Fish larvae study stirs marine park debate
Marine parks A new study on the dispersal of fish larvae has reignited a debate on the science behind marine parks.
Leis says marine parks can be a source of fish for other protected areas, as well as areas that are currently used by recreational and commercial fishing.
"You can get biodiversity protection plus the bonus of fish babies for the fished areas," says Leis, who is also an honorary research professor at the Institute for Marine and Antarctic Studies at the University of Tasmania.
He says understanding how far fish larvae disperse will help in planning the location of marine parks so they can act as a connected network of breeding populations of fish, and provide maximum benefit to both fisheries and conservation.
To date most research on larvae dispersal has been carried out in tropical areas, says Leis, but there is now increasing interest in marine parks being established in temperate areas.
"The question is do we have to do all this research again in cooler water areas or can we apply what we have learned in the tropical areas to what's going on in temperate zones," says Leis.
In the past the assumption has been there are fundamental differences in larval dispersal between cooler and warmers water.
Leis says this has been one factor slowing down the establishment of marine parks.
"It's very common for people who oppose a marine park in a particular area to say there is no research from the area to show there are any benefits to fisheries," he says.
Now in a study of shore fishes, Leis and colleagues found no "clear evidence" for latitudinal differences in larval dispersal.
Among other things the researchers studied the length of the larval phase, the effect of water temperature, and larval swimming abilities and feeding rate, all of which could impact on their dispersal.
"The bottom line message of this paper is that the presumptions that have been made in the past are not supportable by what we know," he says.
Leis says the findings remove one potential barrier to the creation of marine parks in temperate areas - the need to get local data on larval dispersal.
Fisheries ecologist Professor Colin Buxton of the University of Tasmania describes Leis' research as "very interesting".
"It adds quite significantly to our understanding of how larvae are dispersed in the ocean," says Buxton.
But, he says larval dispersal from marine parks does not necessarily benefit fisheries.
He says there is no data showing there is a shortage of larval fish in the first place in Australia's fished areas, and no evidence showing marine parks give measurable improvement in yield.
"Governments tend to talk about a network of marine parks that will benefit everybody but it's a long bow to draw," says Buxton.
"There is very little science that actually quantifies that is an actual benefit.
"The whole question of whether [marine parks] will benefit fisheries is a highly contestable position and it's a position our governments take based on a very weak scientific argument.
"This paper is probably very valuable for understanding connectivity of marine protected areas from a biodiversity perspective, but less so for the whole argument of whether marine parks are a socially and economically effective fisheries management tool."
Marine ecologist Associate Professor Emma Johnston from the University of New South Wales agrees there is debate over the benefit of marine parks to fisheries.
"There's increasing evidence marine parks are good for fisheries but there are still a lot of knowledge gaps that we need to fill," says Johnston.
"But it's important to remember that most marine parks aren't there specifically to support fisheries."
She says regardless of whether marine parks increase the number of fish in adjacent fished areas, evidence suggests they could still play a key role in sustainable fishing.
"Marine reserves play a potentially important role in allowing a greater genetic diversity of the fish stocks," says Johnston.