Divergence in buoyancy of the ecologically similar nototheniid fish Notothenia coriiceps and N. rossii

BARRERA ORO, E. R.; EASTMAN, J. T.; MOREIRA, E.

Capital Federal.

Conferencia; SCAR XXXI & OPEN SCIENCE CONFERENCE.; 2010

SCAR e Instituto Antártico Argentino

Although lacking a swim bladder, notothenioids inhabit pelagic and benthic habitats and diversification in buoyancy is the ecological hallmark of their radiation. We studied the buoyancy of sister species Notothenia coriiceps (NOC) and N. rossii (NOR) captured at King George/25 de Mayo Island. Measurements of buoyancy are expressed as percentage buoyancy (%B = weight in water/weight in air x 100), with smaller numbers reflecting more buoyant (i.e., less dense) species. Our samples encompassed a large number of individuals of wide size/age ranges: 95 NOC of 64?475 mm TL and 1?13 years; 99 NOR of 78?436 mm TL and 1?7 years. Both species are benthic as adults and have complex life cycles involving pelagic stages and migrations. Mean %B of NOC (4.34%) was significantly greater (t = 11.256, P