NPRB Gulf Of Alaska

In from the Field  Work

by Olav Orsmeth

December 16, 2013

Greetings from an adventure of a different kind- our postseason wrapup. Now that the field work is over, we are faced with two immediate new tasks: dealing with our gear and getting all of our sample analysis lined out.

Just yesterday I went down to the Alaska Marine Lines terminal to pick up our final shipment of gear, barged down from Juneau. Last week we got the bulk of the gear from Kodiak. The first and most important task is to dry everything out- stringing nets to dry, hanging up raingear, and spreading out all the electronics to get any residual moisture out. At the moment our gear room (pictured) looks like a bomb went off inside. Once everything is aired out we will clean, lubricate, and polish, then store things away in preparation for the next field effort (who knows when that will be!).

At the same time we're working on gear, we're also preparing all of our samples for analysis. We have zooplankton samples and fish stomachs in formalin (a preservative), frozen fish for the fatty acid and stable isotope analyses, and fish that we have saved for species identification by our taxonomy experts. We prepared sampling designs for all of these collections before starting the field work but we always collect more samples than we can analyze, because we never quite know what we're going to encounter in the field and how that will affect the ultimate sampling design. So, our challenge now it to asses the spatial and temporal breadth of the samples we were able to collect and revisit the original design. The main limitation is the cost of analyzing samples, as most of the procedures are quite expensive. It's often a trade-off between number of samples and the level of detail we can get from each sample.

For example, our zooplankton samples could be treated in two ways. We could do a basic description, where we identify the organisms to a lower level of taxonomic detail (family or genus rather than to species). Because the time spent per sample would be relatively short, we could analyze all of the samples we collected and have high spatial resolution. We could also take a contrasting approach, in which we identify every organism down to species level. This is time-consuming and would limit the total number of samples we could analyze, but gives us much more valuable information, especially considering that very little sampling has been done in these bays prior to our study. Which one is better?

I talked in a previous post about the question of scale. In the case of zooplankton, our temporal scales are pretty much fixed- we want sufficient samples to make seasonal and interannual comparisons. The question really is the appropriate spatial scale- if we do fewer samples, do we have sufficient spatial resolution to describe the zooplankton community in a bay? How about describing prey fields for young fish?

After wrangling with such problems, it's somewhat of a relief to break off and spend a couple of hours scrubbing out buckets and spraying WD40 on rusty c-clamps. All in a day's work!