The effects
of over-fishing was the topic of discussion at a World Fish Migration Day
presentation hosted by the South African Institute for Aquatic Biodiversity
(SAIAB). The presentation to mark this global event which took place at the
Port Alfred River and Skiboat Club on 23 May 2014, aimed to highlight the
ecological and social importance of migratory marine fish species and how they
are threatened by human activities. Similar celebrations took place at over 270
sites around the world.
Principal
Aquatic Biologist at SAIAB, Dr Paul Cowley shared his research on fish movement
behaviour, in particular important fishery species such as the spotted grunter,
dusky kob, white steenbras and leervis which all use estuaries as nursery
areas. He also demonstrated through graphs and pictures how due to
over-exploitation of fish in rivers and estuaries around South Africa, fish
stocks are dwindling. Many species of fish migrate between the sea, estuaries
and rivers to complete their life cycles. Fish tend to move into the shallower,
less saline water of the estuary to spawn.
The
presentation was based on data collected from tagging studies and acoustic
tracking research undertaken in several estuaries in the Eastern Cape including
the Kowie River. According to the Daily
Dispatch (27 May 2014, p.5), surveys in popular areas have revealed fishing
activity was on average five time higher in the estuary than on the coastline
and ten times higher during the holiday season.
Dr Cowley
said the way to prevent species from being fished out was to practise tag and
release protocols and for consumers to buy only fish identified as sustainable
by experts. Other events on the day ranged from a fishway tour in the Kruger
National Park to the removal of the Arase Dam in Japan. The running theme
throughout all these events was connecting fish, rivers and people.
