Search Results

Oct

26

2007
 
 

Fishing for information



When scientists’ knowledge runs thin, turn to the experts to understand tuna a fisherman's taleFind a drifting log floating around the western Indian Ocean, attach GPS, sonar, echosounding and bird-detecting radar devices, slap on a radio transmitter and voila! The best way to catch tuna. The pelagic predators are attracted to floating objects, knowledge that master fishers have used to locate their quarry: at least 2100 so-called drifting fish aggregating devices (DFADs) are currently bleeping away in the area. However, little is known about how DFADs are “colonized”, the diversity of species present, or the factors that influence fine-scale tuna behaviors around them. These questions are hard and expensive to tackle experimentally, so Gala Moreno, a marine biologist at the AZTI Tecnalia, Spain, and colleagues took a different approach to the problem: they asked the experts what they knew. A series of interviews with members of the devastatingly effective European purse-seine tuna-fishing fleet uncovered much-needed information about how DFADs attract marine species. Reporting their findings in the Canadian Journal of Fisheries and Aquatic Sciences, the master fishers’ hard-won knowledge has obvious value in future management planning. Bringing researchers and fishers closer together could also ease past conflicts and misunderstandings. It could even ultimately benefit tuna, though the individual fish in your sandwich might disagree. Source: Moreno G, Dagorn L, Sancho G & Itano D (2007) Fish behaviour from fishers’ knowledge: the case study of tropical tuna around drifting fish aggregating devices (DFADs). Canadian Journal of Fisheries and Aquatic Sciences DOI: 10.1139/F07-113 Related story in Conservation magazine: 10 Solutions to Save the Ocean Image © gprentice

Filed Under Community-based conservation, Economics and conservation, Endangered species, Marine, Monitoring, Socio-political issues, Tools and technology | Leave a Comment

Email This Post Email This Post

Jun

12

2007
 
 

Six degrees of separation



Anchovy and sardine populations take turns to collapse: it’s a temperature thing where's the fish?Anchovy and sardine fisheries are famous for their dramatic collapses, but a new study suggests the cause isn’t overexploitation. Writing in the Canadian Journal of Fisheries and Aquatic Sciences, three Japanese biologists led by Akinori Takasuka at the National Research Institute of Fisheries Science, Yokohama, show that the optimal temperatures for anchovy Engraulis japonicus and sardine Sardinops melanostictus larvae differ by around six degrees centigrade. When climate-induced oceanic regime shifts warm the seas, anchovies do well but sardines collapse. At a distinctly chillier 16.2 degrees, the boot is on the other foot, giving sardines the edge. However, the fish harvest is important in allowing stocks to recover as part of their natural 50-year basin-wide ups and downs. Source: Takasuka A, Oozeki Y & Aoki I (2007) Optimal growth temperature hypothesis: why do anchovy flourish and sardine collapse or vice versa under the same ocean regime? Canadian Journal of Fisheries and Aquatic Sciences DOI: 10.1139/F07-052 Related story in Conservation magazine: Point of No Return Image © Robert Kyllo

Filed Under Climate change, Economics and conservation, Marine, Monitoring, Restoration, Socio-political issues | Leave a Comment

Email This Post Email This Post

Apr

14

2007
 
 

Flushed with success



invasive species depth guideGreat Lakes ecosystems vulnerable to non-native species carried in ships’ ballast tanks Life for many invasive aquatic organisms doesn’t get much better than stowing away in a ship’s ballast water, hitching a free ride from one side of the globe to the other. The scale of the problem is highlighted in a paper published recently in the Canadian Journal of Fisheries and Aquatic Sciences. John Drake and University of Notre Dame colleague David Lodge took water and sediment samples from the ballast tanks of ships entering the North American Great Lakes. By laboriously examining the tiny creatures by microscope, they were able to identify at least 93 species, many of which were non-native. Their results suggest that during the three-year collecting period alone at least 17 potentially invasive species were introduced to the Great Lakes, likely a huge underestimate given that they didn’t include microorganisms or plant seeds in the analysis. Unlike the tanks themselves, the need for tighter regulation in when and where they are emptied is pretty clear. Source: Drake JM & Lodge DM (2007) Rate of species introductions in the Great Lakes via ships’ ballast water and sediments. Canadian Journal of Fisheries and Aquatic Sciences DOI: 10.1139/F07-029 Image © Tarek El Sombati Related stories in Conservation magazine: Empty tanks

Filed Under Fresh water, Invasive species, Marine, Restoration | Leave a Comment

Email This Post Email This Post