Connecting fish, rivers and people: SAIAB celebrates World Fish Migration Day

	World Fish Migration Day, on May 24th, is aimed at increasing worldwide awareness of the importance of freshwater migratory fish, and rivers that flow freely to oceans, as well as the people that depend on them.
	Principal Aquatic Biologist Dr Paul Cowley shared his research on fish movement behaviour at a World Fish Migration Day presentation hosted by SAIAB (Picture: Mitzi du Plessis)
	Juvenile leervis are tagged for monitoring (Picture: SAIAB)
	A fishway tour in the Kruger National Park formed part of South Africa's celebrations of World Fish Migration Day 2014 (Picture: Mitzi du Plessis)
	To mark this global event, the Arase Dam in Japan was removed to restore the original river environment (Picture: Panoramio)

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) to mark this global event.

The presentation, 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.

Fish movement behaviour

Principal Aquatic Biologist at SAIAB, Dr Paul Cowley, shared his research on fish movement behaviour, in particular of important fishery species such as the spotted grunter, dusky kob, white steenbras and leervis, which all use estuaries as nursery areas. 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.

Dr Cowley demonstrated, by means of graphs and pictures, how fish stocks are dwindling due to over-exploitation in South African rivers and estuaries. 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 times 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 (for example, the South African Sustainable Seafood Initiative).

Other events on the day ranged from a fishway tour in the Kruger National Park to the removal of the Arase Dam in Japan to restore the original river environment. The theme running through all these events was "Connecting fish, rivers and people".

A crucial link in the food chain

Migratory fish species support food supply and livelihoods for millions of people, but are now more than ever under great threat. The main causes of this are man-made obstacles. Dams, weirs and sluices built for water management, hydropower, irrigation and land drainage disrupt the natural flow of rivers and can prevent fish migration.

Many fish need to migrate to reproduce, feed and complete their life cycles. Migratory species make up a crucial link in the food chain and play an important ecological role in productive river systems. Giant catfish, sturgeon, eel and salmon are just some of the well-known migratory species under human pressure.

For more information about fish migration, contact saiab@saiab.ac.za.

By Nangamso Myoli, SAIAB