Hello everyone! There was a question on my last post about how habitat type is discerned and incorporated into our hook and line sampling design. Habitat type is discerned using various underwater camera systems such as sleds, ROVs, and landers. The data received from these deployments are then used to generate habitat type which can subsequently be incorporated into an ArcGIS program. There are also other methods of distinguishing habitat type such as SONAR, LIDAR, and satellite imagery, but I do not know the extent to which these are used for our habitat maps.

Anyway, this past week I again found myself out at sea helping with the hook and line fishing surveys in the Cascade Head Marine Reserve, which is about an hour trip by boat from Depoe Bay. We fished for two consecutive days and caught a wide variety of rock fish and round fish species including: kelp greenling, black rockfish, blue rockfish, lingcod, yellow eye, yellowtail, canary, china, and quillback. The black rockfish and kelp greenling are euthanized and kept for age dating purposes, while the others are quickly released after capture. Fish that suffer from barotrauma are hooked to a descender device and are released at the depth at which they were caught so that their swim bladder can recompress. Some rock fish species are more susceptible to barotrauma than others; blue rock fish are notoriously prone, while others such as kelp greenling and lingcod do not require any assistant at descending to depth.  Although assisting in these hook and line surveys take up the majority of the week, I did find time to assist in another project: benthic extraction.

Benthic extraction is a study of the benthic invertebrate community. It is one way in which marine biodiversity is assessed and quantified. It involves SCUBA divers scraping invertebrates off quarter meter square rock structure and bagging the samples into mesh bags. The samples are then brought to a lab where they are sorted according to phyla and put into sample jars. The samples are then preserved with formalin and sent to an eco-analyst where they are then sorted into lower taxonomical ranks. Species diversity, abundance, and biomass are quantified which will serve as indicators of biodiversity. The goal of benthic extraction is to compare biodiversity between marine reserves and their associated comparison areas to observe how biodiversity and benthic community structure may change over time. This, along with hook and line surveys, are a couple ways to evaluate the effectiveness of Oregon Marine Reserves as a management tool.

I have fallen a bit behind on this week’s blog post, due mainly because of my involvement in intensive field work projects. Although field work is what everyone is dreaming of when they are stuck in the office managing data, it does eventually wear you down physically and mentally. The first half of the week I embarked on the Ann Marie, a local fishing charter vessel, to conduct our first round of hook and line sampling in the Cape Perpetua area. The second half of the week I was down south along Port Orford where I was again performing hook and line surveys out of Red Fish Rocks Marine Reserve. I would wake up at a painful 4 am in order to get down to the docks on time and help load up the boat. Due to heavy winds that generally pick up in the afternoon, we aim for an early start in order to bypass the foul weather. Hook and line surveys are done according to a strict protocol that dictates the exact latitude and longitude, the duration, and the type of terminal gear rigged on each and every fishing rod.  This protocol is also used for hook and line sampling in both California and in Washington State, and with Oregon now on board, the methodology is now standardized across the entire west coast.

This protocol consists of delineating 500m² cells within each marine reserve and comparison areas using ARC GIS. Local knowledge from fishermen is then incorporated into the GIS map, which highlight the best fishing reefs in each area. The areas are then stratified by depth and habitat type and all cells that are deeper than 24 fathoms or exhibit non rocky substrate are excluded from the GIS map. The 24 fathom mark was chosen in order to reduce fish mortality after release; rock fish mortality is compounded by the depth at which they are caught and brought to the surface. Non rocky habitat was excluded because as the name suggests, rock fish are generally only found in rocky habitat, so it is not worth the effort to fish in sandy bottom. Five cells are then randomly selected using a random number generator and each cell is fished for a total time of 45 minutes.

Now that you have an idea about the methodology, it may become apparent that this method is not one that is aimed at catching the most fish in the least amount of time.  The goal is to take a replicable and consistent approach that minimizes possible covariates, which can become a rather nuisance during analysis or create biases in the data. For example, if the duration of fishing in each cell (45 minutes) was not accounted for then our results would be skewed because, theoretically, more fish are caught the longer one is fishing for. However, like many ecological study designs, there are certain variables that can’t be controlled for.

Total catch in each cell varied widely, with some cells pulling in over 50 fish, while others had none. Differences in catch can be explained by a myriad of factors, most notably temperature, habitat, depth, and light. The ocean may exhibit slightly different conditions during any given day which cannot be easily controlled for. Light and temperatures sensors, however, are deployed at each cell which we can correlate during the analysis.

Most of my remaining time here will be spent helping in the hook and line surveys. These surveys will continue for another 2 months after my internship has ended, so unfortunately I won’t be involved in any of the analysis. These surveys are expected to continue every summer for the next 10 years.