Abstract

NEVES DE CARVALHO, André; VAZ, Ana Sofia Lino; SERGIO, Tânia Isabel Boto  and  SANTOS, Paulo José Talhadas dos. Sustainability of bait fishing harvesting in estuarine ecosystems: Case study in the Local Natural Reserve of Douro Estuary, Portugal. RGCI [online]. 2013, vol.13, n.2, pp.157-168. ISSN 1646-8872.

A narrow relationship between marine resources and local populations always existed in fishing communities of coastal areas. In the Portuguese estuaries bait fishing is a common practice in which gatherers collect intertidal species such as seaworms, shrimps, crabs or clams. In recent Local Natural Reserve of Douro Estuary (RNLED) this activity is fairly entrenched due to the proximity of a great fishing zone, the Afurada, and the abundance of recreational fishermen operating in the area. This study aimed to quantify the impact of bait fishing gathering on the ecology of this estuary benthic community, in order to propose management measures for this activity, ensuring its sustainability, and to verify the influence this activity may have on the conservation of intertidal resources in a protected area. Between June 2010 and May 2011 monthly samples were collected in the intertidal zone, in order to quantify the density of populations of Hediste diversicolor and Scrobicularia plana at two locations in the estuary. During the same time period, weekly interviews were performed to bait fishing gatherers operating in RNLED area. In this area of Douro estuary, (239.7ind/m2) was the most abundant species compared to the clam S. plana (0.3ind/m2). In the area of RNLED the species most collected by bait fishing gatherers was the polychaete , and it is estimated that each year 9.9tons are captured, representing an annual mean catch per bait fishing gatherer of 0.3tons. However, the total annual biomass collected was substantially less than the productivity estimated for the entire intertidal area of RNLED (78.7 to 141.3tons). The number of bait fishing gatherers varied between 0 on December 2010 and 12 in July 2010, showing a decrease in activity in the RNLED, especially during the times when surveillance occurs. The area prospected by each gatherer was estimated to be 10m2/day. Considering both tides and all the effort done by an average of 8 men/day, the prospected area was 80m2/day, corresponding to 0.3% of the intertidal area. This effort was mainly concentrated in about 1/3 of the available intertidal area. Results indicated the sustainable management of bait fishing activity in the referred protected area is possible. However, other aspects must be taken into account, such as the possible conflict of this activity with biodiversity conservation in the reserve. Therefore, we suggest some possible solutions for the sustainability of this activity, along with less disturbance to birds that may feed in the reserve, such as: delimitation of a marginal area within the reserve, smaller than the current one, where the collection of organisms is allowed, as well as the oversight and control of licenses and educational procedures. Moreover, these measures would have a positive impact in the integrated management of the reserve, while enabling an activity with positive economic consequences in an underprivileged population. Also, they will contribute to lower the impact of human presence on the avifauna and on the structure of the sediments.

Keywords : Douro Estuary; Protected Area Sustainable; Estuary Management; Hediste diversicolor; Bait Fishing Harvesting.

        · abstract in Portuguese     · text in English     · English ( pdf )