Coastal communities in the district are on a high following a jump in tuna catch by fishers. Catch rates this season have been exceptional, harking back to the pre-1980s, say fishermen.
Traditional fisherfolk operating in near-shore waters have reported good catch of the bullet tuna ( Auxis rochei rochei ), black skipjack tuna ( Euthunnus lineatus ), mackerel tuna ( Euthunus affinis ), and striped bonito ( Sarda orientalis ), both by line and net.
However, the euphoria over surge in tuna landings has been dampened to some extent by the sharp drop in price.
“We have seen prices plunging to 20 per fish, a fifth of what it used to be before the bonanza,” says Robert Panipilla, coordinator for Friends of Marine Life, a local NGO, highlighting the failure of marketing management in the sector.
Other fishes too
Apart from tuna, fishers have also received good catch of sardine, mackerel, ribbon fish, scad and anchovy during the season. While a section of fishermen attribute the increased presence of tuna in the near-shore areas to a recent algal bloom, scientists feel that there are other reasons for the seasonal surge.
“The species composition has been changing over the years, probably because of variations in the marine food web structure. While sardine and mackerel were the dominant species for the past 20 years, they were joined by the scad and finned bulleye last year,” says A. Biju Kumar, Head, Department of Fisheries and Aquatic Biology, University of Kerala.
Scientists feel that the abundance of tuna in local waters may be only a temporary phenomenon.
“As a predatory species which feeds on other fishes, the tuna cannot be directly linked to the algal bloom. However, there is a possibility that it was attracted by the presence of smaller fishes which thrive in the phytoplankton-enriched waters,” Mr. Kumar says.
Nutrient run off
The enhanced nutrient run off during the monsoon is believed to be a major factor triggering algal blooms.
Scientists and fishermen are unanimous in their demand for detailed investigations into the changing composition of marine species and the influence of climate change on migration of fish.
“Old timers believe that any change in the dominating species could signal long-term changes in the marine environment,” says Mr. Robert.
