Tag Archives: Crabs

An Update from the South Coast

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A lot has happened since my last post. This week alone I have worked on an ODFW lamprey assessment by electrofishing Winchester Creek’s headwaters, participated in a Sea Grant funded eel grass monitoring survey, and seined for juvenile fish with visiting scientists from OSU. Most importantly, I have successfully completed all of my crab sampling in the South Slough Research Reserve. After deploying 160 traps, I processed over 2,100 crabs in just 12 days. Of these only 86 were the invasive green crabs I was targeting.

Though I had wished to collected more data on the species, my mentor and her colleagues were pleased with my results. I found green crabs in locations they have never been found before. My data also indicates the highest abundance of these crabs in the Coos estuary in the last 19 years. I am currently collaborating with a professor from OSU to publish a report on the status of the European Green Crab along Oregon’s Coast. Please enjoy the pictures below taken on my last day of sampling.

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Crustacean Examination

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After successfully deploying 23 pit traps in the last week (one went missing), on the 7th we were able to check them after being open for 24 hours. The results were pleasing to see, as we did in fact have crabs of multiple species in all of our traps. Many sculpin were caught as well and were noted. The number of Hemigrapsus crabs seemed to increase as we got closer to shore and the number of Dungeness was less and more randomly distributed. We also found two strange looking crabs that turned out to be Pea crabs. As planned the size selection method worked in a fairly smooth manner. I say fairly, because the majority of the traps caught small crabs, but a few actually caught large crabs that we are unsure of as to how they managed to get in. (while molted soft enough to squeeze??). This will be repeated several more times as the summer continues on.

Here is a video of the Dungeness Crab GoPro footage that was shot a few weeks back. We believe the crab is exhibiting this behavior because he (it is a male) is trying to crack his own shell open so that he may begin molting. The video is sped up from 30fps to 120fps.

https://www.facebook.com/austin.r.prechtel/videos/10207203552717977/?l=3251973081910911355

Pit trap in action

Removing the zip ties on a trap to access the catch.

Staghorn sculpins that were caught in the traps

 

The panoramic camera work is taking a bit longer than expected, mostly because some equipment we were thought to of had by now, has not arrived so that testing our design is not possible yet. I have been working with a few video editing softwares that allow panoramas to be made via stitching.

This weekend a trip up to The Gorge is being made. Will post pictures!

Week 2: Dungeness Crab in the Lab

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Week 2 has ended and I have to say that Oregon is becoming more and more homely. Friends are being made and new experiences are occurring. Early in the week, core samples were taken in order to capture mud shrimp. A core sample, to those of you unaware of what that is, is where you take a large metal tube and press it completely into the ground and then proceed to dig all of the sediment out and sift through it while for mud shrimp. To get the core into the ground you must stand on top of it and do the “shrimp dance” which consists of wobbling motions. Once the mud shrimp were captured we measured the carapace length, sexed them, and checked for the infestation of parasites. The parasites are definitely not the most appealing creatures to look at, but they are still very interesting.

The mudflats show no mercy to those who science.

Mid-week many bucket lids were purchased (24 total). The reasoning for this is that we began to build experimental pit traps that would be size selective for the capture of small Dungeness crabs. We made two different designs, one with a larger whole and steeper funnel, and the other with a smaller hole and more gradual funneling. To set these traps, you basically just dig a hole in the ground and place the bucket in and wait for the crabs to fall in. Some people around here call them the “Dodos of the sea”. This is not due to having a resemblance with birds, but because of their ease of capture. After setting the traps we decided to place GoPro cameras onto two of the traps to capture some footage and observe the crab’s interactions with the traps. I’ve taken a brief look at the footage and there is some interesting behavior to note. I will definitely be including some of the video in my next blog entry. Several crabs were captured overnight, as well as a few Staghorn Sculpins, and a lone jellyfish. The next step will be to build 24 traps in total, and set them out in various locations. I’m really looking forward to see how things will play out with the implementation of our traps.

Young Dungeness crab captured in the pit traps

It’s been only two weeks and I already feel like I’ve learned quite a lot. Being from a freshwater background, marine and estuarine has offered a new perspective. 8 more weeks to go!

From Cornfields to Coastal Mudflats

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It has been roughly 12 days since I departed on my 4 day cross-country road trip from Indiana to the coast of Oregon. Many sites were seen like Medicine Bow, Winnemucca Mountain, and Crater Lake. Taking the time to see such colossal structures really made me realize how small we are in the vastness of our own country, let alone the planet.
It took 35+ hours to get to Oregon, and I’ve only been here for roughly a week, but I already feel a sense of home here. For the next 9 weeks, to my understanding, I will be working with integrating different pit trap methods for the capture of juvenile Dungeness crabs (Cancer magister) as well as the utility of using underwater video to get quality quantitative data on fish and invertebrate use of US West Coast intertidal estuarine habitats. Working this week with the USDA under my mentors, I have been very fortunate to already be getting out into the field.

 

Dungeness Crab (Cancer magister) caught from pit trap

This week we drove 60 miles north to Netarts, OR and checked shell bags for colonization by shellfish. We also took water quality in areas that were bare (lacked vegetation) and areas with seagrass present. Closer by (Yaquina Bay), pit traps were set up for the capture of Dungeness crabs to quantify their morphometrics to create more accurate size selection in the future. To our delight, we managed to catch several crabs, along with a few mud shrimp.

Mud shrimp that was dug up with the traps

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

There is no doubt that the next 9 weeks will pass by quickly, a lot will be learned and a lot of great memories are to be made. With that I hope you continue to enjoy my blogging as the weeks go by. I’m lucky to call this beautiful city and state my home for the summer. Follow me on here or via twitter @Prechtelguy93

Prozac project changes

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When I last checked in, I had just begun a pilot study that would assess how shell thickness in mussels may be affected by exposure to Prozac. Unfortunately, the experiment was a bust, mostly owing to the impractical housing conditions which stressed the animals and led to high mortality. I quickly scrapped this project, with the intention of returning to it as a side project sometime later next year. My new focus will still assess the affects of prozac on marine life, but from a completely different angle: animal behavior.

I’d like to introduce this new project by telling you how I came up with the idea. While visiting Netarts, Nehalem, and Yaquina Bay, I noticed the abundance of shore crabs living in the estuary and that they reside primarily in soft sediments, mud, and beneath rocks, never too far from the water margin. This struck me as another creature that may be at risk from contaminants as they are transported from waters upstream and adsorb onto the sediments. I wondered if these crabs were in contaminated estuaries, how would their behavior change and how would this influence food web dynamics. To my knowledge, this is a somewhat unexplored connection linking contaminants as an agent to potentially influence shifts in food webs. We often hear about bioaccumulation of contaminants up the food web, but what if contaminants also affect the behavior of animals and cause them to be more or less susceptible to predation because of abnormal behavior?

The shore crab Hemigrapsus oregonensis, has been extensively studied and their behaviors have been well documented. My aim was to assess whether crabs exposed to Prozac at  3 and 30ng/L (i.e. documented concentrations in estuaries) would be more at risk of predation when compared to unexposed crabs. Because Prozac is a psychoactive drug, it is likely that their behavior will be altered at even low levels with persistent exposure. I am conducting this experiment by creating simulated estuary habitats in 30 tanks (10 replicates for each treatment) with rocky substrate and hideouts to allow for normal predator escape/evasion behavior. We will be dosing the shore crabs every 10 days with Prozac to simulate pulse events (e.g. increased rainfall) into the estuary. The meat of the study will be the addition of the predator, the Red rock crab, to the shore crab tanks and assessing the response to the predator during the behavioral trials, which will last ~1hr. We will run these behavioral trials during the day and at night to see observe their reactions. This project will run from June 1-August 15.

We have already had the animals living in our estuary mesocosms since June 1 and we will be conducting the first set of  behavioral trials next week. More developments to follow. I’m very excited about this study and I believe it is important to explore how contaminants might affect wildlife in Oregon’s estuaries should we

Week 4: Self-Directed Accomplishment

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This week I was supposed to be on a trip with my lab in Willapa Bay, Washington, doing field work. My foot is not healed enough that I was comfortable to go, so I had to sit this one out. I was able to go to the doctor and get an x-ray and my pinky toe is definitely fractured. This means another month of healing, which is basically my whole summer. The silver lining of the situation is that my injury lined up nicely with my move to a new house, allowing me to take it easy while still getting things done, like unpacking and getting settled. My injury means that I had to miss out on the fun and the other people in the lab have to do a lot more work to do, but we’re trying to make the best of it. I should be able to go on the next one though, which leaves this upcoming Friday!

Although I can’t go in the field, I have still been useful doing computer and lab work, which I had a lot of this week. My mentor wanted to give me something hands-on to do, so instead of processing some samples in the field like they normally would do, they brought them back in Ziploc bags so I could process them in the lab. These samples were from the mud and eelgrass areas near some bags of oyster shells that were put out a couple months ago, when Dungeness crabs were recruiting (metamorphosing from larvae into juveniles). The oyster shells create three-dimensional habitat at low tide, attracting crabs seeking shelter and providing suitable habitat for . We periodically sample the bags and some of the sediment underneath, as well as areas nearby with no bags, to look at the number and size of any crabs we find, which are mainly Dungeness (Metacarcinus magister) and shore crabs (Hemigrapsus spp.). This data helps my mentor look at the recruitment and growth of juvenile Dungeness, as well as their preferred habitats. In the lab, I sorted bags of eelgrass, measuring crabs I found and weighing the eelgrass both wet and after drying in an oven.

Because everyone was gone this week, I was responsible for my own success in getting things done, but I think I did a very good job. It helps that I am so used to being in school, where you set your own schedule. I’ve learned a lot of time management, and it’s good to know that this helps in the real world too!

I’m not sure what this next week has in store for me, but I’m definitely looking forward to going to Washington on Friday!