Infra-red video of fish on Hatton Bank
August 31st, 2008 | Published in General ecology, Marine ecology
During June/July 2008, I was once again privilaged to join my Dutch colleagues on the RV Pelagia, a magnificent research ship from the Royal Netherlands Institute for Sea Research. The cruise yielded a huge area of multibeam bathymetry, physical oceanography and insights into the biodiversity of the area.
One particularly notable attempt was to quantify and identify the fish community in the area, the water depth is nearly 1000 m. We used a timed bait release system mounted on the ALBEX lander and attached a new SAMS infra-red camera.
The results were pretty good. You can see a sneak preview below:
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Limpets, predominantly Patella vulgata, have been associated with damaged or receding canopies of Ascophyllum nodosum. Although the damage results from limpet grazing, the benefits that limpets gain from this behaviour are unclear as A. nodosum is thought to be well defended from grazers by anti-herbivore compounds. In this study, P. vulgata individuals were enclosed at densities between 80 and 320 m-2 at two sites within Strangford Lough. Limpet growth and limpet survival were compared between unsubsidised controls and treatments in which limpet diets were subsidised by fronds of A. nodosum. When subsidised, limpet residual growth rates were significantly higher and mortality was lower than in unsubsidised control treatments. Individual limpets consumed a similar amount of A. nodosum regardless of limpet density. Higher densities of limpets therefore consumed more A. nodosum per replicate. The effects of A. nodosum in maintaining limpet densities could resonate through sheltered rocky communities. The importance of a macroalgal subsidy in supporting limpet populations may have been underestimated or overlooked in earlier studies. Therefore, the extensive and productive macroalgal canopies that characterise many sheltered temperate rocky shores could be more sensitive to increased limpet abundances than previously thought.