Well, since all I have been doing all week is field prep, I don’t yet have pretty (or interesting pictures) nor have I had much time to dive into the literature. But I did notice that lionfish were in the news again, as the 2011′s first Lionfish Derby in the Florida Keys happened this week. Those who follow Chronicles know that I have blogged about lionfish quite a bit. Last fall I did a post about lionfish derbies in Florida. More recently, I did a fairly popular post about invasive lionfish, and had a celebrity post by a labmate of mine who does sponge research in Jamaica and is now an avid lionfish hunter. Heck, I even posted about lionfish on my first blogsite !
So this shouldn’t come as any surprise that I am doing yet another lionfish post. By this point you know the story. They are a Pacific reef predator that has been introduced to the Atlantic. They can now be found in great numbers throughout Caribbean and Florida reefs, but can also be found as far up the east coast of the US as Long Island! There are many potential problems of having this novel reef predator on already impacted reefs in the Atlantic, so its a situation people have been monitoring for quite some time. And their ever increasing numbers have led to attempts at eradication.
2011 will be no different. The first of three Florida Keys lionfish derbies was held earlier this week. Considerable cash and other prizes were offered to teams with the highest catch, and both the largest and smallest fish. Over 500 specimens were hunted and killed. That’s the good news. The bad news? It only required 10 teams of between 2-4 people showed up to catch the 531 lionfish. Last year, the same derby had 27 teams catch 534 fish. While one could argue that this year’s teams were more skilled lionfish finders, it is also likely that this is an indication of more lionfish. A catch per unit effort type thing.
Fisheries researchers often use catch per unit effort – CPUE – because sampling effort may vary from one time to another, or from one place to another, and so CPUE standardizes the individuals caught to the effort exerted. Not knowing anything about the actual number of total participants, if we use “teams” as the effort, this year’s CPUE was 53.1, over two and a half times more than last year’s CPUE of 19.8. So what does that mean? Now I am not a fisheries biologist by any means, and so I might be giving a totally oversimplified explanation, or I might be wrong altogether (and hope someone corrects me), but while CPUE is not a direct measure of fish population abundance, it is an oft-used proxy. The increase in CPUE this year from last year likely indicates an increase in population.
CPUE is itself problematic because it is typically fisheries-dependent data. Its value as an estimate of abundance varies with the catchability of the particular fish species surveyed and the efficiency of the gear being used. A major assumption of CPUE as a proxy for abundance is that the relationship between catch and abundance is linear, ie, the more fish, the higher the CPUE (you can learn more about estimates of abundance from this UNCW lecture) This is the assumption I am making with the lionfish population in the Florida Keys based on my simple, back of the envelope calculations. Again, there are problems using fisheries CPUE since it is often not proportional to abundance – fishers become more efficient over time and don’t fish randomly. But for the sake of this argument, it is probably safe to say that lionfish populations in the Florida Keys are on the rise. Stay tuned for more after the final 2 derbies.
Check back as I am sure I will make edits when more fisheries minded people read and comment.
EDIT: A follower sent me this video of a new tool being used to capture lionfish which may be more efficient than a typical spear gun. Plus I like the soundtrack.
Edit 2: A new blog has jumped into the fray of lionfish blogging, with this post of a very good video on the subject. The blog is SeaMonster – started by Jon Bruno and Emmett Duffy. It is really good, so you should definitely check it out.
Well I finally picked up a copy of the this month’s National Geographic with the artificial reef article in it. And by picked up I mean borrowed from a waiting room, but I have to go back on Thursday and will return it then, so I am no thief. Anyway, I briefly blogged about this article already when I was depressed about winter weather and longing to be someplace else, preferably warm, and diving. That’s because I love diving. And sometimes, there’s nothing better than diving on wrecks. Sometimes. Don’t get me wrong, there is plenty of cool things to see on naturally occurring bottom. But artificial reefs created by wrecks are definitely very cool (so is this video).
Image from Pangea-yep.com
But actually reading the article, in print, and seeing the pictures, made me want to blog about it all over again. This time, though, I will concentrate a little more on artificial reefs themselves. Artificial reefs are quite simply structures artificially sunk by man to create a hard bottom in an otherwise sandy and structure-less habitat. The idea is to mimic some of the functions of naturally occurring reefs – namely, by providing a hard, 3-dimensional structure that sits in the water column. These reefs are intended to attract and enhance many marine species, in particular, finfish. In fact, fisherman have been sinking things for decades (probably even centuries) to attract fish, so this is not a particularly novel idea. However, the number and magnitude of artificial reefs has certainly expanded greatly in recent years (Edit – as Dr Alan Dove pointed out in the comments below, there have been numerous “natural” or unintentional wrecks sunk over the years. So the rate of sinking artificial reefs might not have increased, but I imagine the rate of intentionally sunk reefs has). Typically, “Artificial reefs” just consisted of junk. Now, many have expanded to be large decommissioned ships, subway cars, and oil rigs (and other cool things). And even more recently, companies are creating artificial reefs from concrete, such as Reef Balls, which I think are pretty cool (and, if you are lucky, when you die, you can be commemorated for eternity as an artificial reef ball! Sign me up!).
It might not happen over night, but eventually these sunken structures become teeming with life. Swirling currents around these structures can kick up and contain plankton, which attracts small planktivorous fish. These little guys, in turn, attract larger piscivorous fish. In addition to seeking food, many fish arrive simply to seek shelter in the many nooks and crannies that artificial reefs provide. But its not just fish. The artificial structures also become colonized by invertebrates and macroalgae, creating a crusty layer of living organisms growing as a living shell of sorts on the submerged structure. This living structure offers more nooks and crannies for smaller creatures, and provides food for numerous species that inhabit the reef. It essentially becomes just like a natural, living reef, with the only difference being that the underlying structure is man-made. Typically, when we think of artificial reefs, we think of tropical locations. However, they are also used in many temperate coastal waters to enhance fisheries, including Maryland, South Carolina and New Jersey. Here, they create ecosystem structure typically only present on the few limestone rocky outcroppings that stick out of the sand bottoms.
Despite providing food and shelter to numerous species, there are certainly detractors, and artificial reefs aren’t without certain cons. One major concern is that some things are just tossed in the ocean as junk, but that companies/organizations/municipalities/entities use the “artificial reef” moniker as an excuse to dump crap. Its cheaper to just toss things into the water than dispose on land, and so sometimes, things are called reefs just as an excuse. That is bad. Additionally, many things that are sunk have toxic substances on them, which can actually do more harm to the environment, leaking contaminants for the life of the reef. It is for these reasons that there are now strict, stringent regulations for sinking artificial reefs.
But one of the biggest complaints against artificial reefs is the very reason they are created in the first place – they concentrate fish. The complaint is that these concentrations make fish easier targets for fishermen, and can be potentially harmful to specific species. According to the NatGeo article, some biologists believe that this artificial enhancement of certain fishes, can be extremely detrimental to stocks. One such fish that is likely being negatively impacted by artificial reef structures is the red snapper, which concentrate around the structures and become easy targets for fishermen. In other words, these artificial reefs might make fishing as easy as shooting fish in a barrel. Obviously, acting as fish attractants with easy access can be harmful to fish populations, and some might argue that recreational fishermen are quite capable of decimating fish stocks, even in the absence of commercial fishing pressure
Clearly there are pros and cons of artificial reefs. However, it is my opinion that the pros outweigh the cons. And an easy way to eliminate the major negative impact of artificial reefs – the potential to overfish exploited stocks due to large congregations of target species around these structures – is to incorporate reefs into marine reserves and no-take zones. Yes, this might defeat the purpose of the reefs, and many will argue against this. I am not suggesting all artificial reefs become no take zones, but by leaving some as no take refuges, the reefs could serve there original purposes. While there is some debate as to the usefulness of marine reserves on highly mobile species, it stands to reason that artificial reefs create habitat where there is otherwise none, and enhances the local ecology of the area of the reef, enhancing species abundance and diversity. Plus, they are just awesome to dive on.
Well, more bipartisan cooperation this week, which after almost 2 full years of bickering is a bit refreshing. Especially when it comes to a fisheries related issue – shark finning. Yesterday, the bill went through the Senate, and this morning, passed through the House. Now all Big-O has to do is sign the thing into law. Although some measures of protecting sharks have been in place for some time, shark finning was popular since the fins fetch considerably more dollars than other shark meat. This practice involves catching sharks, cutting off their fins and throwing the finless fish back overboard. I guess this is in an attempt to maximize landings of valuable meat, as I assume catch quotas are on a poundage basis. Now, all sharks landed have to be kept whole. Additionally, other vessels cannot transport fins. Not knowing much about the shark fin trade, my guess is that most shark people will see this as good news. Of course, there is always exceptions, and a smooth dogfish fishery will be allowed to continue finning practices, but such is the cost of compromise in getting enough support for the bill to pass. Hopefully this is all a step in the right direction. WhySharksMatter over at Southern Fried Science blogged about it today, so check it out. Also, to learn more about shark finning, check out this post from Ya Like Dags from last month.
Pole caught tuna... Dinner and lunch for all of us at the resort...
So I was checking out Ocean Treasures today, and Alli had an interesting post about trying new foods/ foods she doesn’t necessarily like. While that might not be of interest to most of you, the interesting thing I picked out of her post was this fishery in her local Canada that operates similar to a farm share. Nova Scotia now has what might be the first CSF – community supported fishery. (Note – not the first, a quick google search turns up quite a few ) You can read more about the deets on this blog. So I looked it up. It is called Off the Hook (quite the catchy name, I think). This works just like a CSA – community supported agriculture – in that members of the community buy shares in the fishery. Off the Hook brought a group of small-scale hook and line groundfishermen’s catch to the local community of subscribers. The subscribers get weekly deliveries of fresh fish, cooking tips, and an opportunity to meet the fishermen. Direct from the website:
“Like other direct marketing enterprises, CSFs can provide several benefits to small-scale fishers, including more family income, more market choices, and increased ownership and livelihood control. Since there are no ‘middlemen’ involved, fishermen can ensure a fair price for their catch. Because subscribers sign on to share risks, CSFs can also help keep protect fishermen’s safety by allowing them to decide when it is safe to leave the wharf.
Meanwhile, Off the Hook’s subscribers enjoy increased access to the freshest local, traceable, high quality fish along with renewed connections with local fishing communities and the ocean that sustains us all. Off the Hook’s fish shares will never be old, frozen, or badly handled, and will always be caught by fishers who believe in sustainable fishing practices and are working for the future of their communities.”
Seems simple enough. It could help to maintain fisheries stocks. It is good for the environment in many ways – catching less fish, little or no by-catch, no habitat degradation, lower fuel costs, no shipping, etc. This idea help supports the idea of becoming locavores, which will lead to a more sustainable future. And, to the benefit of fishermen, because community members buy “stock” before the season, they help support fishermen when times are lean – the burden is shared by the whole community who wants fresh fish, not the few families who work hard to provide them.
When I spent some time in Fiji last winter, we stayed at an eco-adventure resort. Obviously, I was there for the diving. But it is also a popular fishing spot (with many records landed by visitors at the resort). That said, the fishing that takes place there, the fish caught are utilized by the resort for food, and also given to the local villagers (pictures are from my trip). A similar system.
It is such a good idea, I am surprised it is not embraced more widely. I guess the allure of the big pay-day might keep many fishermen uninterested in such a program. Although one would think that a steady paycheck would be more beneficial. Either way, I hope more of these things are enacted. I can certainly rally behind this type of fishery.
A recent article in the Press-Register of Mobile, AL, has highlighted some work by a group of Dauphin Island Sea Lab researchers. Now, we all know of the many negative consequences of the oil spill, and they have been highlighted on numerous blogs and websites (see some of those here and here). Now I first read about increases in baby fish in Gulf of Mexico estuaries back in September. Researchers had been monitoring juvenile fish abundances for a number of years, and when it came time to conduct those surveys this summer, after the spill, it appeared as though everything was normal. Some species even were more abundant than normal. So it seemed as though GoM fish larvae had dodged a bullet from the oil spill.
Now, just this week, the DISL crew is at it again. Trawl surveys at a series of sites have yielded significant increases in fish abundance post-spill. This doesn’t mean that the oil benefited the fish. Rather, the researchers are suggesting it was the forced closure of some of the richest Gulf fishing grounds that led to these dramatic increases, strong evidence for the dramatic impacts fishing pressure has on the marine environment. And unfortunately, this unexpected result may make it difficult to truly assess the impacts of the Deep Horizon spill for quite some time.
“There has been an awful lot of debate about longlining, gill netting, commercial fishing, recreational fishing, about how the ocean has been restructured by man,” Valentine said. “This was the first time we’ve ever seen such a large scale cessation of fishing.”
He said that the fishing closure appears to have demonstrated for the first time “how resilient the ocean really is if widespread management measures are applied.”
However, the GoM is hardly in the clear, and all the researchers involved are quick to point out that this increase isn’t necessarily good news. Many fish and fish larvae were likely lost in the spill, and it will taking longer to discern these effects with the dramatic impact the fishing closure had on the data. Either way, it is an interesting story, and certainly one worth thinking about.
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.
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
The cracked bay scallop shell indicates crab predation.
Over-fishing is a relatively hot topic these days. One group of fishes that are particularly threatened are sharks – because they are large, long lived, and have relatively few offspring. Here an excerpt from a recent article online:
“GENEVA – More than a quarter of sharks in the northeast Atlantic Ocean face extinction with some species already wiped out in certain areas due to over-fishing, a conservation group said on Monday.
Twenty-six percent of sharks, rays and chimaeras are threatened with extinction and another 20 percent are in the ‘near threatened’ category, the Switzerland-based International Union for the Conservation of Nature (IUCN) said in a statement.”
This has the potential to be devastating to bay scallops. With the loss of sharks, which are large apex predators, their prey is released from a predation pressure. This, in turn, allows populations of shark prey to expand – these include smaller sharks, skates, and rays, which are typically benthic feeders which eat shellfish. One species in particular has increased to such numbers, the cownose ray, that it has devastated the bay scallop fishery in North Carolina. This has been documented by scientists for the past 8 years, and recently made Science magazine in 2007. Luckily, we don’t have the large feeding aggregations of cownose rays here in New York, and as far as I can tell, we haven’t seen large increases in skates, at least not in areas where we have bay scallop populations.
Although it is possible that we are seeing other trophic cascade-type effects, some of which I plan to investigate in my thesis research. I don’t want to get into too many details until I know if I am doing this for sure, but its possible that loss of some local fishes has released crabs from predation pressure, allowing them to forage more freely on their prey, juvenile bay scallops included. By the way, I am working on my proposal right now and it is killing me! Can’t wait until it is all over!
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!
Recent Chronicles comments