Fish Age and Growth Studies
- Age and growth studies of the wahoo, Acanthocybium solandri from the southern Caribbean (Trinidad and Tobago, Barbados, St. Vincent and St. Lucia).
- Age and growth studies of the Spanish mackerel, Scomberomorus brasiliensis from Trinidad in collaboration with the Fisheries Division, Ministry of Food Production, Land and Marine Affairs.
- Development of a Fish Otolith Reference Collection
- Photographic Atlas of Fish Otoliths from Trinidad and Tobago
The knowledge of age and growth is fundamental to fishery science. The significance of determining age is that it allows fishery scientists to relate their observations to a time frame and estimate biological rates for various species. Ages of individual fish are used to estimate growth rate, age at recruitment, maturity schedules, and age-specific fecundity for a specific species. In addition, the calculation of natural and fishing mortality rates and age-specific sex ratios also require age data.
This time frame may involve estimating the number of years a fish spends in a particular life stage or habitat, or determining the number of years that fishes are available for harvest.
While several methods exist (e.g. mark and recapture length frequency analysis) to determine the age and consequently the growth of individual fish and fish populations, the most robust method involves age determination from hard-parts of fish. These hard-parts include scales, opercular bones, vertebrae, spines and otoliths (ear bones). Ageing using hard-parts is the preferred route for age and growth determination because the resultant age estimates are more accurate and precise than those derived from length frequency analysis.
In the 1980s research on selected fish species was conducted at the IMA on an ad hoc basis. However, in 1995, age and growth research was centralised with the formation of a Fish Age and Growth Laboratory which was established with assistance from a regional fisheries initiative, the CARICOM Fisheries Resource Assessment and Management Program (CRAMP). Under this Program, age and growth information was provided for several commercial species by participating CARICOM countries.
From left to right: Annuli on whole sagitta of the crevalle jack, Caranx hippos, from Trinidad; Daily growth increments on lapillus of the Spanish mackerel, Scomberomorus brasiliensis from Trinidad; Annuli on sectioned sagitta of the Spanish mackerel, Scomberomorus brasiliensis from Trinidad and Annuli on sectioned sagitta of the lane snapper, Lutjanus synagris, from Belize.
Growth bands or rings (similar to growth rings on a tree), often called annuli can be seen on the hard-parts of fish. These growth bands are often formed on an annual basis.
For most fish, otoliths or ear bones have been the most reliable indicators of age of all the hard parts. Otoliths are formed by a process of biomineralization where calcium carbonate is precipitated on a protein matrix. During periods of fast growth, the protein layers are more compact, giving the growth zone an opaque appearance ,whilst during slower growth, these layers are more spaced, resulting in a translucent zone. These two zones comprise an annulus. The deposition of annual growth rings is thought to be partly caused by seasonal changes in the environment and internal factors.
There are 3 pairs of fish otoliths - the sagittae, asterisci and lapilli. The sagittae are more commonly used for determining ages formed on an annular basis whilst the lapillus is used to determine daily increments. Ages can be determined from reading whole or sectioned otoliths.
Fisheries Co-Management Studies: An Investigation of Fisheries Resources, Resource Users and Fisheries Management by Communities to establish a Framework for Co-Management: Ortoire to Guayaguayare, Southeast Coast, Trinidad
This project was designed to identify and characterise the biological, technical and socio-economic attributes of this fisheries system and characterise and translate the views and knowledge of the fisheries system expressed by the fishers, fisheries scientists, managers and other resource users into a co-management framework which would allow stakeholders to address the prevailing problems in the fisheries and move to a more sustainable approach to its management.
The project was part of a larger regional initiative: Community–based Coastal Resource Management (CBCRM) Project funded by the International Development Research Centre of Canada (IDRC).
Collaborating agencies: International Development Research Centre of Canada (IDRC), International Ocean Institute of Costa Rica (IOI-Costa Rica), CARICOM Fisheries Unit of Belize (CFU), Laval University, Canada and the Institute of Marine Affairs.
Participating countries (CBCRM project): Trinidad and Tobago, Jamaica, Belize, Dominica, St Lucia, Venezuela, Panama, Mexico, Guatemala, Cuba and the Dominican Republic. Research methodology for the project included the use of face-to-face interviews guided by questionnaires to capture information on fishing operations, fisher households, and a perception and attitude survey on resource conditions and fisheries management issues. Other research techniques included the use of key informants, focus group meetings, and participatory GIS involving cognitive mapping of fishing grounds, fish resources and boat migration patterns.
In addition, a video is being produced highlighting the fishing activities on the southeast coast of Trinidad and the development of the community-based co-management model used in the project.
(a) Pulling seine in Plaisance (b) Loading monofilament on boat for fishing trip (c) Setting seine boat
(d) Interviewing fisher for video on the fishing industry on the south east coast of Trinidad
(e-f) Co-management framework workshop conducted by the IMA with south east coast fishers in December 2006.
(g-h) Fish landing site at Guayaguayare (i) Young fisher-woman managing her father’s boat seine crew
(j) Women in Fishing Association (WIFA) general meeting (k) One of the fish species, Lutjanus synagris, lane snapper targeted by southeast coast fishers (l) One of the fish species, Scomberomorus cavalla, Kingfish, targeted by southeast coast fishers, Trinidad.
Fisheries and Participatory GIS
As part of the project, An Investigation of Fisheries Resources, Resource users and Fisheries Management by Communities to establish a Framework for Co-Management: Ortoire to Guayaguayare, Southeast Coast, Trinidad, cognitive mapping of fishing areas based on gear type as well as fish species was developed and incorporated in a GIS of the fishing system and other coastal activities from Ortoire to Guayaguayare.
Participatory GIS is a practice in which local communities share their knowledge and opinions to help generate maps to inform management and decision-making.
Cognitive mapping of fishpot fishing areas showing main fishing area, south east coast, Trinidad
Cognitive mapping by fishers of fishing grounds (by fish species), south east coast, Trinidad
Aquaculture research at the IMA emphasizes the integration of laboratory and field studies to develop scientifically sound approaches to the management of aquatic organisms, production systems, ecosystems and aqua-businesses. The approach is to conduct research in aquaculture with the aim of satisfying the growing requirements of a needed industry which can assist in national food security, food production and the generation of sustainable aquaculture and related businesses.
Aquaculture research at the IMA started in 1984 with an overall goal of conducting field and laboratory trials and developing strategies for the commercial exploitation of targeted species. The species worked on initially were the apple snail Pomacea urceus, the cascadura Hoplosternum littorale, silver tilapia Oreochromis niloticus, red hybrid tilapia and the giant freshwater prawn Macrobrachium rosenbergii.
Fish Cages in Earthen Grow-out Ponds
Malaysian freshwater prawns Macrobrachium rosenbergii have been used in monoculture and polyculture trials at the IMA since 1985. Research on prawn production from monoculture and polyculture with tilapia and cascadura, using locally produced feeds was conducted, and results including stocking densities, and survival and production rates, have been published in reports which are available at the IMA’s library. The prawn is an excellent prospect for polyculture and can be effectively used in polyculture systems with tilapia and cascadura.
Freshwater prawns Macrobrachium rosenbergii at different growth stages.
The IMA initially imported silver Oreochromis niloticus and red hybrid tilapia from Jamaica in 1985 and has further developed good brood stocks. These have been donated to the Sugarcane Feeds Centre, Longdenville; the Bamboo Grove Fish Farm (Ministry of Food Production, Land and Marine Affairs); Orange Grove Fish Farm; the then Caroni (1975) Ltd. and also sold to private farmers.
A market survey conducted by the IMA showed that the red hybrid tilapia was a very popular fish with local consumers and compared very favourably with marine species in terms of colour, taste, texture, and price.
Both laboratory work and field studies are combined to give advisory services to the public, provide training, and produce seed stock for aquaculture development in Trinidad and Tobago.
Silver tilapia and red tilapia hybrid in dipnet at IMA Aquaculture facility
Aquaculture staff sampling fish in Tilapia Recirculating Aquaculture System (RAS)
Early aquaculture research at the IMA with the armoured catfish Hoplosternum littorale was geared towards food fish production systems, fry and fingerling production systems and larval rearing. Work was completed in hatchery methodologies, production systems and marketing of aquaculture products for locally available species. Researchers at the IMA have pioneered and developed methodologies for the commercial production of cascadura. Investigations on the spawning and hatching of this species were conducted in an effort to improve nursery practices and to determine optimal stocking densities in production ponds. Cascadura can be stocked at relatively high densities and is suitable for polyculture with tilapia and freshwater prawns. While natural stocks are being over-fished, there is an increasing demand for cascadura locally and also an export market.
Female and male cascadura in net seine at the IMA
Trade in ornamental fish has been one of the most consistently expanding areas of aquaculture in Trinidad and Tobago. Trinidad was once ranked third (behind Colombia and Brazil) in exports to the US from this region. Not all of Trinidad's exports are from actual local production and there is capturing of wild-caught fish. The practice of catching ornamental fish from our local rivers and streams for export is associated with environmental degradation, habitat loss and reduction in breeding areas. This resource will probably be soon over fished, and farmers are encouraged to be involved in actual breeding and rearing of ornamentals.
Ornamental fish farm in Trinidad
Left: Ornamental fish in tanks at the IMA; Centre: Protozoan parasite Trichodina sp. (x 1,000); Right: Gill of stressed Angelfish Pterophyllum scalare (x 1,000).
The development of this industry will require a well-managed fish health programme. Fish disease outbreaks are often complex, involving both infectious and non-infectious processes. The research conducted by the IMA has enabled its specialists to provide much needed assistance to ornamental fish breeders as they seek to manage their businesses with greater efficiency in ways that do not damage the wider environment.
IMA Technician performing necroscopy on ornamental fish
Technical advice to the public on all aspects of the fish production process and project cycle - from site evaluation, site selection, system design, species selection, pond construction, stocking, rearing, harvesting and marketing of aquaculture products is available through the Technical Advisory Services of the IMA.
Intensive Re-circulating Aquaculture Systems
Trinidad and Tobago is predominantly an oil-based economy with natural gas and petrochemical industries providing the bulk of Gross National Product (GNP). Aquaculture has not been significantly supported or funded as an emerging industry, although there have been some successes in small-scaled fish farms and in ornamental fish breeding, farming and exports. Traditional aquaculture systems which require available land, water and appropriate soil and topography have not stirred the imaginations of potential farmers and entrepreneurs or the local funding institutions for investment capital. The cost of agricultural land is relatively high and successful enterprises are limited. However, increased demand for fish and fish products, coupled with declining stocks as well as the need for diversification in the local economy has seen a renewed interest in aquaculture as a source for fish and as a potential business.
Tank-based Tilapia Production System
The Institute of Marine Affairs (IMA) Fisheries and Aquaculture Research Programme (F&ARP) has introduced re-circulating aquaculture systems (RAS) to improve the efficiency and sustainability of aquaculture production systems. One project based on this system is a collaborative effort with the Seafood Industry Development Company (SIDC) for the development of an intensive production system for growing hybrid red tilapias. There is no successful commercial aquaculture project for food fish in Trinidad and Tobago. This project would serve to demonstrate the possibilities for successful commercial aquaculture and initiate further developments in commercial aquaculture.
Researchers wanted a flexible facility to raise tilapias from the fingerling to adult stage that met strict bio-security standards and which might also be used for other species. Production modelling and bio-programming for the project and final design and layout were prepared by staff of the F&ARP of the IMA. Facility construction began in early 2009 and was completed in September 2009. The facility is being run by IMA staff.
A covered shade-house of approximately 740 square metres and housing two separate production units comprising of six 30,000 litres tanks in each system, two 15 square-metre rooms – one for feed storage and the other a control room securing pumps, blowers, monitoring and alarm equipment - and a shared covered area of 22 square metres between them was constructed. Water is supplied by a 5 cm diameter PVC line from a well with capacity of 450 litres per minute use for supply and makeup water to all systems to satisfy bioplan requirements. Recirculating systems include mechanical and biological filtration, aeration and on-demand drainage lines. The wastewater treatment system designed for the facility includes solids filtration, water storage, fish and egg escapement prevention and management. The system is equipped with water quality sensors, data-logging and alarm systems for effective management. Culture systems are stocked with red hybrid genetically male tilapias (GMT) tilapias and silver GMT tilapia Oreochromis niloticus that were bred and raised in IMA hatchery systems. Preliminary trials are ongoing with data collection on water quality, feeding, growth rates, fish health management, biofiltration, water budgeting and economics. Initial results are encouraging. Since May 2010, fish are being harvested on a weekly basis from the facility and are marketed by the SIDC.
Marine Re-Circulating Production System
Global marine fisheries have exhibited continuous declines in recent years and the Food and Agricultural Organization (FAO) has stated that 74% of the world's commercially fished species are depleted, over-fished or fully fished. At the same time, due to the health benefits associated with a seafood-based diet, consumer demand for seafood has steadily increased. It is very clear that in order to ease pressures on wild fisheries stocks and to satisfy the growing global consumption of seafood, marine species must be produced through aquaculture. One such option is the use of mariculture for environmentally sustainable and economically feasible production systems.
Snappers and groupers are commercially viable fish species. Snappers and groupers belonging to the family Lutjanidae and Serranidae respectively have been cultured in marine cages, fibre glass tanks, and concrete tanks (indoors) or in ponds (outside) in the United States and Asia. Locally, there has been little or no research on the potential of snappers and groupers as culture species.
The snapper species of importance are the southern red snapper Lutjanus purpureus, lane snapper L. synagris and the vermilion snapper Rhomboplites aurorubens while the grouper species most commonly targeted are the yellowmouth (Epinephelus flavolimbatus), and yellowedge grouper Mycteroperca interstitialis. However, there are numerous species that may be cultured in Trinidad and Tobago which include: Lutjanus analis(mutton snapper), L. griseus (gray snapper), L. jocu (dog snapper), L. mahogani (mahogany snapper), L. synagris (lane snapper), L. purpureus (southern red snapper), Epinephelus adscensionis (rock hind), E. guttatus (red hind), E. fluvus (coney), E. itajara (jewfish), E. cruentatus (graysby), Mycteroperca venenosa (yellowfin grouper) and M. tigris (tiger grouper). Long-term and short-term trends in biomass for most of these stocks are unknown and there is no management plan for the fishing of grouper stocks in Trinidad and Tobago. Anecdotal information suggests that stocks have declined and there is urgent need to put management measures in place.
Control Room for Marine Re-circulating System
The Marine Re-circulating Production System is part of the development of models for intensive, re-circulating aquaculture systems at the IMA using several species This project seeks to provide information on the survival and growth of several local snapper and grouper species in a marine re-circulating system as well as investigate the culture potential of other species. It will also seek to promote intensive marine recirculating systems for the production of food fish and marine ornamentals as well as provide facilities for research in other marine organisms such as corals and sponges.
Activities will include collection of fish; acclimatization of fish into a marine re-circulating system; detection and management of pathogenic organisms by pre-examination of fish using histopathological methods; introduction of fish to commercially formulated feed and/or prepared rations; and determination of the feasibility as culture species in a marine re-circulating system. Preliminary trials have already been done and the Marine RAS is being scaled up for new trials beginning late, 2010. Outputs expected are:
- IMA technical reports, short briefs and fact sheets to be published in the reference journal.
- A handbook on activities for extension work to aspiring marine aqua-culturists.
- Use of the in-lab model as a stepping stone for larger commercial tank grow-out and marine cages.