Early increases in artisanal shore-based fisheries in a Nature-based Solutions mangrove rehabilitation project on the north coast of Java

Abstract

We studied nearshore diurnal fish catches and fisheries development in the early stages of mangrove rehabilitation around the village of Timbulsloko on the central north coast of Java, Indonesia. Mangrove rehabilitation was part of a Nature-based Solutions project to re-establish ecological and economic resilience by combining coastal engineering measures with ecological recovery in conjunction with sustainable land and resource use. Creel surveys were conducted during the onset of the monsoon season October–December 2017 to document yields of the three main fishing gears targeting mangrove finfish in a 419 ha mangrove backwater basin. These were accompanied by structured interviews to obtain fisher views on developments in these fisheries. Analysis of satellite images and GIS-mapping were used to follow developments in mangrove coverage and effort in the estuarine lift-net fishery. Mangrove recovery between 2005 and 2018 achieved 8.5% of its maximum possible (historic) cover potential in the basin and followed an exponential growth curve. The increase in lift-net installations targeting finfish lagged in comparison to mangrove increase, remaining virtually zero till 2014, after which it rapidly increased. A baseline study in 2015 found no mangrove-associated finfish fisheries occurring in our study area. The 51 fishers surveyed in 2017, indicated that fishing activity in the area had strongly increased since 2015, with 45% of fishers stating to having started fishing this area a year earlier or even more recently. A significant majority of 87% of respondents with more than one year of experience at this location, stated that their catches had changed in terms of either fish size, quantity or composition since they started fishing, while 86% indicated improvement in terms of either size or quantity. Fishing generated about 1.05 ± 1.11 (SD) USD/hr worth of catch to professional fishers using either of the two net-types studied. As per 2017, fishing had become profitable in our study area, whereas this kind of fishery practically did not exist prior to 2014. We suggest that higher profitability may partially explain the rapid growth seen in fishing activity in the mangrove rehabilitation area. However, for 12 of the 18 larger species caught, the mean size in the catch was lower than mean size of maturation, indicating that these fisheries were principally targeted towards immature nursery fish. The results highlight the need to manage this currently developing fishery, otherwise any benefits to the local community might be nullified by overfishing.