Abstract

Shrimp trawling is the main deepwater fishery in Costa Rica, where Solenocera agassizii Faxon, 1893 has represented up to 30 % of total shrimp landings for the Pacific coast. Despite the species’ economic importance, knowledge about its biology is limited, hindering the development of an appropriate management plan for a sustainable extraction of this resource. The goals of this study were to estimate the size at onset of maturity (SOM) and to describe the reproductive dynamics of S. agassizii in order to provide information that will help to establish a minimum legal landing size and a possible fishing closure during its reproductive period. A total of 4 273 specimens (2 175 females: 2 098 males) were analyzed between January 2007 and January 2008. The overall average size was 30.8 mm CL (carapace length), with females larger (32.4 ± 5.7 mm CL) than males (29.1 ± 4.0 mm CL). SOM was estimated with a logistic regression for females (SPM: size at physiological maturity) and as the breakpoint in the CL-TL (total length) regression for both sexes (SMM: size at morphological maturity). Males reached the SMM at a larger size (32.4 mm CL) than females (30.3 mm CL), whereas the SPM for females was 37.8 mm CL. The percentages of specimens caught below the estimated SMM were 77.4 % (males) and 52.1 % (females), whereas 79.2 % of the females were below the estimated SPM. Mature females were obtained on a monthly basis, indicating a continuous reproduction of S. agassizii with peaks between July and October. These peaks coincide with months with high precipitation and coastal upwelling. In 2013, Costa Rica prohibited the granting of new commercial shrimp trawl licenses, as well as the renewal of existing licenses. Consequently, unless the sustainability of this fishery is scientifically proven, all existing licenses will expire in 2018. The results of this study indicate that the current fishery of S. agassizii in the Pacific coast of Costa Rica is not sustainable. Hence, the assessment of mesh selectivity for this fishery - to ascertain catches were the average size caught is equal to or greater than the SOM - is urgent, as well as the establishment of a MLS of 112.6 mm TL (37.8 mm CL) and a fishing closure period in June and July. These recommendations aim to protect the spawning population and immature individuals of S. agassizii. Nevertheless, it is recommended to study the viability of employing alternative fishing gears to reduce the percentage of immature individuals captured and to avoid an overexploitation of the resource.