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.
Well, now I’ve seen everything. Well maybe not everything, but in all my NY diving, I had never seen this: eelgrass on an exposed, essentially oceanic sandy, rocky bottom, and a school of YOY cod. I have heard about eelgrass in these locations. I have heard that there have been increasing cod landings in NY over the past 2 winters. I have even read that juvenile cod utilize eelgrass. But I had never actually seen it until last week, when we dove along the south-western corner of Fisher’s Island.
We were out there for the day looking at some eelgrass for some new projects we are working on in the lab and in addition to collect samples for genetic analysis for a colleague’s (Jamie Brisbin‘s) research. After we were done at our site for the day, we decided to take a quick drop in along the exposed southern shore where the grass was supposed to be extremely tall and growing in a relatively rocky habitat. It was a pretty cool site – I saw typically rocky subtidal macroalgae – kelps, fucoids, coralline – with patchy eelgrass mixed in. It was pretty exciting and cool to see (although my picture below hardly does it justice).
But while I was down there, I was surrounded by what appeared to me to be young of the year (or at the most young juvenile) cod. I am in no means a fish biologist, so I might be off a bit in estimating their age, but they were definitely gadiforms, and I am fairly confident they were Atlantic cod, Gadus morhua. The distinguishing feature for me was the 3 dorsal fins. Either way, I was surprised to be surrounded by this school, although again, these pictures do them no justice. I found it difficult to get good photos – it was late in the day, the water was surgey (I just made up a word I think), and I just couldn’t get very close, so I was limited by the capabilities of my Sea and Sea camera. That didn’t stop me from trying, mind you. I was swimming, hands extended in front of me and (don’t try this at home) holding my breath while diving and snapping away. Everytime I let out a breath, they would swim away. This is poor diving practice, and I wasn’t holding my breath for long – just slightly longer than my normal breathing rhythms – it was just my best chance at getting any shots at all.
But then I realized, wow, these are a bunch of young cod and they are staying in this area where there is eelgrass. And I remembered an article I read about YOY cod and survival in eelgrass meadows. And since my experiences with eelgrass have always been in lagoonal-type estuaries where we don’t see cod (although we do see their cousins Atlantic tomcod and hake), I was excited to see both eelgrass and cod in the same place (mind you, I had never seen cod while diving either). So I was sitting on the bottom, trying to follow this school of fish and get any good pictures, and thought this is what that paper was talking about. I will detail the paper below.
The basic idea behind the paper by Ann Marie Gorman et al in 2009 was this idea of habitat patch size and edge effects on juvenile cod. I was particularly interested in this paper because the impacts of eelgrass patch morphometrics is something I have spent considerable time working on in regards to bay scallops – my research organism. So any manuscript pertaining to seagrass patch effects I try to read. This paper was pertaining to Atlantic cod, predatory mortality, and edge effects, all things of significance to my research. Since young of the year cod utilize coastal eelgrass habitats as nurseries and predation refuges, varying sizes of patches can have considerable impacts on juvenile survival. The group investigated different size patches, as well as within patch location (along the patch edge, 5 and 10 meters into the patch and into the unvegetated sediment outside the patch), and how those two factors affected the survival of tethered age-0 cod. Obviously, there are all sorts of potential artifacts with tethering mobile individuals in survival studies, however, because they are mobile, there is no other way to look at predatory mortality as specific locations within a given habitat. They observed a relationship which demonstrated lowest survival at intermediate patch sizes and highest survival at the largest patch sizes. And interestingly, they had lowest survival of tethered scallops along the eelgrass patch edge than either within the patch or in the barren habitat – and this survival increased with distance from the edge in both directions. This has been observed in other seagrass habitats, so I bought this. It solidifies the hypothesis that predators in seagrass habitats patrol along the edge of the seagrass, where prey densities are likely to be higher than in unvegetated habitats, and more easily accessible than within the seagrass patch. An interested read for those interested in spatial and landscape ecology, impacts of habitat patchiness on survival, or finifsh predation.
Gorman, A., Gregory, R., & Schneider, D. (2009). Eelgrass patch size and proximity to the patch edge affect predation risk of recently settled age 0 cod (Gadus) Journal of Experimental Marine Biology and Ecology, 371 (1), 1-9 DOI: 10.1016/j.jembe.2008.12.008
As marine scientists, sometimes we forget or don’t even realize how much local baymen and fishermen actually know. Or maybe we don’t trust them because they are “lay” persons. But they work the bay, they try to catch many of the species we study (as money is a big driver of research), and they know things. Local baymen who have worked the bay for years suggest that bay scallop recruitment is higher in years after cold/wet winters. Sometimes, we take what they say with a grain of salt. However, they know. They have often been working with these species for as long or longer than we have, and it is often also a generation thing. Generations of baymen can’t be wrong in their assessment, can they?
A 2001 study in the Dutch Wadden Sea supports these claims, however, their conclusions are not what you think. Matthius Strasser and Carmen-Pia Gunther observed patterns in larval supply of predators and prey after a series of consecutive winters in which temperatures were severe, moderate or mild. Originally, the prevailing thought was that egg production increased after severe winters of many benthos, and this is why recruitment was higher in the following spring. However, their research indicates that the numbers and peaks in recruitment were actually highest in the mild winter. So why isn’t recruitment highest during these years? Their theory, a mismatch in the predator and prey larval supply. After severe winters there is a delay in the peak larval supply of the major predators, green crabs, of almost 6-8 weeks. This delay is not as apparent as their bivalve prey, and with the average larval time of the bivalves also being shorter, they settle much earlier than the green crabs and have a potential head start in growth. According to the researchers, this mismatch is what fuels observations of higher recruitment after severe winters.
An alternative scenario is one which was observed in Chesapeake Bay. Using local climate response variables Kimmel et al were able to demonstrate noticeable and significant differences in phytoplankton, copepod, gelatinous zooplankton and finfish abundances and composition between years with “wet” winters and years with “dry” winters. Essentially, wet winters led to an increase of freshwater flow and nutrients into the system, which resulted in higher phytoplankton, more copepods, more ctenophores and higher numbers of striped bass. In years of dry winters, there was less phytoplankton, more scyphomedusae and more menhaden. The basic premise is that the local climate had a significant impact on the community composition of Chesapeake Bay by controlling the amount of fresh water flux into the system.
Both are interesting reads, and the idea of the interplay between climate and marine ecology is one that is becoming even more important to understand with the current climate change scenarios. It is quite clear that atmospheric conditions and local climate can have a fairly significant impact on subsequent year classes – something baymen have been familiar with for decades, if not centuries, but something marine scientists have only been exploring for the past decade, give or take.
Strasser, M. (2001). Larval supply of predator and prey: temporal mismatch between crabs and bivalves after a severe winter in the Wadden Sea Journal of Sea Research, 46 (1), 57-67 DOI: 10.1016/S1385-1101(01)00063-6
Kimmel, D., Miller, W., Harding, L., Houde, E., & Roman, M. (2009). Estuarine Ecosystem Response Captured Using a Synoptic Climatology Estuaries and Coasts, 32 (3), 403-409 DOI: 10.1007/s12237-009-9147-y
Apparently, climate change might not be such a bad thing. Especially not if you are an exploited species of bivalve. Now I am not trying to be a climate change apologist, but too often we get caught up in this debate and science is 99% of the time on the side saying “It’s bad.” However, as I have learned in my own research with invasive species, there are always two sides to every coin. A warming ocean could be a benefit to numerous species, probably as many species as it might be of detriment. Obviously, there are a whole suite of ecosystem processes that are also affected, but in certain cases, it might not be so bad. At least not according to a paper in Marine Biology entitled “Strengthening recruitment of exploited scallops Pecten maximus with ocean warming.” Its an interesting read. The essential idea is that over a long(ish) time period, the researchers were able to demonstrate a highly significant correlation between increasing temperature and increasing settlement and recruitment of juvenile scallops to a local scallop population. Shifts in recruitment can be attributed to temperature related shifts in feeding, gonad development and larval survival – and this impacts are more apparent in species who use environmental cues to induce development and spawning. Such is the case for many species of bivalves, including scallops, and so a warming ocean could potentially enhance scallop recruitment. There are some stats involved in their methods, but the basic results are pretty simple, over the past decade, scallop landings around the Isle of Man have been increasing. IN addition, mean springtime temperatures have been increasing (which cues development). I know what you all might be thinking, correlation does not equal causation (you know the one, mean global temperature has increased as the number of global pirates has decreased, meaning that the number of pirates somehow influences the climate), but that goes into their methods of using residuals and proxy values and all sorts of things. Basically, recruitment increase isn’t significantly related to other things (spawning stock, dissolved oxygen, chlorophyll a), and is strongly related to temperature. They even examined a number of scallops during the three month conditioning period and the GSI – which indicates relative gonad development – was significantly higher in years when temperature was higher. So when temperature goes up, the scallops develop larger gonads and subsequently release more larvae which show up as strong recruitment classes.
So what does this mean for bay scallops? Well, there are plenty of issues with ocean warming and bay scallops – and one of particular concern is predator range expansion and new predators coming into the bay scallops range. In terms of recruitment, we haven’t seen any patterns that would suggest this is the case in New York. However, there hasn’t been many scallops here to spawn over the past 20 years until recently – due to the restoration efforts – and there needs to be a local spawning population in order to observe any of the patterns described from the paper. That said, bay scallop recruitment is not likely to be effected by ocean warming in terms of larger populations – although timing of first spawn might change, the number of times they spawn might change, etc, but it is my opinion that there are numerous variables that influence the size of recruitment classes in local scallop populations, particularly in the bay, which is already a dynamic environment.
Shephard, S., Beukers-Stewart, B., Hiddink, J., Brand, A., & Kaiser, M. (2009). Strengthening recruitment of exploited scallops Pecten maximus with ocean warming Marine Biology, 157 (1), 91-97 DOI: 10.1007/s00227-009-1298-7
Wow, first, I did not realize it has been such a long time since my last update. I have been very busy with writing a manuscript and trying frantically to finish up the field season (although I still have another month to go). A few weeks ago, I went out sampling for my recruitment squares. If you remember, my last post about them suggested that I should not abandon hope, as I was finally starting to see some small spat. I was, of course, very excited. Well, I was dealt a crushing blow. Two weeks ago we were seeing a very high number of spat in collectors within Hallock Bay, which lead me to believe that I would most certainly find spat this time around on my mats, at least more than the last time, even if it wouldn’t be alot. So, extremely excited, my advisor, Dr Brad Peterson, and I headed out to my field site to collect my recruitment squares from my grass mats. Now, this is no easy feat, and requires a few hours in the water searching for them (I guess I could have planned the relocation aspect a bit better) and a couple more hours going through the samples. As always, I have my own set of spat collectors at my site which I use as a “control;” the idea here is that if there are larvae in the water, I know they will recruit to the collectors, and that will give me a decent idea of what I might expect to see. I always process the collectors before my squares, so I know what to look for (ie, should I see any scallops at all? what sizes should I be looking for?). Well, as it turns out, I had a fairly large number in my collectors, which had me thinking awesome! My recruitment experiment is finally coming together!
2 hours later, I had a decidedly different opinion on my recruitment experiment: FAILURE!!! We found only 1 scallop spat on all the squares collected. ONLY 1!!! This is not nearly what I was hoping for, and certainly doesn’t bode well for what I thought would be a fairly big portion of at least 1 chapter of my thesis work. It is pretty disheartening, putting in all that work ( a full day’s worth of work for 2 people) to only come away with 1 scallop. Granted, the supply in the system might not be very high, and I might not have received numbers good enough to run any sorts of statistical analysis. However, 1 scallop? On a day I expected to see many more, given what had happened on the last time I sampled my squares and what we saw in our spat collectors. But no, it is a failure. I have one more collection scheduled, next week, and then I can truly decide which is a bigger failure, my recruitment experiment, or the New York Mets season.
So, a few posts back I was disappointed in the lack of scallop spat on my mats and in Hallock Bay in general. We had not really seen any in our collectors which we use to monitor spat in any of the collections, and so I was not so upset that I wasn’t finding them on my mats, just figuring they weren’t around. I was a little worried though, since scallop recruitment is a part of my research, and I was already thinking about possibilities of new locations for next year. I was ready to give up on the recruitment thing all together, since it is a lot of work to make the recruitment squares, to search for the squares within the mats, and to put new squares back on, not to mention I didn’t want to keep wasting fuel for fruitless boat trips to my site. However, after much deliberation, I decided to make a new set of squares over the weekend to put one more set out there, just to be sure I wouldn’t miss it.
Well we went to the site on Monday to collect my 3rd set of recruitment squares and to replace them with the 5th (and final) set. I also keep a set of spat collectors at the center of my array to make sure scallops are recruiting to the area using a known method for sampling them. I always process the spat collectors first, just so I have an idea of what to expect on my squares. Guess what?
Scallop spat in my collectors!! This was exciting. It wasn’t a lot, only 16 total out of 3 bags, but I honestly didn’t think I would see any. I still wasn’t sure what to expect on my mats, but at least I was happy there were spat in the area. After processing all the recruitment squares, I did have spat on the mats! Success!! Well, kind of – we only found 4 total spat on the squares, not quite numbers that I can use for any kind of stats. However, now I know that if there are spat in the area, they will potentially settle on my mats, which was very refreshing to find.
Oh, and there is better news, the spat that we found was mostly small – 2-4mm. This is good, because it means the spawn happened relatively recently, and will probably show up on my next set of collectors. Second, and more exciting, is what we found today – in our spat monitoring we have 5 sites within Hallock Bay where we have sets of collectors, and we found spat at all of them, and in decent numbers (some bags over 20 scallops) and again, many were small. So I am keeping my fingers crossed that I will see much better numbers on my mats during my next collection!
Well, I realize that I started this blog and never put any updates into it… Oops… It has been a busy summer filled with long days on and in the water, but with some excitement as well… I finally put my artificial seagrass mats out in the field in July, which was a very exciting day… The idea behind the artificial mats is that the local estuarine habitats are changing from once dense meadows of eelgrass to small isolated patches… Nobody is really sure the impacts of this changing habitat, and rather than disturb the already stressed existing eelgrass, we chose to make our own artificial mats… This also allows us to make them all the same, in terms of number of shoots, blades, etc :
Once they were in the water, they looked great… The ribbons stood upright… They were quickly colonized by small fish like silversides and killifish… Soon the mats were colonized by other fish, like pipefifh, tautogs, cunner, and even some small flounder and sea bass, and many invertebrates, including grass shrimp, mud crabs, spider crabs, blue crabs and whelks… The mats also experienced epiphytic algal and bacterial growth and also received a fair amount of drift algae… All in all, it was very impressive and far exceeding my expectations:
I placed scallops out in these mats, 10 to a bag, to prevent predation, in order to measure scallop growth… They have been growing well, around 25 millimeters (around one inch) in 8 weeks time… These are about triple the size of when I put them in (averaging around 11-12 mm, and now between 35-40mm)… These are very exciting results, although I don’t have pictures right now to show… I attempted a predation experiment with tethers, however, this wasn’t very successful, as I had extremely high mortality that I could not attribute to predation…
I have also worked on spat collectors located in various locations throughout the Peconic Estuary, with some fairly exciting results… This is part of a large bay scallop restoration effort undertaken by Suffolk County and the Cornell Cooperative Extension of Suffolk County… This effort includes researches from various parts of Long Island, as well as dozens of local volunteers, to spawn scallops in captivity, grow them out in field settings and hang millions of them in lantern nets in close proximity in the hopes that having that many close together will enable them to spawn in the wild and allow larvae to recruit throughout the bays… This is the first full year with the high density of scallops in these lantern nets, although various other spawner sanctuaries have been set up for the past few years… All the data is still coming in, so nothing concrete yet, but there are some real positive signs that this type of method might be working…
Finally, I am also investigating the effectiveness of alternative habitats… I have looked at free planted and tethered scallops in alternative habitats for the past 2 summer seasons… Stay tuned for the results…