Tuesday, May 31, 2011

Ghost Fishing

friendly ghost fishing?

Recently Virginia budgeted $3.5 million for a Marine Debris Removal Program in an effort to clean their waters of lost crab pots. These “ghost” pots, so called because they continue to trap and kill animals without their attending fishermen, were targeted as part of a larger ($15 million) project to restore the blue crab (Callinectes sapidus) population. What resulted was a 70-[water]man-effort pulling 24,859 crab pots from Chesapeake Bay and its tributaries over the past 3 years! In addition, 3,336 peeler and eel pots and 152 nets were removed.

Chesapeake Bay: red dots are buoyed crab pots,
peach dots are unbuoyed crab pots;

All the pots were located using side-scan sonar tracking. Fishermen who had been shut out of the crab dredge fishery, which had been closed in 2008, were offered the pot retrieval work, making this program not only help the benthic population but also the human population of Virginia.

a pile of pots

In both my work on a lobster boat in Long Island Sound and commercial fishing vessels in the Bering Sea, ghost fishing pots were hard to avoid. Bering Sea fishermen regularly find crab pots, lost due to storms or lines being cut from propellers or ice flows. When a pot was found, it was brought on board, the netting was cut so nothing else could be caught, and then it would be dumped at set locations where other fishermen throughout the Bering know to avoid (pretty neat, actually).

Bering Sea crab pot stuck in our net

Ghost fishing can be a huge problem for both healthy and recovering stocks; VIMS scientists supervising the Chesapeake Bay program estimated that each derelict pot can capture about 50 crabs each year it’s lost! Just within the last year of the Marine Debris Removal Program, 9,970 ghost pots were snagged with more than 11,000 animals trapped inside. Imagine how many animals will be saved, for future stocks and future managed harvests, now that the Chesapeake is without more than 28,000 pots!

dead blue crabs in a derelict pot

Friday, May 27, 2011

Classy lady

My friend Janelle sent me this and I thought it was a lovely follow-up to this post:

from www.nataliedee.com (warning, some of her cartoons feature colorful language)

I tell you what, I did feel pretty classy in Sherry Tamone's crab hat!

Tuesday, May 24, 2011

So bitter!

What makes a crab bitter? Is it the lack of contact with its parents after hatching? Is it the constant diet of polychaete worms (I mean, really, who would enjoy that?)? Oh no, it’s something much worse:

Hematodinium sp.
aka the parasitic dinoflagellate that causes bitter crab disease (BCD).

Hematodinium perezi in blue crab (Callinectes sapidus) hemolymph

This nasty phytoplankton infects crabs, destroying the hemocytes (blood cells) in the host's hemolymph which leads to respiratory and organ failure, and finally death. You can tell if you have a bitter crab by their cooked appearance: Chionoecetes bairdi look bright red and C. opilio look milky whitish yellow. The name “bitter crab” (referred to as both disease and syndrome) comes from the bitter flavor of the infected crab’s meat (Taylor and Khan, 1995). The mechanism behind the spread of BCD is unknown, but may happen during molting, cannibalism, or even just physical contact with other diseased hosts.

comparing C. bairdi:
top was infected with BCD (note the milky-colored hemolymph)
while the bottom was healthy

Recently, Mullowney et al. (2011) investigated possible factors of what may be regulating BCD transmission in Newfoundland and Labrador opies. What they found is that BCD may be density-regulated for snow crabs, meaning that the number of crabs in a given area correlated with the prevalence of BCD in that population. In this study’s case, the density-dependence was influenced by small to medium new-shell (recently molted) crabs. Does the newly molted status mean infection happens during molting? They didn’t say. We’ll have to stay tuned on that one.

comparing C. opilio:
the top crab was healthy while
the bottom was infected with BCD (note the opaque color)

Mullowney et al. (2011) did note that the idea of measuring prevalence of BCD in a population is a tricky thing. It is possible to underestimate prevalence due to inefficient fishing techniques and the ability to only diagnose chronic cases of infection. Overestimation of prevalence can occur through those infected crabs seeking out pots (and the accompanying bait) more so than healthy crabs due to the extra nutritional demands the infection is putting on their little crab bodies.

an eyestalk-ablated C. bairdi from the Tamone lab
potentially infected with BCD (from this article)

BCD is on the rise (remember the velvet swimming crab deaths in France, mentioned here?), and the infection’s resulting mortality is affecting commercial stocks’ reproductive potentiontial. Siddeek et al. (2010) observed BCD and the way it may alter harvest strategies for C. bairdi in Alaska (Sherry Tamone presented on the proportion of BCD in Tanners from southeast Alaska here). Hopefully biologists can learn more about how this disease is transmitted and how it’s affecting populations to better manage our crab stocks!

Read more:
Mullowney, D. R., E. G. Dawe, J. F. Morado, and R. J. Cawthorn. 2011. Sources of variability in prevalence and distribution of bitter crab disease in snow crab (Chionoecetes opilio) along the northeast coast of Newfoundland. ICES Journal of Marine Science 68: 463-471.

Siddeek, M. S. M., J. Zheng, J. F. Morado, G. H. Kruse, and W. R. Bechtol. 2010. Effect of bitter crab disease on rebuilding in Alaska Tanner crab stocks. ICES Journal of Marine Science 67: 2027-2032.

Taylor, D. M., and R. A. Khan. 1995. Observations on the occurence of Hematodinium sp. (Dinoflagellata: Syndinidae), the causative agent of bitter crab disease in Newfoundland snow crab (Chionoecetes opilio). Journal of Invertebrate Pathology 65: 283-288.

Thursday, May 19, 2011

Ask a Grad Student: Laurinda Marcello

Laurinda is a master's student working not only with fisheries in Alaska, but also reaching across our neighbors to the east and looking at the Gulf of St. Lawrence and the Newfoundland/Labrador Shelf! Oh, and she practices karate, so watch out!

Age: 26

Degree: MS, Fisheries

Current City: Juneau

1. Describe your project, in 4 sentences or less.

My research is part of a larger project looking at interactions between gadoid fishes and crustaceans in Sub-Arctic areas (Ecosystem Studies of Sub-Arctic Seas working group 4). I’m using regression models to look at things from the perspective of one crustacean: snow crab. I want to know how environmental conditions, spawning stock biomass, and predation by gadoid fishes influence snow crab early life history. Finally, I’m comparing results across several ecosystems to learn whether snow crab recruitment is governed by the same principles across areas or not.

Pacific cod: "Get into my belly!"

2. What was the most surprising result of your model?

The relationship between snow crab spawners and later recruitment was surprising. You would think that more adult crab means more offspring, right? Well, when I looked at models I didn’t see that. Sometimes spawners didn’t matter at all. Other times, higher spawning stock biomass resulted in lower recruitment. I have some ideas on why that might happen, but I’ll save that for my talk.

3. You don’t work directly with crabs but have you had any field work on other projects? If not, is there anything you’d like to do/work on in the field?

I previously worked for Sitka Tribe of Alaska monitoring sockeye salmon at the Salmon Lake weir. A coworker and I would tag each sockeye, take scale samples, and record its length and gender. We also tallied the other salmon and trout species passing though the weir and kept a daily log of environmental conditions. A few times during the season our bosses would come to the lake so we could run a beach seine (to better estimate population size using mark-recapture methods).

Salmon Lake weir

sampling the sockeye (Oncorhynchus nerka)

It was a nice change of pace to be outdoors for the better part of the summer. I was living in a wall tent so there was a lot to do besides counting fish. Every week or two we would hike then boat to town for groceries and fuel. During my free time I liked to take pictures, fish for trout, watch brown bears, and play cards.

home sweet home

In the future I would definitely love to land a job that gets me out on the water or trekking through the woods on a regular basis. I know I’ll have to spend a lot of time at a desk, but I’d like to do field work again.

view from Salmon Lake: definitely beats an office!

4. You grew up in Alaska. If you could live anywhere else, where would it be?

I really love Sitka and intend to move back there. But you know what? Hawaii is really nice too: ocean, mountains, rain, and cool people. I could see myself in a small town or rural area like Hana.

5. What is your favorite piece of crab paraphernalia? If not crabby, then ocean-themed paraphernalia?

My jar of sand from Sandy Beach in Sitka. I’ve been carting the thing around with me since I first left for college.

a sweet sandy momento

Thanks Laurinda!

Thursday, May 12, 2011

My own personal crab spy

My sister Emma Yanevskyy is a super-sleuth of crabby paraphernalia. She has a shop on etsy (shameless promotion? Maybe.) so she spends a fair amount of time checking on it and meandering other shops to check out the competition. When she finds something of the crustacean persuasion, she sends it my way (including the crab sign from this post)! Here are some of my favorite crabby things she’s found on the interwebs:

"Now everyone is on the beach!"
found here

he might be signaling a turn, but then again, you never know with fiddler crabs
found here

who doesn't want a pillow with an octopus-baby hybrid munching on a whole lobster?
found here

Please enjoy the benefits of my personal crab spy!

Monday, May 9, 2011

Attennnnn - TION!

Back in March I read an exciting and sad article about a new crab species. I wanted to wait until the genetic results came back before reporting to you, but I just got too impatient.

Meet the newest soldier crab:

Do you recognize this soldier crab? Neither did the scientists on a Thailand crab survey!

The “new” species of giant soldier crab was discovered in Satun province, Thailand (maybe). Puntip Wisespongpand of Kasetsart University, chief researcher on a crab survey led in the Satun, Nakhon Si Thammarat, and Songkhla provinces, found the unfamiliar crabs and sent them away for DNA analysis (hence all the waiting in new-species anticipation!). A new crab may not be too shocking for Thailand, proud home of about 800 crab species, but this small soldier (carapace width ~ 14 mm) is already fighting for survival. The potentially new crab was discovered at the future sight of a potential deep sea port, the Pak Bara Beach; the deep sea port at Pak Bara Beach is slated for expansion of the petrochemical industry in southern Thailand.

circled: Satun Province, Thailand
(Bangkok is starred for reference)

Bummer, right? Until we know for sure if it’s a new crab species, and we see what happens with the Pak Bara Beach, let’s learn some more about soldier crabs in general. (Ha, get it? General soldier crab info??)

• Soldier crabs have their own taxonomic family: Mictyridae (genus = Mictyris)

• They are filter feeders, thriving on mud flats and beaches where they can filter the sand for interstitial fauna and detritus

• Their feeding behavior results in hundreds of little sandy balls during low tide, similar to the sand bubbler crabs featured on Blue Planet!

If you know any more information about this new crab, feel free to comment!

Thursday, May 5, 2011

Another Day of Miscellany

1. Did you know you can do this on "gchat" (or whatever... you know what I mean)? I didn't either (thanks, Courtney)! Just type in V.v.V and watch the magic happen!

me annoying my husband

2. The Snow Crab Love logo has a fan in Laine Welch and Pacific Fishing (the business magazine for fishermen)! It was featured in an article about the most recent Bering Sea snow crab season. No links were available to connect readers back here, but now you know! (And you can check out their website here.)

3. Do you doodle? I do... dle. (Ha!)

Get it? Like the Incredible Hulk??

And now in color (thanks, Photoshop):

(Of course, no one in my lab would throw crabs around, or react so violently if that were to occur. We're all very friendly. Just felt the need to point that out.)

Monday, May 2, 2011

Baby boom

I can track the search words people use when coming to Snow Crab Love and saw the question:

How many babies can a snow crab mother have?

Ahahaha! I love this kid's expression!
(picture from here)

I feel bad that the reader didn't get the answer they were looking for, so here goes:

Conan et al. (1989) estimated that snow crab females can produce between 31,000 and 90,500 orange eggs in one clutch. The top number drops slightly, to 88,800, when considering brown eggs (embryos that are further along in development) due to egg loss. (Read about the different colors of development here.)

eyed snow crab emryos attached to their mom

Similarly, Comeau et al. (1999) estimated 88,500 brown eggs within a large (85 mm carapace width) female's clutch, and for smaller females (55 mm carapace width) they estimated 31,500 eggs. Their study showed that fecundity for female snow crabs is positively correlated with carapace width (or size), which isn't too shocking. The egg estimations were based off of subsamples of clutches that were back-calculated to get the full clutch number (using a ratio of dry weight of 250 sampled eggs to the dry weight of the full clutch). Their study differed in that they thought large females may start out with as many as 116,000 orange eggs! This difference suggests greater egg loss during development.

full uneyed snow crab clutch = THOUSANDS of potential baby crabs

Females may lose eggs within their clutch due to some eggs remaining unfertilized, developmental problems, predation, or parasitism. Loss due to unfertilized eggs is why I'm concerned with male snow crab gonads: we want to make sure each male is giving the females he mates with enough sperm to fertilize at least one whole clutch.

These estimates don't include loss after hatching due to predation, cannibalism, and other problems (which accounts for a huge proportion of snow crab mortality), but this should give you an idea of how many babies a female can produce.

Fecundity Findings:
Comeau, M., M. Starr, G. Y. Conan, G. Robichaud, and J.-C. Therriault. Fecundity and duration of egg incubation for multiparous female snow crabs (Chionoecetes opilio) in the fjord of Bonne Bay, Newfoundland. Canadian Journal of Fisheries and Aquatic Sciences 56: 1088 - 1095.

Conan, G. Y., M. Moriyasu, D. R. Maynard, and Y. Chiasson. 1989. Factors influencing egg production in decapod Crustacea with two case studies: Chionoecetes opilio and Homarus americanus in the Gulf of St. Lawrence. ICES CM 1989/Mini 04.