Bird studies reveal ocean's health
In the Abrolhos: feeding, breeding and the fishing industry
His work is a vital key to whether the area
can sustain parts of the local fishing industry and can accommodate tourism.
He has been investigating the link between the seasonal water currents, the availability of fish (the birds' food supply) and the breeding rates of the marine birds.
Dr Surman has expanded his research following a study that is part of a three-year collaboration between Fisheries WA and Murdoch University, which has been funded by Fisheries WA and the National Heritage Trust.
Since 1990, when he did his honours research, Dr Surman has been building up a picture of the feeding and breeding habits of a range of terns and shearwaters on the Abrolhos. He has spent some months of every summer living under an old guano-boat jetty on Fin Island in order to do his research.
The genesis of his current study came a few years ago when he noticed the breeding season of terns starting later.
"I was scratching my head wondering why. I started to look at the relationship between the current and the breeding success of birds."
Since then he has monitored the current using data from the National Tidal Facility at Flinders University.
"The Leeuwin Current does seem to affect some bird species, especially the starting time of their breeding season," said Dr Surman. "Breeding is delayed when there is a strong current."
He said the adult birds needed to be in good physical condition before they could lay the eggs and successfully rear their young.
That depended on the availability of the fish and crustaceans that the birds eat.
Here's where the second part of Dr Surman's study comes in -- the impact of local fishing on the birds' food supply. Although the main fishery of the region is crayfishing, two other types are of particular interest to Dr Surman and the local fishing industry -- netting scaly mackerel (a sardine-sized fish that the birds eat, too) and long-line tuna fishing.
Netting could cause a real problem if it were overdone, said Dr Surman. He cited the case of over-fishing of anchovies along the South American coast which has caused a reduction in seabird populations from millions to tens of thousands. Dramatic losses have occurred in Europe, too, as a result of netting small fish for cat food and fishmeal.
Obviously net fishing is in direct competition with the birds for the same food. In the case of tuna, the effect is indirect. The birds don't eat tuna, but they need tuna to prepare a meal for them. The surface-feeding birds, like terns, wait for big fish, like tuna and spanish mackerel, to "school-up" the small fish towards the surface where the trapped school becomes prey to the big fish from below and the birds from above.
Dr Surman will monitor the diet and breeding patterns of the birds to assess the role that fishing plays.
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| Brown Noddies | Roseate Terns | Lesser Noddies |
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