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Research Voyages

Voyage to the Gulf of Carpentaria

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THE VOYAGERS

Putting in the sleds and nets

Ted Wassenberg will be sampling familiar waters on the Southern Surveyor voyage, and looks forward to finding his favourite creatures in the sediments.

Clorid wassenbergi, the mantis shrimp that bears Ted Wassenberg’s name.

John Salini forsees a busy voyage ahead, without the usual number of hands assigned to sampling fish.

John Salini and Ted Wassenberg make way for ecosystem-based sampling

In their 60-plus years with CSIRO, John Salini and Ted Wassenberg have seen a mountain of prawns landed on the deck of the Southern Surveyor. On this voyage, their twentieth between them, they'll take turns to coordinate the sampling procedures for fish, prawns and other benthic (bottom dwelling) invertebrates. They're a little apprehensive, however, because they've never had to share the deck with such a broad array of sampling activities.

"In past voyages we've focussed on net sampling, so we've have four or five people available to sort the catch," Mr Salini says. "But this time we'll be sharing the deck with geologists, ecologists and oceanographers, so we'll learn quickly the etiquette of multi-tasking."

The first operation at each sampling station, (while the ship is stationary), is to sample the water and measure its temperature and salinity. Secondly, the box corer will be lowered three times to grab three perfect cubes of sediment for various forms of interrogation. Then the biologists will have their turn.

Sampling experience

The benthic sled will be towed for three minutes along a 200-metre stretch of seabed, to gather a representative sample of animals such as sponges, gorgonians, bryozoans, crustaceans and other invertebrates.

These creatures are a special area of interest for Ted Wassenberg who has a quiet yearning to author a pictorial guidebook to crustaceans. His particular favourites are the stomatopods or mantis shrimps, so-named because they have a similar armature to the land-based preying mantis. He has found lots of stomatopods through the middle and northern gulf, and has one named after him, Clorida wassenbergi.

Mr Wassenberg expects to see differences in the abundance of fixed invertebrates such as sponges and gorgonians in areas of different trawling intensity. "In heavily trawled, soft-bottomed areas we may see more hard urchins, and some changes in fish composition, such as increased levels of grinners," he says.

Fish and prawns will be sampled with a benthic net in a 10-minute operation that sweeps a one kilometre stretch of seabed. Catches from both sled and net will be sorted, identified, measured, counted and weighed. Although they don't expect too many surprises, any particularly interesting or unusual specimens will be preserved for later study.

The water, sediment and biological sampling operations will be repeated at more than 100 sampling stations during the 27-day voyage. "We expect to have to get through all the sampling activities seven or eight times on many of our 12-hour shifts," Mr Wassenberg says.

Before facing the challenge, however, the biologists have an important matter to sort out: who gets the dreaded midnight to midday shift. They say they always toss a coin for it, but probably won't get around to it until they're aboard the ship. "Heads for one shift, tails for the other."

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Updated: 29/03/07