Biological and technical interactions of the major gears in the
demersal fishery in the Gulf of Nicoya and the importance of the mangrove forest for the
sustainability of the fishery
Mauricio Vargas
Biological and technical interactions
Biological interaction is caused by competition for the same food resources and
through predator-prey relationships. In the Gulf of Nicoya,
technical interaction may for example exist between the longline and the trawl fishery. As
young shrimp are an important food item for large sciaenids and snappers, an increased
effort in the trawl fishery may affect the food resources of these fish and affect the
fishery.
Technical interactions exist because gears primarily directed at one species also
catch other species, or certain life stages of one species are caught in different gears.
In the Gulf of Nicoya this happens for example in the gillnet fishery where large
sciaenids are caught in the 3.5 inch nets that are primarily directed at large shrimp.
Another example is the bycatch of the shrimp trawls, where many juveniles of commercially
important finfish are caught as bycatch (See trophic relationships
in the Gulf).
Research activities
Available fishery statistics are being analyzed to create a general picture of the
fisheries in the Gulf. By analyzing the INCOPESCA (Costarican Fisheries Institute)
database, strata (time, location, gears) in the fishery will be identified and
recommendations for a catch and effort sampling design will be made (See fish landings in Costa Rica).
Technical and biological interactions will be identified by sampling the bycatch in the
gillnet and trawl fisheries and by analyzing stomach contents.
The stock dynamics of the major commericial (mainly Sciaenidae and Lutjanidae)
species will be analyzed using both length-based methods and hard body structures.
The role of the mangroves in the recruitment of these species will be assessed by looking
at the distribution in time and space of their juvenile stages in the mangroves.
Finally, recommendations to reduce possible interactions and optimize fisheries management
will be done.