Thursday, May 30, 2013

Arapaima: One of the largest freshwater fish in the world

Lurking in the lakes and rivers of the Amazon basin are some of the most unusual fish you are likely hear about. Arapaima have been recorded up to 3 meters in length and over 200 kg. This fish has been featured on River Monsters and its history is deeply rooted in local tribal traditions. In addition, its biology could be considered unusual.
Due to the long history of being an important indigenous food source, arapaima are one of the few fish which are threatened in their home range while simultaneously being of management concern outside of its native region. Bolivia and Peru both show some evidence that this non-native piscivore can deplete populations of native game fish. This polarity of concern makes policy and management, especially outside the Amazon basin, a difficult task. While much is known about arapaima biology, population estimates can be tricky due to its widespread nature. It is known however, that near large human developments, this fish is functionally extinct. Restrictions on size and season are in place, but poorly enforced.

Arapaima reproduce according to the flood pulses of the mighty Amazon basin, migrating laterally along tributaries into numerous surrounding lakes. In February through April, when water levels are their lowest, these fish spawn in floodplain lakes. Parental care is a large component of arapaima biology and the young are often seen clustered around the father’s head. Rearing of young is timed just before the rainy season comes. Males will guard the nest and the young, and even help the offspring complete their first migration into the tributaries as water levels rise. There is even some observational evidence that arapaima “learn” to feed from watching their father as they travel out of the lakes and into the rivers.

The greatest concern for the future of this fish in its native range is due to its vulnerability to detection while guarding nests. Arapaima, which is in the bony tongue order, is an obligate air breather, and must surface every 10-15 minutes to breathe. The signature sucking sound is like a dinner bell to harpooners, who have honed their skills to hunting this fish. Historically, the best time to hunt was during the dry season when arapaima are cut off in floodplain lakes. This is also their spawning season. Without care, the eggs and young arapaima cannot survive, and this is the major cause of population decline. While regulations seek to restrict hunting arapaima during this time, there is little enforcement. When coupled with a lack of population estimates, it is exceedingly difficult to know the current status of this fish in its native range. It is clear however, more study is needed to determine how threatened this species is and what level of protection is required.

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  1. Very cool! I find it interesting that they are trying to conserve them in the native range and manage them as non-natives elsewhere. A unique management predicament!

  2. If only zebra muscles could be "creatively managed" as well...