the Aquaculture and Aquatic Resources Management Program, School of Environment, Resources and Development, Asian Institute of Technology, Bangkok, Thailand.

Broodstock Management Status and Some Suggestions to Control Negative Selection and Inbreeding in Hatchery Stocks in Bangladesh
M.G. Hussain and M.A. Mazid


The freshwater river systems and floodplains of Bangladesh are the breeding grounds for 13 endemic species of carps and barbs and a large number of other fish species, including a number of exotic carps and other species that have been introduced for aquaculture. Since 1967, breeding of endemic and exotic aquaculture species for seed production through hypophysation techniques has become a common practice. Over 700 hatcheries established in the private and public sectors have been breeding 13 endemic and 13 exotic fish species and contributing more than 98% (about 117 000 kg) of the total spawn (hatchery) production. Stock deterioration in hatchery populations due to poor broodstock management and inbreeding depression has been observed. Retarded growth, poor reproductive performance, morphological deformities, increased incidence of disease and mortality of hatchery-produced seeds have been reported. The widespread stocking of such genetically poor quality fish seed in closed and open waterbodies is causing concern. In this situation, there is an obvious need to adopt proper broodstock management strategies and breeding plans for commercially important fish species.
The paper describes the present status of broodstock management, identifies problems, and suggests some guidelines to control negative selection and inbreeding in hatchery stocks in Bangladesh.

M.G. Hussain and M.A. Mazid are from the Bangladesh Fisheries Research Institute, Mymensingh 2201, Bangladesh. 

Fishbyte (Fisheries Section of NTAFP)

The von Bertalanffy Growth Curve: When a Good Fit is not Good Enough
P.C. Craig


The von Bertalanffy growth function (VBGF) is used for length based analyses of growth and mortality patterns for management of fisheries. However, certain fish have growth patterns that the VBGF may not be able to describe adequately, e.g., the Acanthurus lineatus in Samoa. In such cases a two-phase VBGF may be a useful approach.

P.C. Craig is a Fish Biologist. Box 532, Klamath, California 95548 USA.

An Overview of Goby-Fry Fisheries
K.N.I. Bell


A number of diadromous gobies, notably Sicydium spp. and Sicyopterus spp., support fisheries based on return migrations of postlarvae (fry) to rivers. Most species are tropical, although close relatives occur in Japan. The life-history of this group has often been incorrectly described as catadromous (spawning in the sea or estuary), whereas anadromous (spawning in rivers) would be more accurate. Among species, postlarvae range in length from 12 to 30 mm. Postlarvae have often been mistakenly described as new species because adult characters are absent. Most fisheries are in areas of volcanic habitat with high rainfall, torrential streams and high rates of disturbance. Even though some fisheries have been large, almost no historical information on yields exists and, at present, catch data are not regularly collected anywhere. This is a major obstacle in monitoring these fisheries, assessing reports of declining yields and relating them to trends in other variables.

K.N.I. Bell is at the J.L.B. Smith Institute Ichthyology, Private Bag 1015, Grahamstown, 6140 South Africa, and Rhodes University. Email: k.bell@ru.ac.za

Length-Weight Relationships of Freshwater Fishes in Greece
P.K. Kleanthidis, A.I. Sinis and K.I. Stergiouor


Length-weight relationships were calculated for nine fish species from Lake Volvi (Macedonia, Hellas), caught with gillnets of five different mesh sizes between October 1995 and October 1996. In addition, length-weight relationships for 24 Greek freshwater fish species and one hybrid were also obtained from the literature. The values of the exponent of the length-weight relationships for all fish species examined ranged between 2.14 and 3.70 (mean = 3.12; SE = 0.032), and the median value was 3.19.

P.K. Kleanthidis, A.I. Sinis and K.I. Stergiou are from the Laboratory of Ichthyology, Department of Zoology, P.O. Box 134, Faculty of Sciences, Aristotle University of Thessaloniki, 54006, Thessaloniki, Hellas.

Length-Weight Relationships of Tuna Baitfish from the Lakshadweep Islands, India
A.K.V. Nasser


The parameters a and b of the length-weight relationship of the form W=aLb were computed for 11 species of baitfish from the pole-and-line fishery at Minicoy and Spratelloides delicatulus from the fishery at Agatti, Bangaram and Perumal Par.

A.K.V. Nasser is from the Minicoy Research Centre of Central Marine Fisheries Research Institute, Minicoy, Lakshadweep 682 559.


Measuring Transaction Costs of Fisheries Co-Management in San Salvador Island, Philippines
K. Kuperan, N.M.R. Abdullah, R.S. Pomeroy, E.L. Genio and A.M. Salamanca


It is generally accepted that co-management systems are most cost-effective than centralized management of natural resources. However, no attempts have been made to empirically verify the transaction costs involved in fisheries co-management. Some estimates of transaction costs of fisheries co-management in San Salvador Island, Philippines, are presented in this paper. These estimates are used to vompare various transaction costs in co-managed and in centrally managed fisheries in San Salvador Island.

K. Kuperan, E.L. Genio and A.M. Salamanca are from ICLARM; N.M.R. Abdullah is from the Department of Natural Resource Economics, Faculty of Economics and Management, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia; and R.S. Pomeroy is with the World Resource Institute, Biological Resources Program, 10 G Street, NE Suite 800, Washington D.C. 20002, USA.