All that said, during one of my field excursions a particularly large spiny dogfish coughed up something during capture that I frankly have never seen before and haven’t been able to find in any ID books.  It is pretty well-digested, but intact enough that it looks like some kind of fish.  It’s about 10 cm long, and the dogfish that ate it was caught in the vicinity of Atlantic Beach, North Carolina.  Check out the image below the jump, any help you can provide with ID would be appreciated.

Seriously, what the hell is this thing?

When providing ID help, please be sure to note the date of this post.

This round of field work is part of an NC Sea Grant Fisheries Resource Grant (FRG) project, which means we work with commercial fishermen to answer questions relevant to fisheries science.  This is a great program that goes a long way towards bridging the divide between commercial fishermen and researchers: it allows fishermen to participate directly in the science and scientists to make use of the fishers’ knowledge of local waters.

In this case we were working with frequent Rulifson lab collaborator Chris, a commercial gillnetter out of Hatteras.  Chris normally fishes for monkfish and dogfish,but this time took us to a few spots in the Hatteras Bight that local fishermen have been trying to avoid due to the high number of “biters” in the area.  Hatteras fishermen classify sharks as either “dogs,” smooth and spiny dogfish, or “biters,” which are usually small or juvenile Carcharhinid sharks.  The local names get more detailed than this, with species-specific names such as “white-dotters” for Atlantic sharpnose sharks (because the adults have white spots) and “circle biters” for small sandbar sharks (because they can tear circle-shaped holes in your rain gear if you make the mistake of only holding them by the tail).  Chris has been fishing for decades and knows a ton about the things that swim by the Cape at any given time of year.

Chris really put us on the sharks.  In two days of sampling, we caught and measured 180 juvenile sandbar sharks, 4 sharpnose sharks, two dusky sharks, one smooth dogfish, and one 6-foot scalloped hammerhead.  Three angel sharks, some false albacore, and two of the largest shad I’ve ever seen also made appearances.  Of those sharks, 15 sandbars and one dusky are now carrying acoustic tags and will hopefully show up on our array and others deployed along the Atlantic coast, providing crucial data on their migration routes.

That’s the science.  Here are the pictures.

The sheer number of juvenile sandbar sharks off of Cape Hatteras has to be seen to be believed. The only other sharks I’ve ever seen come up in comparable numbers are spiny dogfish.

This is the picture I wanted to take all summer. Of course moisture somehow got inside the lens and blurred me out. At least the shark is clear, and the sharks are the real stars anyway.

The first time surgically implanting and acoustic transmitter is a harrowing experience. Fortunately Andrea, veteran of dozens of surgeries on spiny dogfish, was there to coach me through it. My first couple surgeries took about 20 minutes, his took about five. Most importantly, all sharks subjected to the procedure survived.

Dusky sharks are a species of concern for NOAA.  Their slow growth and late maturity, as well as the ease of mistaking them for species legal to land, are causing them to recover from overfishing at a snail’s pace. On the flipside of that extreme life history, they’re born enormous. This nearly 4-foot female is not far off from size at birth for this species.

Sandbar sharks are an especially hardy species and were generally good candidates for the surgeries. We were less sure about the dusky and stuck around to ensure a healthy release. Though disoriented at first, she soon picked up speed and began swimming more confidently. She then began taking some frustration out on the gulls and pelicans that had gathered in hopes we’d be tossing something more manageable overboard.

Atlantic angel shark. Not a target species, but a cool catch nonetheless. Don’t underestimate their ability to suddenly lunge at your face off the deck of a boat.

Not a shark, but still a cool fish. These false albacore, also known as little tunny, were running in the area. These small tuna are probably a staple of the diet of Cape Hatteras’ larger sharks.

Atlantic sharpnose sharks are usually the most common shark in the area in the warmer months, though the unseasonably warm water (about 64 F on the bottom) brought a few adults of this species to our nets.

Another adult shark was this scalloped hammerhead, checking in at just over six feet in length. This is another species that isn’t common off of Cape Hatteras in the winter.

The hammerhead had apparently lead a rough life before we caught it. Its jaw may have been damaged by an earlier encounter with a longline or tuna charter.

All in all, a pretty successful trip.  I’m looking forward to seeing where our tagged sharks go, and hope to add more sharks to the roster soon.

So what does this mean for Ya Like Dags?  Well, this blog will continue to exist as it has for 2.75 years now, as a remora attached to the larger fish that is Southern Fried Science.  And like the mighty dogfish, it will adapt.  While my “big-picture” posts on fisheries management and general-interest marine biology will go up at the parent blog, field work recaps and shorter, observational posts will continue to appear here.  So really, if you want the full Dags experience you’ll have to follow both blogs.

As always, thanks for reading and if you’re the rare reader that isn’t also regularly reading the parent blog, I hope you’ll join me there too.

Cape Hatteras is well-known as the “graveyard of the Atlantic” for its ability to eat boats.  The same geographic and meteorological quirks that make the Hatteras Bight so treacherous for boats also make it a brutal environment for scientific gear.  The high-flyer buoys and anchoring systems we use to keep the acoustic receivers in place are built to take some serious punishment, and still our rate of gear loss is much higher than we’d like.  To make matters more interesting, the work involved in recovering the data and deploying the array requires lifting and manipulating heavy objects by boat.  This means we need to wait for decent weather in order to safely accomplish a deployment.  Anyone who’s ever worked around Hatteras will tell you that “decent weather” is very rare in that part of the ocean.  On top of all that, our latest trips took place after a little storm named Sandy.

Now that you’ve read through the educational part, it’s time for the photo dump:

That’s the top of the high-flyer buoy poking out of the water. There are literally enough biofouling creatures on there to almost sink the entire buoy.

A small selection of the biofouling community that builds up over only a few short months. Invertebrate fans would have a field day with the sheer number of sessile organisms that make use of our “artificial reefs.”

This is what one of the receivers looks like after 3-5 months under water.

Not all the critters hanging out on our array are sessile. This adorable little bugger made a home in the weighted end of one of the high-flyers.

This octopus managed to get under the concrete anchor and make a nest. I felt kind of bad about disrupting it.

After Sandy, this high-flyer was battered but still standing strong.

When the buoys break off, we have to send divers down to find the rest. Believe it or not, we usually do.

It’s not just ocotpi moving in when our gear ends up on the bottom. If you look closely, this crab has a sea anemone for a hat.

Note how this buoy looks crushed. We recovered this high-flyer off the bottom after Sandy. The hypothesis is that huge storm waves pulled the high-flyer under so fast that the pressure crushed the buoyancy out of the buoy.

Never a dull moment off of Cape Hatteras.

Big Fish Expeditions, a series of dive operations focusing on sharks and other charismatic marine megafauna run by shark photographer extraordinaire Andy Murch, is offering a dive off the coast of my home state of Rhode Island.  This dive includes two days with the blue sharks and shortfin makos that have been getting some attention off the coast of New England, and a previously untried subject of ecotourism, the spiny dogfish.

The next big thing in shark diving? Image by Andy Murch (elasmodiver.com).

According to the description of the trip, after two days free-diving in blue water with blues and makos, divers will be taken to an offshore wreck where, hopefully, hoards of spiny and smooth dogfish will be chummed in.  Unfortunately I can’t afford $975 and travel costs on a PhD stipend, otherwise I would already be signed up.  I could always use more diving in my life, and the idea of being surrounded by a massive school of tenacious little sharks strikes me as unbelievably awesome.  Hopefully other divers feel the same.

I’ve seen dogfish feeding and swarming from boats before, and from that I know these little guys can be pretty charismatic.  Could dogfish dives become a viable economic use of this species?  I suppose we’ll find out after the first dives this summer.

Experimental setup from Frid et al. (2012). Arrows in the top image point to fishes trying not to be “seen” by the fake lingcod, while the bottom image shows a kelp greenling dashing in for the prize.

Predation affects animals both directly (by being eaten or doing the eating) and indirectly, usually through behavior intended to minimize the risk of being eaten.  Frid et al. (2012) wanted to see whether the degree of risk-taking or risk-avoiding behavior in kelp forest fishes varied by species.  To test this, they set up bait stations using tethered shrimp in reef areas in Howe Sound (near Vancouver), and placed a fiberglass replica of a lingcod, a large predatory fish that functions as a high-level predator in Pacific Northwest kelp ecosystems.  They then set up a camera and observed the behavior of the fish checking out the bait.  What they found was that antipredator behavior trumped feeding in long-lived, slow-growing species such as rockfish, while faster-growing species like kelp greenling were more likely to risk being eaten to snatch up the bait.  This is a trend seen very generally in nature.  Since longer-lived species have to survive longer in order to reach the point where they can reproduce, they tend to be more risk-averse.  Conversely, life is “cheaper” for the more r-selected species, and some of these species may need to prioritize food over safety in order to fuel their fast life cycles.  In the case of these fish, this study implies that a reduction in predator numbers (like the lingcod) may make life easier for juvenile rockfish, which are important from both a conservation and fisheries standpoint.  Whether that’s worth increasing fishing effort on lingcod is another matter, but this is the kind of information managers need when trying to manage the fishery at an ecosystem level.

Now we get to sharks.  Sharks, even the smaller species, tend to be upper-level predators wherever they are, and as such may have important effects on the behavior of their prey.  Hammerschlag et al. (2012) used satellite tagging of both bull sharks and tarpon (a very popular gamefish) to determine whether the paths of these big fish cross.  It’s well-known that large sharks prey on tarpon (particularly if the tarpon are already hooked), but does that affect the movement patterns of these big-scaled fish?  It turns out that tarpon definitely show evidence of avoidance behavior, avoiding habitat overlap with the sharks whenever possible.  Also, when the fish have to cross areas where large sharks occur, they move in straight lines as fast as they can until they make it to cover.  There’s always a bigger fish…

Sometimes information on feeding habits is found completely by accident.  In a previous post, I summarized a paper about satellite-tagged fish being eaten by sharks, which actually showed up in the data logged by those tags.  Beguer-Pon et al. (2012) had this happen to them when they deployed archival tags on American eels migrating out of the St. Lawrence River.  Tags from six of their eels showed a sudden increase in ambient temperature and changes in dive profile, giving away that they were eaten by a warm-bodied fish.  By comparing the gut temperature and dive profiles to those recorded for porbeagle sharks and bluefin tuna (gut temperature was too cold for a mammal, and these are the two warm-bodied fish predators in the area), they were able to figure out that their eels had been eaten by porbeagles.  Tagging data from porbeagles themselves show that the sharks make long-distance migrations to the Sargasso Sea, and area of the Atlantic Ocean off the southeastern U.S. that also happens to be where eels migrate to spawn.  Could the sharks be following the eels?

Sharks don’t just eat fish.  Reptiles, birds, and marine mammals are all on the menu, and so are other sharks.  The great hammerhead is notorious for eating other elasmobranchs, and Mourier et al. (2012) documented an epic attack by one of these sharks on a school of juvenile grey reef sharks.  The hammerhead swooped in and snatched up one of the smaller sharks, and in response the entire school reef sharks gave chase.  The predatory behavior must have been awesome to witness (and Mourier et al. did get some good pictures) but even more interesting is the mobbing behavior shown by the reef sharks.  Most schooling fishes are totally fine with their buddies getting eaten instead of them and concentrate on getting away, but these sharks took off after their own predator, putting themselves at risk and exhibiting behavior typically seen in social birds and mammals.  Was this simply an attempt to drive away their predator, or was this actually a rescue attempt?  It is known that some sharks form strong social bonds, and reef sharks form especially strong ones.  While it’s impossible to know the true motivation behind the chase, it’s certainly interesting.

A great hammerhead swoops in for the kill, slashing through a school of grey reef sharks (top image) and making off with one unfortunate shark, though its schoolmates can be seen in hot pursuit (bottom image). From Mourier et al. (2012).

I’ve said it before and I’ll say it again.  Predation is awesome.

Sources

Béguer-Pon, M., Benchetrit, J., Castonguay, M., Aarestrup, K., Campana, S., Stokesbury, M., & Dodson, J. (2012). Shark Predation on Migrating Adult American Eels (Anguilla rostrata) in the Gulf of St. Lawrence PLoS ONE, 7 (10) DOI: 10.1371/journal.pone.0046830

Frid, A., Marliave, J., & Heithaus, M. (2012). Interspecific Variation in Life History Relates to Antipredator Decisions by Marine Mesopredators on Temperate Reefs PLoS ONE, 7 (6) DOI: 10.1371/journal.pone.0040083

Hammerschlag, N., Luo, J., Irschick, D., & Ault, J. (2012). A Comparison of Spatial and Movement Patterns between Sympatric Predators: Bull Sharks (Carcharhinus leucas) and Atlantic Tarpon (Megalops atlanticus) PLoS ONE, 7 (9) DOI: 10.1371/journal.pone.0045958

Mourier, J., Planes, S., & Buray, N. (2012). Trophic interactions at the top of the coral reef food chain Coral Reefs DOI: 10.1007/s00338-012-0976-y

The proposed changes to the commercial fishery aren’t too radical, and represent measures that scientists have been in favor of for a while.  Basically, NFMS is looking to break up the old “fishery complex” scheme in which most shark species are grouped as either large or small coastal sharks and quotas are assigned for the species as a group.  This creates problems because not all sharks in the group have the same growth and birth rates, so not all species in the complex can handle the same level of fishing.

To fix this, NMFS has been conducting species-specific stock assessments on shark species and is proposing breaking some species out of the fishery complexes to be managed on their own.  These include the large hammerheads, blacknose sharks, and blacktip sharks form the Gulf of Mexico (an assessment of the Atlantic stock is still in progress).  These species would be given their own separate quotas, and the severely declining large hammerheads would be given a very low one in the hopes of curbing overfishing.  With scalloped hammerheads proposed for listing on the Endangered Species Act, this should take some of the pressure off of the species from the general coastal shark fishery, and will also allow the agency to monitor the situation for hammerheads specifically.

The next big proposal for the commercial fishery is the establishment of a series of time-area closures to reduce longline effort in areas important to sensitive species, especially the dusky shark.  Essentially, fishing won’t be allowed in these areas at times when these patches of ocean are important as nursery habitat or migratory corridors for duskies.  Some closures already exist, and the new rules would reduce the size of some existing areas while adding new ones in the northern end of the dusky range, reflecting new information on dusky shark habits.

Current and proposed longline time-area closures for the shark fishery. Image from NMFS.

One of the biggest, most obvious proposed changes (and one that’s already gotten some press) is a dramatic increase in the recreational size limit for coastal sharks.  Again, this is largely to protect dusky sharks, which have the unfortunate combination of occurring in many of the same areas where other sharks are fished and a much slower growth rate.  Currently, the recreational size limit is 4 1/2 feet, which is within the size at maturity for many coastal sharks such as blacktips and sharpnoses, but way under the size at maturity for dusky sharks.  NMFS is proposing increasing the recreational size limit to an impressive 8 feet.  This makes some sense for the recreational shark fishery, which is largely a trophy fishery, but may create some issues for charter operators specializing in sharks.

The issue is that the coastal shark rec fishery is dependent on the blacktip shark, which is one of the species doing alright under the latest stock assessments.  Blacktips also very rarely get larger than 6 feet in length, meaning that under the proposed size limit blacktips couldn’t be kept at all (I have it on good authority that blacktip is actually pretty good, so sharks landed in the recreational fishery aren’t usually wasted).  In order to survive under the proposed rules, the recreational shark fishery would likely have to become a strictly catch-and-release fishery.  From an ecological standpoint, this is ideal, but it still represents a shift in business practices for charter operators.  That said, purely catch-and-release fisheries can still be an economic driver (adult red drum in North Carolina are a good example) and some shark tournaments have already made this shift.

So why not have species-specific recreational limits for sharks?  While this may be possible at some point, dusky sharks are just about the most nondescript-looking shark in the ocean.  These sharks can be very difficult to tell apart from other, less ecologically-sensitive species, especially for recreational fishermen who may not be as familiar with species ID.  In fact, misidentification is probably the biggest threat to dusky sharks (landing the species has been prohibited since 1999, so it’s unlikely that anyone is actually targeting them).  By increasing the size limit to 8 feet, even misidentified immature duskies should be protected.

This “161 lb blacktip shark” is actually a dusky. Image from hooked-in.com.

These are currently only proposed rules and are the NMFS-preferred options, though generally I find these to be positive steps.  The full list with all the biological information leading to them is available here, and public comments can be submitted to NMFS until February 2013 (instructions for submission at the bottom of the document).

When looking at these three management stories, it’s important to remember the concept of shifting baselines.  Essentially, the longer ecosystems (in this case marine) are impacted by humans, the more their impacted state becomes considered “normal” and the bar is gradually lowered for what constitutes a “healthy” ecosystem.  This appears to be happening in Florida waters, where the recovery of the critically-endangered Goliath grouper is leading to calls to cull the big fish before they start cutting into the population of spiny lobsters.  Never mind that research shows that these groupers eat mid-sized predatory fish that eat lobsters (therefore indirectly helping the lobster stock), or that the lobster population did not change significantly in response to the crash of grouper numbers (suggesting that the groupers have no direct predatory effect on the crustaceans), or that Goliath groupers may potentially be able to help out with the lionfish problem.  They’re a large predatory fish that is increasing in numbers, therefore they must be throwing the ecosystem off balance.  This is because Florida’s natural marine ecosystem, which in its less-impacted state included plenty of Goliaths, is something that many Florida fishermen haven’t seen in a while.

They’re eatin’ our looooobs! Image from bio.fsu.edu.

This being Ya Like Dags?, you knew this was going in a dogfish-related direction eventually.  Conservative management policies were put in place to avert a dogfish stock collapse in the late 1990s and the stock was declared rebuilt in 2010.  Since then, quotas have consistently been bumped up by the New England and Mid-Atlantic Fishery Management Councils and this year the fishery actually became the second shark fishery ever to be certified as sustainable by the Marine Stewardship Council.  The latest round of quota increases, proposed by the MAFMC, would bring the annual quota up to 40.8 million pounds, and increase the daily trip limit to 4,000 pounds.  To put this in perspective, this is less than 20 million pounds under the quota that caused the dogfish population to show signs of overfishing in the ’90s.  Interestingly, this increase isn’t supported by some dogfishermen, who argue that an increased quota without the processing facilities to support it will just flood the market and drive the price of dogfish down.  However, these fishermen are being countered by fishermen from outside the dogfish fishery, who support the increase on the logic that anything that hurts the dogfish population will help the population of their target species.  The push for increased quota in this case is less about the rational arguments for increasing fishery efficiency and more about culling dogfish in the hopes that this will allow the “right” fish to recover.

Ecosystem-based managment? Image by Sara Mirabilio, from spinydogfish.org.

Perhaps the most egregious example is a story broken by Dave earlier this month.  In the NEFMC’s annual meeting summary, the Groundfish Advisory Panel recommends, among other relatively reasonable things, that the council needs to “find a legal way to kill more elasmobranchs.”  Wow.  Even if Dave’s interpretation is correct and this is meant to reference dogfishes and skates, this is tantamount to declaring a cull against an entire group of species.  If this were simply calling for an increase in bycatch allowance, I would think it would be phrased as such.  With this wide-open and frankly creepy wording, this recommendation could refer to any elasmobranch, even protected species such as a sand tigers and great whites.  This is definitely one of the more worrisome things I’ve seen in a fishery management document, and it deserves all the scrutiny it can get.

All of these incidents point to a misunderstanding of the very nature of ecosystem-based management.  In these cases managers appear to be taking a “reduce this, then that will increase” approach, in which certain “chosen” species are carefully managed while their potential competitors and predators are given a “kill ‘em all” treatment.  While there is some evidence that overfishing may have unbalanced the relationships between some species, those relationships are still too poorly understood to start picking winners and losers.  That isn’t ecosystem-based management, it’s ecosystem manipulation.

The mighty cod stocks that helped drive the settlement of the Northeastern United States didn’t exist in a vacuum.  They were supported by and supported an entire ecosystem that included herring, copepods, other groundfish, dogfish, large sharks, seals, and everything else with an ecological connection to the area.  A healthy fish stock is shaped as much by its competitors and predators as it is by its prey.  This is why single-species management has had such a mixed record of success.  If we as scientists, fishermen, and managers are serious about ecosystem-based management, we need to be serious about the importance of every part of that ecosystem, not try to game it to favor a handful of species.

Which was stupid.  My problems are ultimately “first-world problems.”  Rough patches happen to everyone and are practically a requirement for getting through grad school.  The only way to get through them is to continue finding ways to enjoy the time spent riding them out.  This blog is a part of my grad school/young scientist experience that I not only enjoy, but actually have some control over.  With that in mind, I’m forcing myself to start regularly putting stuff up here again.  Expect at least two new posts this week, and that’s a pace I will try to keep up going forward.  I have a pretty good backlog of papers and management issues I’ve been meaning to write about, as well as an overdue field work recap or two.

This concludes my public apology and expression of feelings.  Keep checking in for more small shark science.  I may have something new up as soon as this evening…