Report 4: More of the same

Steve Nicol, Voyage Leader 

BROKE-West falling off the edge of the known world

BROKE-West falling off the edge of the known world
Photo: Steve Nicol

The survey so far has largely been an oceanographic affair, although there has been considerable activity on the part of those looking at the microscopic elements of the marine ecosystem and at the other end of the food chain, the charismatic megafauna – the birds and whales. Later this week we will begin the north-south transects which is when the more intensive sampling will occur, where we start to deploy the net and really put the echosounders through their paces. The area we have chosen to survey is actually a management area designated by CCAMLR – the Commission for the Conservation of Antarctic Marine Living Resources – the body that manages the fisheries of the Antarctic region. This large area is known as Division 58.4.2 and is bounded on the West by 30°E, on the East by 80°E and to the North by the 62°line of longitude. CCAMLR manages fisheries by setting catch limits in its statistical areas based on estimates of abundance of the target species. For the purposes of our survey we are interested in the abundance of krill which is the subject of the largest fishery in the Antarctic region. There is a standard way to estimate the abundance of krill and this consists of using the echosounders on a number of transects that run perpendicular to the coastline, ground-truthing the results obtained from the sounders with a number of net tows and then using some very fancy statistics to come up with the biomass of krill for the region. Coincidently enough this sort of survey design is also pretty close to that required for a detailed oceanographic survey which explains the rather unholy alliance of oceanographers and ecologists on the voyage. Combining the efforts of the two groups has benefits, other than those derived from extreme social engineering, and these include being able to build a complete picture of the entire ecosystem of the region from the ground up. This will allow us to better understand how it functions and how it might be affected by pressure from increased fishing or as a result of climate change.


Jason listening for whales

Another day at the office - Jason does some filing while listening for whales
Photo: Steve Nicol

But right now we press westwards along the north of the survey area dropping CTDs into the water about twice a day and collecting underway data as we steam between sampling sites. There is obviously a deep yearning amongst the biological contingent to start making a contribution and unconfirmed sightings abound. These include a giant squid attacking the CTD one night (hallucinated by Tim the second mate), surface swarms of krill (thanks Jason, you can go back to bed now) and large numbers of whales which seem to disappear as soon as anyone other than the whale team are on the bridge. Strange things are also showing up on the echosounders and Toby, our acoustician, has his itchy finger hovering over the red button. Pressing this button will initiate a target trawl at which point the entire ship's company drops what it is currently doing, the ship executes a speedy U turn and the net is stealthily manipulated into the object of interest that has been detected on the echosounder – obviously not something done lightly but a procedure that we will be following some 50 times over the course of the next 6 weeks
The little net goes in search of appendicularians

The little net goes in search of appendicularians
Photo: Steve Nicol

We have been regularly deploying a smaller net at the CTD station and the aim of this sampling is to collect apendicularians – small, delicate creatures that are highly abundant, but which are rarely seen because of their fragile nature. But if the animals are fragile then the collecting net proved to be equally so and returned after its first sortie minus its bottom which made its usefulness doubtful to say the least. Luckily our science support officers Kelvin and Tony view such incidents as personal challenges and in no time they managed to crochet a new cod-end using nothing more than a passing bucket, some
Margaret demonstrates the results of shipboard ingenuity

Margaret demonstrates the results of shipboard ingenuity - how to fix a net with some two by fours, a knitting needle and some duct tape - thanks Kelvin and Tony
Photo: Steve Nicol

two-by-fours, a set of thermal underwear and a rivet gun. The result was stunningly effective and Margaret was to be seen this morning, grinning more widely than ever, clutching a brand new appendicularian courtesy of this custom built sampler – this is the sort of teamwork and ingenuity that allowed Scott to succeed, let's have more of it.

Links

CCAMLRKrillWhalesEchosounders - CTD - Map of BROKE-West voyage survey areaPDF


 

This page was last modified on 16 January 2006.