The Effect of ENSO (El Nino Southern Oscillation) phenomenon on Fishing Season of Small Pelagic Fishes in Indonesia Waters

The El Nino Southern Oscillation (ENSO) phenomenon causes changes in environmental conditions such as water temperature, salinity, and rainfall. In fisheries sector, the changing environment has affected the fishing seasons and Catch per Unit Effort (CPUE) of some pelagic species. This research was conducted by calculating CPUE and fishing season index for several small pelagic fishes in Makassar Strait, Bali Strait, and Aceh waters, then comparing the index value with the fishing season pattern in two extreme periods that are 2010-2011 and 2016 - 2017. An ANOVA test was conducted to assess the significant difference between normal and extreme conditions. The results of the analysis showed that there was a significant different in CPUE between average normal condition and ENSO period. Every single species showed different response to ENSO event, mostly decreased in CPUE relate to El Nino event, except for sardine in Bali and Makassar Strait and scad in Makassar Strait. ENSO affects shift in the fishing season of big-eye scad, scad, sardine, and neritic tuna in Makassar Strait, Bali Strait, and around Aceh waters. Indian mackerel in Makassar Strait showed no change in fishing season but the CPUE showed lower than normal condition. This study shows that ENSO was significantly affected fisheries in Indonesia waters.

Sea Surface Temperatures Drive Historical Demography of Deep-Sea Fishes

Demographic histories are largely understood to be a product of their environment, as populations expand or contract in response to major environmental changes. Deep-pelagic fishes inhabit one of the most temporally and spatially stable habitats on the planet, so they may be resistant to the demographic instability commonly reported in other marine habitats, but their demographic histories are poorly understood. We reconstructed the demographic histories of thirteen species of deep-pelagic fishes using mitochondrial and nuclear DNA sequence data. We uncovered widespread evidence of demographic expansion in our study species, a counterintuitive result bases on the nature of the deep-pelagic. The frequency-based methods detected potential demographic changes in eleven species, while the Extended Bayesian Skyline Plots were more conservative and identified population expansion in five species. The dates of expansion largely coincide with periods of warm sea-surface temperature at the northern and southern boundaries for the ranges these species inhabit. We suggest that this is the result of the pelagic larval phase shared by most deep-pelagic fishes, where the larvae inhabit the upper 200 meters. Changes in sea surface conditions likely alter the suitability of the habitat in a given region for the larval phase, affecting the species range and in turn population size. These results are critical to our understanding of how the deep-pelagic fish community will respond to future climatic changes.