Sea lions devastating threatened fisheries...

Another article about the devastation sea lions are causing on fish stocks on the west coast.  Only this time, the focus isn't on salmon.  Sea lions have been congregating at passage points on dammed rivers on the west coast for years, and have been consuming salmon as they enter these passages to return upriver to spawn.  This has been in the news for quite some years, since around 2005, and have continued to receive some level of attention in the public eye, where sea lions are being killed to save salmon, even while salmon experts call for other options.It has also received attention in scientific communities,  to the point where large dollars have been invested to examine the exact impacts on salmonid populations by the increase in sea lion and seal populations. 

However, the new article as it appeared today talked about sea lions now beginning to consume female sturgeon as they reach these dam points.  This is a relatively new idea.  It appeared in a Northwest Council report about strategies to address the sturgeon population.  Not sure if this is a prey switching situation, as my recent online search hasn't turned up many results.  But this was a finding in the above report:

"Limiting Factor:  Marine mammal predation

Primary Threat:  Predation by sea lions on sub-adult, adult, and spawning-size white sturgeon below Bonneville Dam.  Oregon and Washington Department of Fish and Wildlife staff have directly observed more that 150 white sturgeon being preyed upon between January 2006 and May 2007, more than 60% of which were spawning-size fish.  These are actual numbers based on direct observations during other sampling activities, not a targeted sampling effort; the actual number of white sturgeon taken by sea lions is likely much higher.  Steller sea lions appear to be especially effective in preying upon large, spawning-size sturgeon, and may selectively capture fish of this size.

Strategy:  Conduct non-lethal hazing actions on the Columbia River to deter California and Steller sea lions from feeding on white sturgeon. 

Measures: Hazing with acoustic and percussive devices, flares, and rubber bullets has been shown to be relatively effective in deterring predation on white sturgeon by Steller sea lions in the area immediately below Bonneville Dam.  Hazing has been an ineffective deterrent for California sea lions.  Steller sea lions have been appearing earlier in the year each year since first sited near Bonneville Dam.  Hazing to protect sturgeon should begin when Steller sea lions are first sited near the dam in each year.  In 2007, hazing began in mid-December from Bonneville Dam downstream approximately six miles to Navigation Marker 85.  Hazing will take place four days a week during daylight hours.  Separate from the hazing efforts, fishery managers from Washington, Oregon and Idaho are seeking federal approval to use lethal means to remove individual California sea lions from below Bonneville Dam that prey on white sturgeon as well as Chinook salmon and steelhead listed for protection under the federal Endangered Species Act (ESA).  Efforts to date have focused on the area immediately below Bonneville Dam, but predation by sea lions on white sturgeon is known to occur throughout the lower Columbia River."

Well back to the article, its brief, but basically it talks about observations of the sea lions eating sturgeon on the Columbia River.   And while this isn't being observed at the Fraser River yet, given the still increasing sea lion and seal populations, its probably only a matter of time.

The impacts of top predator declines...

(My best shark photo, sorry!)
So I check out Underwater Times from time to time to see whats new in the underwater news world.  So when I happened upon this article from the United Arab Emirates, it reminded me of a Science paper that came out a few years back that is near and dear to my heart.  But first, the news article.  Essentially, sharks are a major fishery in the Arabian Gulf.  From 1985 to 2000, shark landings in the UAE ranged from 1350 to 1900 tons of sharks, and the UAE is a major exporter of shark fins to Asia.  However, scientists and fishermen alike have started to notice that the loss of shark predators has impacted the ecology of the Arabian Gulf.  This has lead to a study to be undertaken examining these impacts.

In the article, a sentence mentions how the loss of sharks on the Atlantic coasts has lead to a collapse in bay scallops.  So you guessed right, this is where the 2007 Science paper which I find so particularly fascinating comes in.  This paper, entitled "Cascading Effects of the Loss of Apex Predatory Sharks from a Coastal Ocean," by the late Ransom Myers and others detailed a study whose base conclusion was that the loss of sharks due to overfishing cascaded down the food web and resulted in the loss of bay scallops in North Carolina.  They examined fisheries data for trends in individual species of elasmobranchs, the family of fishes to which sharks belong, from 1970-2005 between Cape Cod, MA and Cape Canaveral, FL.  They were able to demonstrate strong decreasing trends in  the abundance of great sharks, which are the apex predators.  Over the same 35 year period, the populations of smaller elasmobranchs, including smaller sharks, skates and rays, were shown to be increasing.  Many of these species, and the cownose ray in particular, are known consumers of benthic prey, including a variety of shellfish.  In North Carolina, cownose rays move into the estuaries to feed in the summer, and were capable of removing entire bay scallop populations before they could spawn, and decimating populations to a point that densities were so low, that successful fertilization could not take place.  By 2004, the North Carolina scallop fishery was gone.  These mesopredators are also likely to be impacting the recovery of other shellfish species through consumption. Thus, the loss of sharks, even through by-catch, is likely to have devastating ecosystem impacts, not just in North Carolina, but likely in many coastal areas. (For other reasons why sharks matter, check out this website, this cool blog called Ya Like Dags, and the ongoing series of shark posts over on Southern Fried Science).

Myers RA, Baum JK, Shepherd TD, Powers SP, & Peterson CH (2007). Cascading effects of the loss of apex predatory sharks from a coastal ocean. Science (New York, N.Y.), 315 (5820), 1846-50 PMID: 17395829

Another paper that came out of the Charles Peterson group (he was a co-author on the above Science paper) investigated restoration options for scallops in North Carolina.  Obviously, cownose rays still prevent a major problem.  One mode of restoration they examined was a way to protect adult scallops in a spawner sanctuary from predation by the rays.  They were able to accomplish this via a fairly simple method of using PVC stakes into the sediment that reached out of the water at high tide, evenly spaced narrowly enough so that the rays could not fit inside.  This method was capable of successfully maintaining dense populations of adult scallops during the period when the rays were in the estuary.  Obviously, allowing populations of adults to survive to spawning is a major step in enhancing scallop populations.

Stephen R. Fegley,* Charles H. Peterson, Nathan R. Geraldi and David W. Gaskill (2009). Enhancing the Potential for Population Recovery: Restoration Options for Bay Scallop Populations, Argopecten irradians concentricus, in North Carolina Journal of Shellfish Research, 28 (3), 477-489 : 10.2983/035.028.0309

Nature Blog Network

I just joined onto the Nature Blog Network.  Its a cool site that compiles all nature-type blogs that are members.  It has many categories, including some that I find particularly interesting, including Marine, Mollusks, Invertebrates, and Photography.
Check it out!

Gelatinous zoop!

There is an interesting blog over on discovermagazine.com about the way sea walnuts (or ctenophores, or Mnemiopsis leidyi) feed (in addition to a cool video, which is posted below).  Apparently, these organisms use their cilia to create almost undetectable currents, and they are then capable of catching unsuspecting prey with great efficiency.  Due to their incredible ability to feed stealthily and efficiently, they have been particularly devastating invaders in European water bodies.  When these comb jellies showed up in the Black Sea, they contributed to a food web collapse by consuming many of the fish larvae that would typically serve as the base of the food chain.  In fact, gelatinous zooplankton are often considered productivity dead-ends; they consume productivity in the forms of other plankton, however, they offer little food value to other species.  So the productivity is not transferred to other trophic levels, and food webs collapse.  This is also becoming a problem in human impacted systems.






This blog made me remember some research some colleagues at the School of Marine and Atmospheric Science conducted.  PhD student Marianne McNamara, under the tutelage of Darcy Lonsdale, investigated the impact of high abundances of ctenophores on larval bivalve mortality.  
In their article "Shifting abundance of the ctenophore Mnemiopsis leidyi and the implications for larval bivalve mortality," published earlier this year in Marine Biology, McNamara et al investigated how ctenophore abundance has changed, their digestion rates, and finally, their ability to control bivalve larvae.  The data from this article is of particular importance for the hard clam restoration and management effort in Great South Bay, NY (their field sites), since the comb jellies may exert a strong predation pressure on hard clam larvae.
They conducted field surveys to investigate the abundance of ctenophores and other zooplankton.  They enumerated and took volumetric measurements of the comb jellies, then looked at their gut contents. Finally, they conducted lab feeding experiments, and then used equations to calculate their ability to control bivalve larvae.
McNamara et al found high densities of ctenophores in the early summer, and larger ctenophores in the late summer, and when compared to the literature, densities were considerably higher than in previous decades.  This is of particular importance, since bivalve veligers made up approximately 63% of the ctenophores' gut contents, indicating this is a particularly valuable food source for the jellies.  In addition, using their equations from densities and feeding rates, they predicted that at peak abundances, the ctenophores could consume over 94% of the bivalve veligers in Great South Bay.  This is a particularly alarming figure.  In addition, the peak abundances of ctenophores occurs earlier in the year (early summer) now than it did decades ago (in the fall), putting peak abundances of comb jellies in the water column at the same time as the bivalve larvae.
Clearly, this study illustrates the potential ecosystem impacts of increasing gelatinous zooplankton.  While they have already been shown to be particularly harmful as invaders, it is now apparent that they can have impacts where they are native as well.  It is likely that increasing human impacts leading to pelagic dominated production will lead to more ctenophores in coastal systems, which can prevent benthos from reestablishing in these areas.  This might be the case in Great South Bay, where the hard clam populations are struggling to recover despite the Nature Conservancy's efforts at replenishing them.  Now I don't know about their high end estimates, as one could imagine if ctenophores were capable of consuming essentially all of the bivalve veligers, then veligers and comb jellies wouldn't be collected together in plankton tows.  However, it is clear that ctenophores can possibly have a major impact on a local ecosystem.

McNamara, M., Lonsdale, D., & Cerrato, R. (2009). Shifting abundance of the ctenophore Mnemiopsis leidyi and the implications for larval bivalve mortality Marine Biology, 157 (2), 401-412 DOI: 10.1007/s00227-009-1327-6

The Great Flood is coming!!!!

If you live in a certain part of North Dakota, that is.  I have only been to North Dakota once (for the NJCL conference), so I have limited experience.  But I imagine its a very nice place with very nice people.  Well I came across this AP article about a place called Devil's Lake, North Dakota.  Apparently, this lake is an endpoint for local water run-off; that is, it has no drainage, no natural rivers or streams allowing the water that accumulates from rain and snowmelt to flow out of the lake.  So this lake has been growing over the past few decades, getting deeper and larger in size.  Since 1990, 400 houses have been moved or destroyed due to the rising waters.  Small towns are in danger of becoming inundated, while others were essentially bought out in entirety, by state and federal governments and are now submerged.  The waters have risen so high in recent years that the lake is only 6 feet from overflowing, which would be devastating to many downstream towns and communities.  A breach of the flood banks would send water into communities near and far, with estimates of flooding exceeding any previous floods.  There is considerable debate about what to do with the problem.  But for right now, residents just wait for the slow moving devastation.

If nothing else, check out the article here.  It has a really cool animated graphic showing the lake in the 1980s and the lake today. 

I am famous!

Well, not really, but I can dream right?

There as an article in the latest issue of the Suffolk Times ( a local east end newspaper) about hard clams in Hallock Bay.

Now, the basic summary of the article is that a group of local baymen had raised some money to plant seed hard clams in Hallock Bay, NY. If you have followed my blog at all, then the name Hallock Bay should sound familiar to you - its the location of one of my dissertation projects and a place I spend a lot of time in the water (and here, and here). Anyway, back to the article. The baymen released 85,000 8-month old notata clams - about the size of a thumbnail - into a portion of Hallock Bay. They selected a bottom with considerable cobble as their planting area in the hopes that the structure will protect the juveniles from their predators like whelks and crabs.

First, it is exciting to hear about local baymen - commercial fishermen who often get a bad rap when it comes to preserving marine species - trying to do something to help the bay. Some of the original scallop restoration efforts were started by baymen. But the most interesting and exciting part of this article for me was the 8th paragraph:
"The fishermen agreed that Hallocks Bay is a good spot for clamming, but they pointed to a broad swath of coastline, opposite the grounds they were seeding, that has been closed for two years -- not because of poor water quality but because of a study Stony Brook University students are doing to see if they can simulate eelgrass bed habitats with synthetic eelgrass."

That's me! While the project isn't exactly described right, and I am not mentioned by name, it is still quite exciting to see my work in the paper, regardless of how small or anonymous.

Fishes respond poorly to seagrass loss

Well it has been a few weeks since I've posted on some research articles. But then the Journal of Experimental Marine Biology and Ecology published a manuscript about cod responses to expanding seagrass meadows. In addition, a paper out of Japan earlier this year talks about the loss of fish species with the loss of an eelgrass meadow. Combined, these point out the obvious, many finfish are dependent on seagrasses for habitat. However, its not just typical seagrass-associated species that are affected by the loss of seagrass.

First, what happens when seagrasses disappear? There is a wealth of literature that suggests disappearing seagrasses has many negative consequences for both resident and transient species. Many species, including numerous commercially important species, utilize seagrass as a habitat for at least some portion of their life cycle. A paper by Yohei Nakumura examining seagrasses next to l reefs demonstrated that seagrass loss has an impact on the abundance and diversity of fishes, including reef associated species. A series of disturbances, particularly typhoons, decimated a seagrass meadow near a reef, to the point where in 2009, the seagrass meadow had totally disappeared. This caused a 80% reduction in the number of species and a 90% reduction in the total number of individual fish along transects at the same site before and after the disappearance. In addition, they monitored a nearby undisturbed site as a reference, and there was no difference in the abundance or diversity of fishes over the same time period. Many of the fishes that disappeared weren't just seagrass residents, but also coral dwellers. In fact, the only species that didn't seem affected were some gobies. The reason for the loss of fish might not be the eelgrass itself, although the habitat does provide shelter from predators, but could also be due to loss of food for many of the fish - tiny crustaceans that live amongst the seagrass.

A more recent paper involves the increase in abundance of juvenile cod in areas where seagrass is recovering and expanding. First, I know what you are all thinking, I love cod and eelgrass associations! And second, it is great news to hear that seagrass is recovering in some areas (I can talk more about this later). Apparently, there are seagrass meadows in Newfoundland, Canada, that are recovering and expanding over the past decade. These habitats are nursery grounds for both Atlantic cod and Greenland cod. So, one might imagine that an increase in seagrass would be beneficial to these species. Using biweekly seines to monitor changes in fish abundance, Warren and others were able to demonstrate dramatic increases in young of the year cod in the seagrass habitats, in particularly in those "recovering" habitats. This increase also occurred rapidly with expanding seagrass meadows. This suggests that these fish are capable of recovering quite quickly if enough suitable habitat exists. However, it also suggests that since juvenile cod might respond so rapidly, that any negative changes in seagrass cover can be detrimental to stocks. Combined with the Japanese study, the literature indicates that fish populations may lack resiliency to seagrass loss, and illustrate the need for water quality monitoring and management, as well as seagrass restoration. Otherwise, the news that cod stocks might recover, might be just internet fodder.

Nakamura, Y. (2010). Patterns in fish response to seagrass bed loss at the southern Ryukyu Islands, Japan Marine Biology DOI: 10.1007/s00227-010-1504-7

Warren, M., Gregory, R., Laurel, B., & Snelgrove, P. (2010). Increasing density of juvenile Atlantic (Gadus morhua) and Greenland cod (G. ogac) in association with spatial expansion and recovery of eelgrass (Zostera marina) in a coastal nursery habitat Journal of Experimental Marine Biology and Ecology DOI: 10.1016/j.jembe.2010.08.011

Some videos

So I've been following some other marine science related blogs recently, and Mike over at Cephalove often posts videos, and I thought I would check to see what kinds of videos of bay scallops are available on the internet. I came across these three, which I will share today, which actually talk specifically about the restoration program on Long Island which I am a part of... enjoy!

This first video goes through the hatchery process:



This is the second part of the video, where the news team goes out on the barge and sees the other side of the scallop project:


The final video of the day is just another look at the longlines:

A brief video on the Scallop long lines in Orient Harbor from Cornell Marine Program on Vimeo.

Shrimp, anyone?

There is some speculation about the FDA's standards for Gulf seafood. Granted, I know the government wants to do everything it can to restore the economy to this oil-ravaged region. According to some recent posts, the FDA may be allowing higher PAH levels in shrimp, crabs and oysters sold for consumption, because they assume that most people in the US don't eat very much seafood in a month, and that the majority eat significantly more finfish than shellfish. It appears as though the new concentrations for BaPe for shellfish in the Gulf is 3x higher than the levels allowed in other recent oil spills. In addition, some lab testing not done by the FDA suggest that the levels of PAH in the shellfish is much higher than this allowable limit. Of course, this calls to questions differences in methods for testing, but there might be some cause for concern here. We all heard about the sniff test method.

It speaks volumes when even the fisherman are questioning the reopening of the Gulf fisheries. Sure, we all like a shrimp cocktail now and then, but is it possible the FDA, under pressure from state and federal government, lowered safety standards to try to bring some revenue back into this part of the country? I'd like to think things don't work that way, but I don't know. I will look for a more reputable source for this news, but when I saw this, I thought it might be worth mentioning.

Link Dump

Figured I would try something new today, dump a couple of interesting links:

Today, you can read about aquanauts living on the seafloor studying sponges off the Florida coast

Learn about jellyfish and their increasing abundances

How WWII impacted North Sea fish stocks and the implications for marine protected areas in management of cold water species

An angler who set the world record by catching 1000 different fish species

And check my out on twitter, I'm a newbie though...

Looks like we might be spared...

Here on the East End of Long Island, I was concerned towards the beginning of the week about the impending Hurricane Earl. At that point, it seemed like it might be headed toward us. Of course, I was most concerned with my field experiments, which I can not stop, and then started to think about the overall impacts of hurricanes on the benthos.

From the literature research, it seems as though estuaries are particularly resilient to the impacts of major storms, and in particular, estuaries which frequently experience these issues. Granted, Long Island is not a site of major tropical weather, we do get out fair share of severe weather in the forms of Nor'easters. As a matter of fact, a major nor'easter hit Long Island, New York and New Jersey in March 2010, which brought sustained 60mph winds and gusts up to 73 mph (hurricane force winds are 75mph).

So I started to become less worried. Now I just hope that my experiments can handle any associated surge with the storm, and that all my cages and blocks are still out there next week!