So anyone following my blog knows that I was actively involved in the bay scallop restoration efforts in Long Island. To refresh, scallop populations supported a vibrant fishery in NY until the mid 1980s, when populations crashed due to the first occurrence of a brown tide bloom, and recurrent brown tides pushed scallops to the brink of local extinction. The brown tide has not occurred in the Peconic Estuary since 1995 (although it still occurs on Long Island waters), so in 2006, restoration efforts started to help jump-start local scallop populations in the Peconics.
Commercial bay scallop landings and Brown tide occurrence
These efforts sought to boost spawning stock and concentrate high densities of scallops in close proximity to enhance fertilization and reproductive success. The idea was that low population densities of adults were limiting reproduction, which was subsequently limiting larval supply and recruitment. The restoration efforts sought to boost adult populations by establishing spawner sanctuaries using an array of lantern nets or by high density on bottom restoration. You can watch a number of videos on these efforts here, or watch the Fox News piece below:
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The restoration efforts had been very successful – every year we see higher numbers of scallop spat than the year before (despite the same effort), and the results have translated to scallops on the bottom and to the fishery. Recently, our group was able to publish some of our findings in Marine Ecology Progress Series.
We were able to demonstrate at all sites annual increases in the mean spat per bag – that means, each year post-restoration, we saw greater numbers of baby scallops in our collectors. This occurred not only in our basins where we actively did restoration, such as Orient Harbor and Hallock Bay, but also in nearby basins with no active restoration efforts, such as Northwest Harbor.
A figure from our MEPS paper, illustrating the annually increasing densities of scallop spat in Orient Harbor. The cross denotes the site of a large lantern net spawner sanctuary.
In fact, scallop spat abundance increased up to 3000% of pre-restoration levels. This was despite that none of the environmental parameters had changed from the 10 years prior to restoration beginning to the 5 post-restoration years we examined for this study. Environmental variables could possibly influence the amount of larvae produced and larval survival. However, temperature, chlorophyll (a proxy for food), nitrogen, monthly rainfall and salinity were not different between the 2 time periods. This suggests that the restoration efforts played an important role in helping to increase the larval availability. In essence, we “primed the larva pump!”
Environmental variables for the pre-restoration period (1996-2006) and the post-restoration period (2007-2010).
Obviously, we were expecting these results and were very excited that we were able to eliminate other possibilities of increased larval supply. Additionally, the dates of peak settlement for the most part lined up with our estimates of spawning dates and settlement.
This doesn’t mean much, however, if it isn’t translating to the bottom, since we collect these scallops in spat collectors hanging in the water column. Many sources of mortality, but primarily predation, can occur from the time the scallop settles on the bottom to the time it can spawn and then contribute to the fishery. I focused most of my dissertation research on habitat and predation on scallops. Some of the cool things from that research suggests that patchy seagrass might not be detrimental to scallop populations and that an invasive species might be a suitable alternative habitat. So, despite limited seagrass in our restoration estuary, we have seen increases in scallops on the bottom.
On bottom increases in scallop densities post restoration
And in many of the basins, these increases in on bottom densities in the fall correlates with the increases in spat fall during the spring of that same year.
Relationship between seed scallop densities in the fall on the bottom in Orient Harbor and the spat per bag landings from the spring.
We are currently preparing this data for a manuscript, showing the subsequent increases in on bottom densities, fishery yield and the economic benefits of the restoration efforts. Hopefully, the success of this project and the information gathered will help other restoration efforts on Long Island, such as the Shinnecock Bay Restoration Project (which I have blogged about ) and elsewhere. I am hoping to turn some of the things I learned with this project (and the many various side projects) to my oyster work here in NC, although I also plan to keep working with scallops.
Or – What do I do when field observations don’t match lab results. This is a philosophical debate that has plagued ecologists for decades and it brings up all sorts of issues – relevant scale, extrapolation, replication and pseudoreplication, variable control, realism, and the list can go on and on. How did I arrive at the crux of this debate?Cochlodinium polykrikoides. It is a harmful algal species, now a common annual occurrence in Long Island, NY, whose blooms are known to be ichtyotoxic, and more recently, to be potentially devastating to shellfish as well. Now I am not a harmful algae person by any stretch of the imagination, but many of my colleagues are, and I often find myself engaged in healthy debates with them over the utility of lab vs field experiments.
Image from Chris Gobler
Why? Well there is a body of literature that suggests C. polykrikoides is harmful to a number of shellfish species. In fact, chronic exposure in the lab has led to high mortality and depressed growth rates of juvenile bivalves. Other studies demonstrate rapid mortality of bivalve larvae in lab exposures over periods as short as 24 hours. Lab experiments have proved especially useful in determining the mechanism of toxicity, and determining how dense blooms should be to have particularly devastating impacts. The Gobler lab at the School of Marine and Atmospheric Sciences at Stony Brook University is at the forefront of many of these studies.
Again, I am not a harmful algae person, so why do I care about this? Well, my study organism, the bay scallop, can be affected by these blooms. That, and the fact that millions of dollars have been invested to restore bay scallop populations in NY waters. The earliest research of these blooms out of New York (where they first appeared in 2002 and have recurred annually since 2004) indicated harm for bay scallops. Using 5-l plastic buckets and bloom water collected from the field, Gobler and others (2008) demonstrated up to 75% mortality of juvenile scallops (~11mm shell height) after 9 days of exposure. Additionally, this stud demonstrated a significant impact on scallop growth rates, being half in the bloom water as in controls – so even those scallops that survived were not doing well.
Other studies out of the lab have showed something even worse – up to 100% mortality of scallop larvae over relatively short time scales during the lab study. In well plates, Gobler and Tang utilized 10 ml of varying bloom densities of C. polykrikoides or a control consisting of T-Iso (Tahitian isochrysis) . In this study, with 20 larvae in each 10-ml well, the highest CP cell densities, >2000 per ml, caused rapid 100% mortality of bay scallops, within 10-24 hours. This is clearly problematic, as blooms occur when scallop larvae are expected to be in the water, so this has potential to be devastating to the restoration effort.
Figures from Gobler et al 2008 and Tang and Gobler 2009
If we extrapolate based on these results, we would expect extremely low recruitment and abundance of bay scallops. In fact, the Gobler et al paper from 2008 says exactly that: “Our results demonstrate that the failure of this population to recover could be due, in part, to recent outbreaks of C. polykrikoides blooms in this system.” Wow. Has that for scaling up! What’s the problem here? Well, first and foremost, the statement is fundamentally false. Anyone who has been following this blog can attest to the fact that scallop populations are indeed recovering. The most recent literature shows over 13-fold increases in on bottom densities of scallops in restored basins – see Tettelbach and Smith, 2009. And a manuscript we are currently finishing shows even better results. Landings have been increasing as well, as demonstrated here:
Data from Steve Tettelbach
In addition, as an unexpected natural experiment of sorts this summer, I was able to observe scallop recruitment in the presence of C. polykrikoides, which means the scallop larvae survived, remained competent, settled, grew, and survived all in the presence of this harmful algal blooms. This is preliminary data still, and remember, I was not looking for this relationship. In fact, I was simply interested in monitoring scallop recruitment in Shinnecock Bay, a south shore lagoon, with healthy eelgrass populations (and eelgrass is the preferred scallop habitat, although other habitats are also important). That was my goal. Being interested in all things, I thought it would be useful to have an idea of size fractionated chlorophyll analysis for each of my Shinnecock Bay study sites, to see what the differences might be across the bay. Additionally, I collected water that I fixed with Lugol’s so I could have an idea what the phytoplankton community looked like. As a part of this process, I was able to get CP cell densities at the same sites which I collected scallop recruits.
So what gives? Well, I think that its clear that lab experiments can’t be so easily extrapolated to the ecosystem level. And maybe, we shouldn’t even attempt to extrapolate these data to ecosystem scale processes. Lab experiments are good because they are extremely reproducible, can rapidly generate data, regulate all independent variables, and are lend toward easy replication. However, they have limitations in both spatial and temporal scale, realism and generality. So while larvae in 10 ml of high concentrations of CP all die within 24 hours in the lab, the likelihood that that kind of exposure happens in the field is extremely unlikely. Even the 5-l bucket experiments were unrealistic. The lab experiments failed to incorporate physical and biological characteristics of the system. Things such as larval availability, larval behavior, algal behavior, water column depth, variations in temperature, daylight, salinity, the community, etc, are all ignored in the lab experiments.
However, by its very nature, CP is difficult to study in the field. It is a spatially aggregating, chain forming species – so that over the spatial extent of the bloom you can experience cell densities that vary by orders of magnitude. It also undergoes diel vertical migration, so that it is at the surface during the day and the bottom at night (where exactly they go at the bottom is another story). It just can’t be controlled in the field and its spatial extent and bloom density is highly variable and unpredictable. So figuring out the problems with the lab exposures is not as simple as placing some scallops out in the field. So its a question that is not easily solved, which is probably why it is still being debated after decades.
Image from C. Gobler
In case you couldn’t tell, I am a field ecologist by trade, so I am obviously a little biased. But I do personally believe that lab experiments, while important, have limited utility in ecological studies without appropriately scaled field studies to corroborate the results. Many times, microcosm studies don’t. I am not as bullish on lab studies as Stephen Carpenter (1996) who suggests “an ecologist who isolates organisms in bottles may not be working on communities and ecosystems in any relevant sense.” I think that microcosms and lab experiments have their place – and that they provide valuable information for ecological studies, and I do employ them on a limited basis. It is just in my strong opinion that their value becomes limited without field testing the results.
Either way, it is certainly an interesting debate. Both sides have valid arguments – reproducibility, replication, control in lab experiments, the realism, relevant scales, and generality in field and natural experiments. The ideal combination of lab and field experiments depends on the questions asked and species studies. But it is clear that at times, the field observations don’t match what would be expected from lab experiments. This doesn’t mean either side is wrong, but illustrates the need to utilize both practices.
EDIT – This blog post is not intended to suggest harmful algae don’t have impacts in the field. There are plenty of examples from the field of harmful algae having impacts on fauna – including the recent sardine die-off in California. Rather, it is only to illustrate disconnects between field and lab observations.
Carpenter, S. (1996). Microcosm Experiments have Limited Relevance for Community and Ecosystem Ecology Ecology, 77 (3) DOI: 10.2307/2265490 Gobler, C., Berry, D., Anderson, O., Burson, A., Koch, F., Rodgers, B., Moore, L., Goleski, J., Allam, B., Bowser, P., Tang, Y., & Nuzzi, R. (2008). Characterization, dynamics, and ecological impacts of harmful Cochlodinium polykrikoides blooms on eastern Long Island, NY, USA Harmful Algae, 7 (3), 293-307 DOI: 10.1016/j.hal.2007.12.006 Tang, Y., & Gobler, C. (2009). Cochlodinium polykrikoides blooms and clonal isolates from the northwest Atlantic coast cause rapid mortality in larvae of multiple bivalve species Marine Biology, 156 (12), 2601-2611 DOI: 10.1007/s00227-009-1285-z Tettelbach, S., & Smith, C. (2009). Bay Scallop Restoration in New York Ecological Restoration, 27 (1), 20-22 DOI: 10.3368/er.27.1.20
New species get introduced into novel habitats almost like clockwork in the modern era. These are termed introduced or exotic species. Typically, these introductions are the effect of anthropogenic activity. Sometimes, these species become nuisances – spreading in their new habitats via natural processes, and creating problems for native species. These nuisance exotics are called invasive species.
So how do they get here? From a variety of ways, but perhaps most famously via ships’ ballast dumping. Ballast is simply material used by ships to control and maintain buoyancy and stability. Typically this is water, pumped into ballast tanks from the port the ship is sitting in at the time. This ballast water gets pumped in or out depending on the weight of the cargo on this ship, and so you can imagine how water could be transferred across whole oceans, bringing with it any species that happened to get sucked in to the ballast tank. This is a major source of marine invaders – including the now infamous zebra mussel, Dreissena polymorpha, which has become especially problematic throughout fresh waters of the Mississippi River, the Great Lakes, and the east coast. However, invasives can also come from aquaculture gear and species – especially as native species are fished out and replaced with non-natives to keep up food production. In addition to these non-native species used in aquaculture, other species hitch rides on them.
How Ship's Ballast works
However, as you can see above, it is possible that all invasive species are not created equal – that is, maybe not all invasives are so bad. Green fleece, known as Codium fragile, has been introduced to the east coast of America for decades. Originating from Japan, it has typically viewed as bad – it is a buoyant species which needs hard substrates to attach, including living shellfish. It got the nickname “oyster thief” since it would attach to oyster shells, and whenever a storm or strong current event occurred, the buoyant macroalgae would be swept away, dislodging oysters and taking them away from reefs and culture sites. It is clear why this is considered a problematic species.
And yet, some recent research has shown that maybe Codium isn’t all that bad. Research which I have participated in has demonstrated that Codium may act as a viable alternative habitat for native bay scallops. Why? Bay scallops have evolved a strong association with seagrasses, and the Codium canopy likely provides the same upright structure to scallops. We observe scallops frequently in association with Codium in Long Island bays, and a study conducted showed that survival of free-released and tethered scallops was the same in eelgrass and Codium, suggesting that the invader offers a similar predation refuge. This was published last year in Marine Biology (See Carroll et al, 2010, below).
From Carroll et al 2010
In addition, I have taken the research further. The aforementioned paper talked about survival on a relatively short time span – 1 week. In order to examine the longer term effects on growth I conducted a caged field experiment the past two summers at 2 field sites with eelgrass, Codium, and unvegetated sediments in close proximity to each other. The general findings have been that scallops in Codium grow at rates similar to scallops in eelgrass, however, there are site-specific differences. There are also no differences in mortality between the habitats – suggesting that dense stands of Codium aren’t having as detrimental impact of low dissolved oxygen as I originally thought. This work isn’t published yet, as I am working on a method to find the stoichiometry of the tissues, but some of the results are in the presentation I gave at CERF 2009 here: Thursday_SCI-045_1115_J.Carroll
Moon snail crawling over Codium
However, I am not the only one who sees “positive” impacts of Codium. In the most recent issue of Marine Ecology Progress Series, a team of Canadian researchers, led by Annick Drouin, higher abundance and diversity of the faunal community in eelgrass meadows invaded by Codium fragile. Using a variety of sampling methods and field manipulations, the team demonstrated higher abundance and diversity of invertebrate organisms on Codium, and in eelgrass meadows invaded by Codium, than those without Codium. The pattern of fish abundance and diversity was not different – likely because they are highly mobile and can move easily between structured habitats. It is likely that Codium just generates MORE habitat, as it is branching and canopy forming. The important thing here is the ecological implication – the lack of a negative effect on native species by the presence of this “invader.” Perhaps Codium might not be so bad after all, especially as eelgrass is declining in many regions.
Figure from Drouin et al 2011
It is possible, then that “invasive” vegetation species in the marine environment may not always be bad. In many cases, invasives may be beneficial. Numerous studies (including the ones above with Codium) have demonstrated a positive effect of invasive algal species on native fauna. Typically, the vegetation is habitat forming, and invades areas where native habitat forming vegetation has already been lost. In essence, it is replacing a lost habitat, and creating a new habitat which is functionally similar to the species which declined/disappeared. That being said, invasive algal species can be detrimental to native macrophytes through competition. However, the benefit is in enhancing native fauna, which has potential fisheries ramifications. This requires further investigation, but it is entirely possible that non-native macroalgal species might have a positive effect on a number of native fauna.
Mud crab in Codium canopy
Pipefish chillin' in Codium canopy
The above photos, and the one of the moon snail farther up the page, are all illustrations of native species of Long Island associating with the invasive Codium fragile. Now, again, there are certainly detrimental effects of invasive species, so I am not trying to be too much of an apologist for them here. However, in the absence of eelgrass, it is entirely likely that the upright, canopy forming structure of Codium creates a habitat suitable to many seagrass associated fauna. As eelgrass is declining, invasive macrophytes might be important replacement habitats for a variety of native species. Understanding how these species affect native species will be key for management of estuaries moving forward. Particularly, once established, invasives becoming increasingly expensive and difficult to remove. If some invaders might be of benefit, that relationship needs to be well understood. Hey, invasives could help bring back the bay scallop in NY (and likely is having an impact), providing a habitat as eelgrass has disappeared from many Long Island areas. Who knows where else they might be beneficial.
There will be those of you out there who disagree. I don’t blame you. Calling an “invader” beneficial certainly goes against conventional wisdom. When we first introduced the idea of Codium as a potential scallop habitat to a shellfish crowd, we were scoffed at. However, the data don’t lie. And more research points to cases where invasives may actually facilitate natives.
Drouin, A., McKindsey, C., & Johnson, L. (2011). Higher abundance and diversity in faunal assemblages with the invasion of Codium fragile ssp. fragile in eelgrass meadows Marine Ecology Progress Series, 424, 105-117 DOI: 10.3354/meps08961 Carroll, J., Peterson, B., Bonal, D., Weinstock, A., Smith, C., & Tettelbach, S. (2009). Comparative survival of bay scallops in eelgrass and the introduced alga, Codium fragile, in a New York estuary Marine Biology, 157 (2), 249-259 DOI: 10.1007/s00227-009-1312-0
Recently, a few articles started appearing about the dramatic loss of oysters throughout the world, and how in many areas, they are “functionally extinct.” The article from ScienceBlogs talks about the findings of an international research team lead by Dr. Mark Luckenbach of the Virginia Institute of Marine Science. In over 70% of the 144 estuaries studied, current oyster levels are at 10% or less of historic levels. They estimate that over 85% of the world’s oyster reefs have been lost. The amount of loss exceeds any other shallow water benthic marine habitat that has been similarly studied. Obviously, this can cause problems.
The Underwater Times article mentions the term “functionally extinct” when referring to current oyster populations – that in some areas, oyster populations are less than 1% of historic levels, mainly due to overharvesting, disease, and invasive species introductions. But what does “functionally extinct” mean? In this sense of the term, it is when a species experienced such a reduced population that said species no longer plays a role in the functioning of an ecosystem. Obviously, the loss of any players in an ecosystem can be devastating. But oysters are a foundation species, providing a variety of ecosystem functions that renders them more important to their estuarine ecosystems than many of the other species. Oysters create biogenic 3-D structure in the forms of reefs, which build up from the seafloor and in many locations emerge from the water, particularly at low tide. This structure provides a plethora of microhabitats and niches for a variety of species to live. In addition, since oysters are filter feeders, they play an important role in nutrient cycling in estuaries, packaging things in the water column (plankton, particulates) and delivering them to the bottom where they are consumed and utilized. During this process, oysters actively clear the water column, increasing light penetration to the bottom and potentially allowing valuable submerged macrophytes to grow, adding structure to the reef and surrounding area, creating even more habitat. A number of species depend on this habitat for food ad shelter, as they are valued nursery and feeding grounds for numerous estuarine species. This function is vital to fisheries, as many finfish spend a portion of their lives foraging around oyster reefs. So when the articles suggest that oysters are becoming functionally extinct, it has serious repercussions for the ecosystem as a whole.
Clearly, the loss of oyster reefs are problems both economically and ecologically. However, some research suggests all is not lost. Stricter harvesting laws, fewer baymen, and no-take sanctuaries have helped maintain oyster populations, albeit low populations, in some areas. Better and more successful management is the first step towards saving oysters, and the report made the following suggestions for restoring and maintaining oyster reefs:
The prohibition of harvests where oyster populations constitute less than 10% of their prior abundances, unless it can be shown that dredging and other harvest methods do not substantially limit reef recovery.
New thinking and approaches to ensure that oyster reefs are managed not only for fisheries production but also as fundamental ecological components of bays and coasts that provide invaluable ecosystem services.
Steps to ensure that harvests, particularly those carried out by dredging, do not damage the remaining reefs.
Regular monitoring of reef conditions.
There is plenty of other relevant information out there about oyster reefs, research, and the issues facing them. I particularly recommend the blog In the Grass On the Reef, which focuses on research underway by Florida State researchers on salt marshes and oyster reefs. In particular, they update posts about their research in ways which are easy to understand with great visual aids including photos and videos. Definitely check that one out.
So I frequent the UnderwaterTimes almost daily. I like to find out what’s going on in underwater related news. So imagine my excitement at this article today:
The premise of the article states that scientists in New Zealand are using artificial seagrass to help boost fish stocks. Seagrass is an extremely vulnerable marine habitat, with worldwide losses. In some places where lush underwater meadows used to exist, the grass has been replaced by barren sediments. This can have an impact on fish stocks, as many marine species utilize seagrass as a habitat for at least some portion of their life cycle. So it comes as no surprise that scientists want to try to replenish fish stocks by enhancing seagrass. This is apparently what they are trying to do in a bay in New Zealand. Although, I imagine that the researchers are actually using ASUs to test affects of fragmentation on local fisheries species and not to actually be used to enhance species, it is interesting none-the-less.
I have a certain affinity for all things fake seagrass. Why? Well, a portion of my dissertation research involves using artificial seagrass units (ASUs) to investigate the impacts of patch size and shape (perimeter, area, and P:A ratios) has on scallop recruitment, survival and growth. As I mentioned already, seagrasses are important habitats, and bay scallops have long been known to associate with seagrass. Scallop populations are currently undergoing varying degrees of restoration (depending on location) but with restoration comes certain issues – namely, how are these little guys going to be affected by declining seagrass. In many areas where scallop populations crashed, seagrasses have also diminished in extent. Since seagrass is important for scallops, a decline in seagrass cover can have implications for scallops and their restoration. For my work, I use 2 sizes of seagrass mats, 8.5 and 17 square meters, and 2 shapes – a circle and 4 pointed star to maximize perimeter. Just in case those numbers don’t mean much to you, the small circles are just over 3 meters in diameter, the large circles around 5 meters across. The large star is 7 meters from tip to tip. These ASUs have 500 shoots per meter, consisting of 4 blades of polypropelene ribbon. It was quite the undertaking, and required many beer and pizza nights for fellow grad students, as well as help from local schools and scout troops.
I have generated some interesting, and unexpected, data. There is a wealth of literature out there about the impacts of fragmented seagrass habitats, patch configuration, edge effects, etc, that has been accumulating over the last 15 or so years. Going into the experiments, I had a pretty good idea about what I would expect to see – more scallop recruits along the edges of the mats, but higher predation at the edge. Growth to be slowest in the centers of the mats, etc. However, not everything happens the way I planned or anticipated. In particular, I have been working up some of my recruitment data, and I did not see a “settlement shadow” or edge effects due to predation. What is a “settlement shadow?” Essentially, bivalve larvae can be assumed to be passive particles, moving at the mercy of the currents. As a current comes into a seagrass meadow, the flow is attenuated. Particles settle out along the edge, and become diminished with distance into the meadow. Hence, recruitment is expected to be highest along the edges of seagrass meadows (and, also, the edges of my ASUs). On the opposite end of the spectrum, survival is expected to be the lowest along the edge, since predators are likely to have more access along the edges, and thus predator encounter with scallops should be higher. However, this isn’t what I saw. The reason? The dominant predator in my particular system is a small mud crab – not likely to be impeded by seagrass structure and essentially ubiquitous throughout the ASUs. This tells me the dominant process structuring post set scallop communities on my grass mats is predation, and the predator is apparently not impacted by fragmentation. This could have implications for restoration. I haven’t finished all the analysis yet, but it was pretty interesting. I just presented some of this work at a graduate symposium last week, and plan on presenting it again at the National Shellfish Association annual meeting in March.
Apparently, bay scallops made the news last week in our local Long Island newspaper, Newsday (which, by the way, has decided that you need to pay for a subscription to read their news online). And so people have asked me about it, “Whats going on with the scallops” they say, seeing as how I am Johnny Scallops and a lot of local people know that I work with them. Now, I am by no means the local expert. That distinction belongs to Steve Tettelbach of LIU, but I work very closely with him.
Anyway, onto the subject at hand. Newsday ran an article earlier this week about “scallop researchers” asking for money from the county to examine whelk predation. I don’t know the whole story, because I am not in the group that is seeking the money. That being said, if you read the article, it seems to give a negative connotation to the researchers and the fact that they are seeking money. The problem, apparently, is that some silly researchers are asking for money at all, especially on such a ‘trivial’ matter as whelks preying on scallops. According to some annoyed people, we already know that happens. (And yes, we already know a lot of things happen before we do the science, but believe it or not Joe Public, sometimes we want to know why and how it happens as well). True, whelks do eat scallops. No one will argue that. Whelks will consume lots of shellfish. I have observed them preying on scallops, clams, and slipper shells in the field. But, we don’t have answers to all the questions.
What we do know is that the county has already invested $2.7 million dollars over 6 years to the scallop restoration effort, which has produced over 6 million scallops. Each year for the past 4 years, the total landings has increased. A very, very strong argument can be made that the restoration effort is working. However, the Peconic Bays are a vastly different estuary now than 25 years ago, the last time scallops were a booming fishery. Despite our efforts, the current landings are still only ~10-15% of peak harvests. Habitat has been severely depleted and degraded. Eelgrass was once abundant throughout the bays, and is now, unfortunately, only found east of Shelter Island. This preferred scallop habitat prevented massive predation mortality by offering scallops a predation refuge. It likely prevented whelks from being able to find scallops by both providing structure and likely creating a turbulent flow that mixed the chemical cues in the water, diluting the scallop signal to the large snail predators.
But thats not the only way the time has a’ changed. Long Island waters are heavily fished. But fishing for whelk, or “conching,” is a relatively new to LI. We have no idea what the populations were like in the 1980s, because nobody cared. A quick bit of research on these animals reveals that we know relatively little about the biology and ecology of whelks in our local waters. It is entirely likely that whelk populations have increased in the Peconics with booming food sources (such as Crepidula fornicata, the slipper shell, whose populations exploded post the brown tides of the 80s and early 90s). It is also probable that whelk predators have declined due to harvesting. What eats whelks? I can’t be 100% sure, but I imagine any fish that eats things that live on the bottom is entirely capable of consuming juvenile whelks (I am thinking mainly of sea robins and toadfish for very small whelks, tautog, stripers, dogfish for larger ones), and most of the fish species around Long Island have been exploited. The real issue is we have no idea. That’s what politicians and baymen don’t seem to understand.
Take this quote from the article: “Some county lawmakers questioned the need for the new research. “We’ve had scallops for years and scungilli for years,” said presiding officer William Lindsay (D-Holbrook). “Are we just finding out that they eat one another?”
Yes, Mr Lindsay, both scallops and whelks have coexisted in Long Island waters, and waters along the east coast, for some time. However, in the past, the scallop populations were orders of magnitude bigger. We have no idea what the whelk populations were like. But when you have millions upon millions of scallops, they can swamp out most predators. Predation becomes a problem when populations are low and threatened. Small populations might not be able to sustain themselves. This is why for over 10 years post brown tides scallops didn’t recover on their own. They needed intervention. The restoration effort has produced significant increases in the scallop populations. However, it is entirely possible that those increases would be even greater, and harvest would be larger, and more dollars would be generated for the county, if whelks weren’t consuming a significant portion of the scallop population.
And that is simply what we don’t know. The researchers aren’t looking for some free handouts. But as a scallop researcher on Long Island, I can attest we are all deeply rooted to the restoration effort. We want this to work. I wasn’t around for the glory days, but I have heard enough to know about them. This research would answer some of the unanswered questions, provide for a more efficient and effective restoration plan, and ultimately increase harvest, which is the only real goal we all have in the first place. We want the scallops to come back. We want local baymen to thrive.
It is silly that people are up in arms about a $70,000 dollar budget request to examine migration rates of whelks, their abilities to home in and concentrate on freshly planted scallop grounds, and their consumption rate of scallops. These are questions, that once answered, will go along way toward restoring the glory of the Peconic Bay Scallop. Millions have already been invested in this effort and its working. Is it really so out of the question that a simple request of a mere 2% of whats already been spent be given to researchers to enhance the restoration?
True, I might be biased, because I am a research scientist. And I am very close with Steve Tettelbach, who is among the group that requested the funds. But I can attest that the goal is not to suck money from the county. Steve, and I, and everyone else involved with scallops, want them to come back, full bore, to the point where human intervention is no longer necessary. This money will help.
Is Open!!!!! Went out diving with lab mate Brad Furman this morning for some scallops. Found a good spot where nobody was fishing, heavy macroalgae (Codium fragile). Dove for 52 minutes, collected about 250 scallops myself, Brad grabbed another 125. Pretty good morning. Here’s hoping for a great
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:
Although there are a lot of them associating with eelgrass beds in Shinnecock Bay, NY. Nope, I am hunting for baby scallops. Shinnecock Bay has some of the healthiest eelgrass meadows in Long Island, and in some places within the bay, new meadows are forming. This is great, as many species depend on seagrasses as predation refuges and nursery grounds, including my model organism, bay scallops. Why then are there apparently no scallops in Shinnecock Bay? Well, its not exactly that there aren’t any, of course, but that there are so few, they might essentially be ecologically extinct. However, restoration efforts in the Peconics and larval monitoring have turned up some pretty exciting results. And, Shinnecock Bay is connected to the Peconics through a canal, whose gates are left open when there is a high tide in the Peconics, allowing water to flow into Shinnecock Bay. This is a potential source of scallop larvae. While the spawner sanctuaries are quite distant from the canal, there is a growing scallop population around Robin’s Island in Great Peconic, not far from the canal. And either way, scallop larvae spend up to 2 weeks in the water column, so it is possible for fairly long distance dispersal. So I thought we might see some scallops in Shinnecock Bay. I certainly saw some juveniles last summer, but didn’t see any adults, so their survival is likely very low. One reason is probably predation. The same eelgrass meadows that are valuable for scallops is also a valuable habitat for blue crabs and mud crabs, both of which eat scallops like popcorn (or at least I imagine that’s how they eat them). And yet, no one has investigate either scallop or blue crab recruitment in Shinnecock Bay, so that’s what I am currently doing. My scallop monitoring has already started, and surprisingly (or maybe not surprisingly), I didn’t get the results I was anticipating. Instead of the highest numbers of scallops at the site closest to the canal and diminishing numbers with distance, I had two relatively high spat numbers sites, on either side of the Shinnecock Inlet, opening up to the ocean. Could this mean a possible oceanic transport of scallop larvae into Shinnecock Bay? Is this supply-side ecology? There are clearly not large numbers of larvae, but there is a supply, and it’s coming from somewhere, but to be honest, I have no idea where. Soon I plan on sampling for blue crabs, whose larval origin I know is oceanic. If they display a similar settlement pattern, perhaps my question will be answered.
On a side note, we did collect a lot of other organisms. All together, over 20 different species of organisms came up on the collectors. The most abundant were scallops, mud crabs, blue mussels, jingle shells and slipper shells. But we also saw 2 types of sea squirts, bryozoans, rock crabs, 4 different species of snails, sea stars, urchins, other bivalves (arcs, angel wings and cockles), scaled worms and other polychaetes. Oh yeah, and a few of these things that I have as yet been unable to identify, although my guess is some sort of nudibranch. So yeah, exciting stuff indeed.
(scaled worm)
For years, the “supply-side” ecology has been a common theme describing mechanisms for benthic species distributions and densities. In general terms, the amount and extent of a particular organism is driven by the supply of larvae to a given area. This larval supply can thus be seen as driving benthic community structure, especially for marine invertebrates – as their life cycles contain a planktonic larval stage which allows for dispersal over relatively long distances. Thus, many of these populations are considered “open” and their continuation is dependent on some large supply of larvae. This makes sense, and it has been demonstrated many times in the literature. However, this has often been demonstrated on hard bottom communities. Soft bottom benthos don’t always display similar patterns. A recent paper by Dr. Megan Dethier from the Friday Harbor Laboratory at the University of Washington, details an experiment conducted investigated very small, post set, infaunal recruits. Sampling these habitats is often difficult due to the 3-D nature of soft sediments. She was able to demonstrate that for a number of taxa she was working with, the strongest recruitment was not in areas where the largest adult populations existed. This suggests that for many of the soft bottom benthos she studied, the supply of larvae is not limiting the adult populations, but rather some post-settlement processes, such as predation, competition or abiotic stressors.
LEWIN, R. (1986). Supply-Side Ecology: Existing models of population structure and dynamics of ecological communities have tended to ignore the effect of the influx of new members into the communities Science, 234 (4772), 25-27 DOI: 10.1126/science.234.4772.25
Dethier, M. (2010). Variation in recruitment does not drive the cline in diversity along an estuarine gradient Marine Ecology Progress Series, 410, 43-54 DOI: 10.3354/meps08636
This is a particularly interesting article, because “supply-side” ecology doesn’t always hold true in soft bottom benthos. I have observed this first hand with the scallop restoration work on Long Island. Over 6 years, we have monitored larval supply of scallop spat at a number of different locations, and then each winter and spring, we conduct benthic surveys for juvenile densities. There isn’t always a match between sites where we had the highest numbers of post-set and the highest juvenile densities. The main causes for this mismatch is likely to be predation or physical factors.
On another project, I am investigating scallop settlement on artificial seagrass units. I design collectors to mimic seagrass, each collector has 10 artificial seagrass shoots. Half of the collector (5 shoots) is enclosed in a mesh bag (just under 1mm) and the other half exposed to predation. There is an order of magnitude difference between the number of available settlers (those inside the bags) when compared to those actual “recruits” (those scallops outside the bags). This low pattern of surviving recruits holds up regardless of location within the grass mats (either on small or large mats, at the center or the edge). This indicates to me that predation is a major contributing factor structuring the scallop populations, at least in the estuary in which I work, Hallock Bay, Long Island.
I am a marine biologist that is currently attending graduate school at the School of Marine and Atmospheric Sciences, Marine Sciences Research Center, of Stony Brook University, New York. I am very interested in marine ecology and have been focusing my studies on bay scallop interactions with their habitats. I plan to investigate various anthropogenic impacts on bay scallop populations for my PhD dissertation. This blog will highlight the details of my graduate research, from bay scallop-eelgrass interactions as previously mentioned, to alternative habitats for scallops, such as Codium, to trophic cascades, and more. Enjoy!
Artificial Seagrass
Is a useful experimental tool to mimic natural seagrass while controlling many factors, such as density, canopy height, leaf number, which are usually confounding in natural eelgrass meadows.
Scallops seem to love this stuff!
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