Welcome to my blog.
Here I will post updates about my field trip to South Georgia in the Antarctic Ocean as part of the Southern Ocean Warming (SOW) project. The project is a collaboration between Bangor University and the British Antarctic Survey. The aim is to predict the impact of expected future climate change on Antarctic commercial fisheries and their biodiversity.
These fisheries, normally found in the sea shelf around Antarctic islands, are composed of several species, each of which has their own life history characteristics. In our case, we are most interested in the how long fish larvae stay in a planktonic phase (i.e. drifting with the sea currents) before they settle on the sea bottom. The length of this planktonic phase is important as it will dictate how far away fish larvae will be able to travel from their parents. Long phases will promote lots of mixing of larvae among islands, and hence the fishery for these species can be managed as a single unit. On the other hand, if the planktonic phase is short, then larvae will likely be retained close to their parents with little mixing among islands, and the fishery will need to be managed at an island level. In the last scenario, if an island population is overfished it is unlikely to recover through migration from other islands.
We can estimate the length of the planktonic fish by ageing fish larvae; this can be done by counting daily rings formed in their ear bones. Once we know how long larvae stay in a planktonic stage, we can forecast how far these larvae are likely to reach with the use of oceanographic current models. Then, we can simulate the impact this exchange of larvae will have on population genetic structure among the islands. By comparing these simulated values with real population genetic structure we can evaluate how accurate our models are at estimating current genetic mixing among islands.
Larvae growth rates are affected by their surrounding temperature, and the projected temperature increase in the Antarctic due to climate change, is thus likely to shorten the length of the planktonic phase. This could impact on the larvae exchange among islands, and thus have severe consequences for the fisheries as well as for the species survival at all islands.
In this task of the SOW project, I aim to collect icefish larvae at the beginning of their planktonic phase and keep them in tanks at ambient temperature and at the projected Antarctic temperature in 2050.
Although, this may seem as a simple task, two factors complicate things. First, the highest densities of larvae are during the Antarctic winter, so I have to go there from July to September during the coldest months. And secondly, collecting icefish larvae in a good enough condition to be kept alive is not as simple as it may seem. Icefish larvae can be collected in abundance with plankton nets, but their skin will be damaged by the mesh, and may get squished at the cod end. So I have to use a different approach, with larvae traps that will not damage the larvae and, once retrieved, will keep water in them so the larvae are never exposed to air. To that aim I have come up with a couple of trap designs modified from other models I have seen.
From now on I will be posting every so often about my adventures about getting these traps together, travelling down to King Edward Point in South Georgia, and my experiences with getting the fish larvae and, hopefully, keeping them alive in the aquarium.
Wish me luck, I’ll need plenty of it!!!
And thanks for watching this space!