A Crabtastic Life

The worst part of being an observer is not the crab shell measuring or living at sea for weeks on end. It is the paperwork. By the end of my two week deployment on a crabbing vessel I had written a small novel containing documentation of every single crab and sea star caught in the sample pots I took every day. This, my dear readers, is science and ecological management at work. Few outside the world of science appreciate the tedious nature of data collection (unless you are an accountant, why do you hate yourself so?), without which science and informed decisions would not be possible. And science is what has allowed the achievements of modern civilization, without which we would still be living in mud huts and hunting with obsidian tipped spears. Regardless of your religious beliefs, god did not identify the fundamental composition of nature, purify it, refine it, and turn it into objects we depend on. I am talking about cars, the fuel that powers the cars, the metal and plastics the car is made of. But that isn’t even the tip of the iceberg. To continue, the food you eat is created using genetic engineering, complex chemical fertilizers, weather forecasting using mathematical models and historical data. The smartphones that connect you to the world uses sophisticated programming and feats of engineering on a nanoscale level. I could go on and on, but suffice it to say literally everything you use on a daily basis is derived and perfected using science. This is possible because of scientists dedicating their lives to collecting data on something they find “fascinating”, “a noble cause”, or with the hope of changing the world, and sometimes for the more frivolous goal of becoming famous. Next time you meet a scientist, thank them for their service to humanity.

While flying back from Dutch Harbor I sat next to a deckhand from one of the Deadliest Catch boats. At one point he asked if killing crab due to counting crabs caught during cold weather was really worth it.

When this happens, he sees wasted crab, time, and money. Understandably this frustrates many fishermen. During this exchange, I’d like to think I was able to communicate how important the data is, no matter the waste. The livelihood of many fishermen in Alaska depend on the Alaskan department of fish and game making wise decisions. The department has a mandate to maximize the amount of crab caught while maintaining a healthy sustainable crab population. In other words, they are told to toe the line between catch all you can and keeping enough crabs around to mate and reproduce. In order to do this they need data on how healthy the crab populations are. Even if this means killing a few. Historically, every major fishery that has been unregulated or even lightly regulated has resulted in over-fishing and the fishery collapsing within a short time. Alaska is no different. In the 1970s and 1980s, The Fish and Game department had poor data collection and analysis methods. This resulted in over exploitation of the fishery and the subsequent population crash left many fishermen jobless and penniless. That’s a big deal when boats and permits cost hundreds of thousands of dollars and living in Alaska isn’t cheap. Since then, fish and game has updated their methods and greatly improved their models. The result has been what is considered one of the healthiest and best managed fisheries in the world. So as much as the fishermen grumble about big government making their lives difficult and being unreasonable, big government is the only thing keeping them from ruining themselves via over-fishing while also doing their best to ensure the fishermen catch a “sustainable” amount. Deep down inside, I think the fishermen know this, they’re just too ornery to admit it.

Even more underappreciated is how difficult it is to assess the health of the crab populations. The Bering Sea is four times the size of California. In the fish and game models that were used when the population crashed, king crab were assumed to be uniformly distributed across the Bering Sea shelf. However, as you will read about later in this post, that is not the case. The question is then: how do you, as biologist, figure out where king crab are and how many? Lets explore some ideas. Scuba Diving Surveys: The crab hang out in deep water, humans aren’t aquatic, high mortality rate. How about GPS/radio tracking tags: King crabs molt at least once a year, meaning any GPS tracking tags would fall off fairly quickly. Ok, fine, a remotely operated submersible to track and count the crab: stupidly expensive. Fish and Game’s solution is hiring desperate fresh-out-of-college biologist as observers to collect catch data and the sketchy National Marine Fisheries Service yearly non-species specific trawl. So you can’t track their movements, you can’t count how many there are, and your models for predicting how the population changes from year to year is based on data sets collected by observers on crabbing boats and a highly suspect yearly trawl. Can you, using this data, assess the health of the fishery? The short answer is “sort of, but not really”. This makes for grumpy fishermen who feel like a bunch of tree huggers are making their job unnecessarily difficult and grumpy biologists who know they have an impossible task but need the job.

As a cog in the machine, my job is just as problematic. I collect data on what the fishermen are catching and also monitor fishermen for “potential” regulation violations. Emphasis on the potential. I am not a crab “cop” and have no authority to write citation. All I can do is document, collect evidence, and tell Fish and Game. So you’d think my job is fairly straight forward. Except when it isn’t. On paper I am supposed to check the crab pots for escapement mechanisms, check for illegally retained crab, etc.

This is kinda difficult when the pots are constantly being used and the crab are being quickly moved to a water filled tank. We are also to make note of any crab or by catch that is left on deck, but the observer determines the definition of “retained”. I, personally, don’t want to make their lives difficult, call it a pragmatic survivalist approach. The crab fishermen are moving constantly, pulling crab pots up, sorting crabs, re-baiting, and dumping the pots back into the water. Sometimes crabs and fish get missed and sit on deck for a few minutes until there is a lull in the chaos. Should I document every time this happens? The critters will be fine if they are put back in water within a “reasonable” amount of time, but I also don’t want the fishermen to think I don’t care so long as it ends up in the water. There are a lot of grey areas and a bit of diplomacy involved in being an observer. The name of my position, “observer”, sums up my existence on fishing boats. I observe. It is kinda like having someone constantly looking over your shoulder for anything you do wrong while also taking what you catch, for science of course. Oh, and also eating your food, sleeping in your bed, asking annoying questions, and getting in your way on deck. I am the most loved person on the boat. You’d expect them to demonstrate their appreciation. I am sure they’d love to, except for the $150,000 fine and several years in prison for harassing an observer. But enough about my job, let me tell you something about crabs.

The cohort

Observer training provides a crash course in crab biology. But all they really teach you is “This is a crab shell. It’s called a carapace. This is how you measure it. Oh, we know how they reproduce, but not really. OK, you are all now crab experts.” It left me feeling a little…..under-educated. Since then I have learned a thing or two more about Lithodes, also known as king crabs.

King crabs are gangsters. After settling out from their planktonic stages, called zoea and megalop, they cluster together on the ocean floor in groups containing up to several thousand. These prickly balls of spines coalesce during the day by climbing on top of each other.

Juvenile King crab pod

It is hypothesized they do this to protect themselves and not just because they enjoy playing king of the hill. But who would want to eat such hard pokey lumps of ornery?
 While they are young and relatively thin shelled, any number of fish such as cod and halibut might take advantage. Once they are mature though, they continue this behavior, which is odd because from what I have gathered from conversations with crab biologists, not much wants to snack on a fully grown king crab. Too much ornery. In the words of one biologist “they are at the top of the benthic food chain”. During the night, they climb down from their spiky collusion and spread out to forage. Divers have noted roaming herds of crabs on the ocean floor, eating detritus and any small critters (sea urchins, worms, etc) that don’t move fast enough. At the end of the night they will reform their pokey blob, sometimes in the same location as the previous night. In a way, they are the carnivorous scavenger cows perusing the bottom of the Bering Sea.

During my time talking to captains in bars, I have heard some interesting bits of fishing lore. One is that the crabs tend to be inactive during a full moon. At first I thought they were either messing with the new observer (me) or it was more fishing lore bullshit (I heard a lot during my salmon fishing days). But maybe it is true.

You might be wondering why, but first a little note about their habitat. Red King Crab (Paralithodes camtschaticus) spend most of their 20–30 years of life on the relatively shallow continental shelf that is called the Bering Shelf. The shelf depth ranges from 50 to 200 feet deep; shallow enough to allow light to penetrate to the bottom and for photosynthesis to occur. This specific geographical feature is one of the major contributing factors to the incredibly rich ecosystem found in the Bering Sea. My Hypothesis for why the crab might hunker down during a full moon is that the light is bright enough to penetrate to the shelf floor and trigger day time podding behavior. Maybe it is also bright enough for larger predators to hunt crab too. They also stay podded during storms. From what the captains in the bars say, it doesn’t stop them from making their crew work 32 hour shifts in 20 ft seas for several days while not catching a single crab. It does, however, make the observers quite happy.

While counting crab I became curious as to how they sense their surroundings. Unfortunately, fishermen and fishery managers interest in king crab perception extends only so far as crab finding their way into a crab pot. That is to say, I could not find any published papers on how they see. Kinda lame… What I do know is they have compound eyes similar those found in insects such as dragonflies. If you want to know more, look it up on Wikipedia.

What about touch? In humans, our skin is embedded with a multitude of tiny nerve endings which sense different properties that we cumulatively perceive as touch. But king crabs do not have pliable skin that allows for easy detection of pressure. So what do king crabs have? If you look closely at the appendages of a crab you will see clusters of hairs. They function much like our own hair. When something touches the hair, the crab feels it.

One slow day on the boat I flipped a king crab on its back and found hundreds of little clusters of hairs on the claws (chelipeds). The chelipeds were drawn toward the crabs mouth. I gentle brushed my fingers across one of the clusters and sure enough, the cheliped responded quickly, moving in the direction I had brushed the hairs from. I tried tapping on the claw, avoiding the hair clusters, and to my surprise it didn’t respond. However, when pushed down against the bench they tried standing up and moving away. There must be some sort of propioception in the muscles which allows the perception of force. What that is, I don’t know. Directly underneath the exoskeleton is a layer of cells which are responsible for maintaining the exoskeleton and also excreting calcium carbonate into the soft protein layer that is present after molting (the scientific term for molting is ecdysis). I am curious if this cell layer might have nerves which allow the crab to sense deflections in the exoskeleton.

An interesting phenomena recently discovered in many marine organisms is bio-fluorescence. When UV light is shown onto certain organisms, they glow. In the ocean, this might be important because water absorbs most wavelengths of light within a few meters of depth.

Glowing hermit crab

More energetic light such as blue, green, and yellow are not as easily adsorbed and penetrate deeper into the water. This is what gives the ocean a blue or green color. It also reduces the ability of organisms to use body coloration to signal. However, one possible way around this limitation is absorbing light and re-emitting it at a different wavelength, aka different color. Charismatic organisms such as Sea Turtles, Sharks, Mantis Shrimp, corals, and many species of bony fish bio-fluoresce. It has also been noted in Hermit crabs. Coincidentally, King crabs are believed to be closely related to Hermit crabs. I am curious if King crabs or other invertebrate species living on the Bering Sea Shelf might also exhibit some form of Bio-fluorescence. I guess I will be taking a UV light with me to the Bering Sea. I hope the only things I find on the fishing boat are glowing crabs. >.>

Macro to microscopic parts of a crustacean exoskeleton

While we are on the topic of crab shells, what is a crab shell exactly? I am glad you asked. Instead of having a hard shell immediately after molting, what would be the shell is instead a protein membrane consisting primarily of chitin. This allows the skin to be permeable and also very pliable. Not ideal if you are trying to protect yourself from other animals and need hard skin in order to flex your muscles and move. Imagine trying to move when your bones are made of rubber, that’s what it is like for a crab right after molting. But it is ideal when trying to squeeze out of your old skin and need to be flexible in order to do that. This also means crabs are particularly vulnerable after molting. Once free of its former shell though, the layer of cells underneath the protein membrane begin excreting calcium carbonate into it, adding rigidity to the membrane and forming what we normally think of as the hard shell. What is the protein membrane? It is a molecule called Chitin which is constructed by connecting glucose molecules into really long chains. That’s right, chitin is sugar. So next time you are eating crab, just remember, the shell is like candy. Candy that can possibly kill you if you don’t chew it well enough or your immune system decides you made a poor life choice (allergic).

Stay tuned for my next post: “Life on the High Seas — Stories from an observer”. I saw fishermen perform inhuman feats of strength, a giant squid fighting for its life, fishing in 100 ft seas, and more. In this next post I reveal all!

Suiting up for the adventure of a lifetime
One clap, two clap, three clap, forty?

By clapping more or less, you can signal to us which stories really stand out.