Dinâmica da frota artesanal e reprodução de duas espécies alvo capturadas na reserva extrativista marinha Prainha do Canto Verde, Ceará

Abstract

The Prainha do Canto Verde Marine Extractive Reserve (MER) located in the municipality of Beberibe/CE has a community made up of artisanal fishermen. The objective of this thesis was to characterize the dynamics of the artisanal fleet and the reproductive biology of the main target species: Spanish mackerel (Scomberomorus brasiliensis) and Blue runner (Caranx crysos). During landings, sampled from May 2016 to April 2018, a survey was applied to record information on fishing activity. For the study of reproductive biology, in each landing, the specimens were identified, photographed, weighed (kg), and the morphometric measurements were recorded. Still in the field the gonads of each specimen were removed and the sex was identified based on its shape and color. They were also weighed (g) and had fragments removed for later histological analysis and confirmation of the stage of sexual maturation. A total of 382 landings at two landing points were monitored. Only non-motorized boats are allowed in the Reserve, approximately 77% of the vessels were row-boats and the other 23% were small sailing rafts. Most fisheries are of the “one day trip” type representing ~77% of the trips. The number of fishermen per boat varied from one to four, most often two fishermen per boat (~47%), followed by three fishermen (~32%). In total, 31 fishing sites (fishing grounds) were used, where artificial reefs presented a higher frequency of occurrence, followed by the shipwrecked sailboat, which works as an artificial reef for collective use. Five fishing gears are used, with emphasis on the use of the handline, with ~62%, followed by the gillnet (~30%). The monthly cost of fishing activity varied according to the modality, where the median was R$ 10,00. A higher catch per unit of effort was recorded for the handline gear with a median of 0.42 (kg/fisher*hours). In the gillnet fishery, the median was 0.08 (kg/m2*hours). The largest productions were reported for Spanish mackerel and blue runner. For a total of 360 Spanish mackerel sampled, the sex ratio was 1M: 2.42F. The maximum GSI occurred between June and August/17. The length at first maturity (L50) recorded for both sexes was 46.8 cm in total length, but when separated it was 44.7 cm for females and 47.5 cm for males. The individuals captured by handline had a median of 83 cm total length and 50 cm gillnet. For the blue runner 375 specimens were analyzed, the sex ratio was 1M: 2.86F. The maximum GSI occurred between May and June/17. The L50 recorded for both sexes was 28.8 cm in total length, when separated it was 28.71 cm for females and 30.7 cm for males. The specimens captured per handline had a median of 47 cm total length and 35.5 cm for gillnet. The most intense spawning season was from May to August, when GSI reached its maximum values and the highest frequency of mature individuals. Management measures are needed for the Spanish mackerel fishery as the average catch size is very close to L50 and may compromise the resource in the future due to growth overfishing. In the blue runner fishery, it was observed that the capture by gillnets retains smaller specimens, however, the class with the largest number of individuals was close to L50. This information is important for the development of fisheries management strategies that guarantee the sustainable exploitation of fisheries resources.