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Bay of Ambaro (Madagascar) - Exploitation

The Bay of Ambaro is mostly known for its shrimp fishery, which simultaneously makes incidental catches of numerous fish species and other megafauna including marine turtles, sharks and rays. The exploitation is sequential, the traditional multi gear segment operating mostly in tidal areas and the industrial fishery using bottom trawls operating at between 5 and 30 m depths. The industrial segment commenced in 1967 after the first stock prospection, and developed progressively. The shrimp catch increased along with fleet development from the beginning of the fishery until mid 1990s, the annual catch fluctuating around 1,300 - 1,600 MT, considered as the maximum sustainable yield, with a peak at 1,740 MT in 2003, then dropped to 540 MT in 2005 and 600 MT in 2007. The situation continued to worsen in 2008, 2009 and 2010. No evidence for a link between declining catch and environmental parameters has been found. However, a significant increase in coastal traditional effort targeting juveniles and sub adults was reported. One of the provisory conclusions drawn is that there has been biological overexploitation of juvenile and subadult stages, impacting on the recruitment in trawl fishing grounds.

Of the 5 species encountered, Fenneropenaeus indicus (H. Milne Edwards, 1837), previously called Penaeus indicus, dominates the shrimp catch; its contribution fluctuates significantly over years (from 94% in 1978 to 30% in 1998, increasing again to reach a sudden peak in 2004, then decreasing back to 50 – 60% from 2005) as well as monthly.

The shrimp fishery discards at sea a great amount of bycatch, the most common species belong to the family of Leiognathidae. 32% of the estimated 1491 MTons of bycatch during the low season of 2005 was discarded. Many management measures have been adopted successively, relating to characteristics of fishing gears, closure season, level of effort, number of vessel operating, use of turtle excluder devices (TED) and bycatch reduction devices (BRD), etc. Currently, industrial fishing companies are voluntarily reducing their fleets and increasing their bycatch landings for profit. A trend to convert trawlers into fish liners is suspected; commercial prospection is underway. The fringing reefs sprinkled over the continental shelf support a traditional handline fishery, targeting about 55 reef fishes in 18 families, the most common ones including Serranidae, Lutjanidae, Caesionidae, Lethrinidae, Haemulidae and Scaridae. No records are available to assess the trends. However, their propensity to schooling makes the stock highly vulnerable, and actually, traditional fishermen operating in the area reported a decrease both in quantity and size of fish caught. Due to intensive shark finning fishing, shark populations appear to be declining, as well as those of commercially important holothurians.