Aquarium scientists run investigations here on Central Wharf and travel around the world studying marine habitats and helping find solutions to some of our oceans' most challenging problems. Thanks to the recently renovated John H. Prescott Marine Laboratory, Aquarium researchers are engaging in a series of important studies that they will be posting about here on the Global Explorers Blog. 

This post comes from intern Lauren Giglio of the Marine Fish Stress and Health Program and features work on discard mortality in Gulf of Maine Atlantic cod.

As we discussed in our first post, there is no fish more essential to New England’s history, culture, economy and marine ecosystem than the Atlantic cod (Gadus morhua). After centuries of fishing, however, the once vast cod population in Gulf of Maine is currently struggling to recover from historic lows. Today when you fish for cod, you must abide by strict quotas and size limits that have been put in place in order to help protect and rebuild the population of this iconic species. We at the New England Aquarium are part of a team aiming to determine what happens to the cod that get thrown back in accordance with these regulations.

“It’s a big one!” Recreational fishing is a popular pastime in New England waters and Atlantic cod are one of the main targets.

Together, under the direction of NEAq’s Dr. John Mandelman, we have been using two different tagging methods — one more conventional, the other more technologically modern — to track cod that are captured and released by recreational fishermen. We simulate the exact capture conditions (such as fishing gear and tackle most commonly utilized in this fishery in the region) that a cod would experience if it were hooked and reeled in by recreational fishers; however, before releasing the fish back into the ocean, we attach one of two different tags.

The first is called a T-bar tag. These small, individually numbered tags are all marked with “RESEARCH” as well as our phone number. The tags let fishing enthusiasts, like you and other fishermen, know that these cod are part of a study. Interested in helping? The next time you go out fishing and come across these specially marked fish, give us a ring! Don’t forget to let us know the fish’s identity (tag number), size (total length) and location (optimally geographic coordinates) of where you caught it. This “mark and recapture” method is simple, fast and inexpensive, which allows us to tag hundreds and hundreds of fish. However, it is also inefficient; the ocean is a big place, so the chances of someone catching one of our tagged fish are a bit slim. However, when this does happen and helpful fishers like you make the effort to contact us, the information can play an important role in determining the survival rate in these fish.

Cod were tagged with two T-bar tags, just in case one fell off.

Our second tracking method is much more complex, but allows us to more closely monitor the location of individual fish, hopefully for several weeks (in our case) after release. To do this, we attach a small acoustic transmitter to the fish. About the size of a AAA battery, the transmitter sends out a signal that gets picked up by receivers which we have placed strategically in the ocean, creating a coverage area known as an “acoustic receiver array.” Whenever one of our tagged fish swims within a third of a mile in any direction of a receiver, the receiver records the detection based on tag number. One advantage of the particular type of tag we use is its additional capacity to log pressure level at the point of the detection, from which we can approximate depth. Evidence of a tagged fish’s movement between receivers and depth are two of the primary criteria we use to estimate whether that fish is still alive in the aftermath of release, the main goal of the study.

Acoustic tags were attached to the fish between the first and second dorsal fin. These tags transmit an acoustic signal that is detected by receivers (such as the one shown on the right). Before putting these expensive transmitters on fish in the field, we did a preliminary laboratory study to make sure that the tags affixed in this manner did not detach, compromise health or impede swimming ability.

Using an array of 31 receivers, located on the southern portion of Jeffreys Ledge in waters just northeast of Cape Ann/Rockport, we were able to track the movements of tagged cod within a 13.5 square mile area.

This map depicts the location of our acoustic receivers off the coast of Cape Ann, Massachusetts, on the southern portion of Jeffreys Ledge. For our study, we deployed 17 additional receivers (indicated by black dots) to an existing array (indicated by pink plus symbols), which had been used by researchers at the Mass Division of Marine Fisheries (MADMF) for many past and ongoing projects. Our study greatly benefitted from their expertise. (Map courtesy of MADMF)

A diagram depicting the mooring system for each of our acoustic receivers. A steel weight anchors the receiver in place while a floating buoy attached to the receiver’s opposite end keeps it suspended in the water column. Each receiver is also tethered to radar reflective highflier that enables us to locate its position. When a tagged cod swims in the vicinity of one of our receivers, the receiver records the tag number. We later download this information from each receiver and use it to piece together the movement of our fish and estimate their survival rate. (Illustration by Lauren Giglio)

In mounting our study, we gave careful consideration to the fishing techniques used. The primary goal was to reflect the gear and practices used in the recreational hook-and-line fishery as closely as possible. In order to do this, we used information from a pre-study questionnaire given to fishers on their chosen practice, including bait, gear and techniques used when fishing for cod. Based on the survey results, we employed the most common fishing practices to catch cod for our study. Without considering this, the results of our study would be less applicable.

Fishing was done aboard the research vessel Alosa, captained by Bill Hoffman of MADMF, as well as the recreational fishing vessel Too Far, owned and operated by Captain Marc Stettner. Marc’s insight and expertise into New England’s recreational fishing industry and cod fishing in particular was invaluable. (Photos by C. Capizzano)

Once we had perfected our tagging methods and done our homework on the most common fishing practices, we were ready to take our study into the field. Throughout the summer, we fished within the confines of the acoustic array, as it was important to maximize the likelihood that tagged cod were detectable by our receivers for as long as possible. For each (sublegal) cod captured, we performed a series of quick evaluations and measurements. This included, but was not limited to, an assessment of the health and vitality of the fish, length measurements and noting where the fish was hooked. Once this rapid assessment was complete, a T-bar tag or an acoustic tag was attached and the animal released. We also kept careful track of the amount of time it took to reel the fish in as well as how much time it spent on deck, both of which can range depending on experience level of the fisher, whether pictures of the catch are taken prior to release, etc. This important field work was led by Connor Capizzano, a current graduate student in the Marine Science Department of the University of New England, who has been a crucial part of this project since its conception.

“Thanks for the check up, guys!  I’m measured, tagged, and ready to be released back into the ocean.  See you soon!”  Connor Capizzano, graduate student, prepares to release a cod tagged with an acoustic transmitter.

Our ultimate aim is to correlate various factors of the fish’s capture (such as what gear configuration was used, how long the fish was on the hook and how much time it spent on deck, etc.) with its health and survival. This will help us determine which aspects of capture are the most stressful for a fish and reduce survival. In turn, this will allow us to advise recreational fishers on the capture and handling methods that offer the highest likelihood for survival of these released (sublegal) cod. In this way, the findings of this study may impact how you fish for cod in the future. You may see a “best handling and practice guide” being passed out on your next fishing trip to show you exactly how to keep your future prize-winning cod safe after you release these younger individuals back into the sea.

Until next time, fish enthusiasts!
- Lauren Giglio and the Aquarium's Mandelman Research Team

Keep checking in for a celebrity guest post from graduate student Connor Capizzano and to find out what we accomplished this summer!  

Aquarium scientists run investigations here on Central Wharf and travel around the world studying marine habitats and helping find solutions to some of our oceans' most challenging problems. Thanks to the recently renovated John H. Prescott Marine Laboratory, Aquarium researchers are engaging in a series of important studies that they will be posting about here on the Global Explorers Blog. This post comes from Lauren Giglio and features work on discard mortality in Gulf of Maine Atlantic cod.

Here in the John H. Prescott Marine Laboratory at the New England Aquarium, we (Dr. John Mandelman and his research team) have been studying key questions that aid the management and conservation of certain vulnerable fish populations. Our chosen species of late? A New England favorite: Atlantic cod (Gadus morhua).

Atlantic cod (Gadus morhua), swim under a shipwreck laden with invertebrates in Stellwagen Bank National Marine Sanctuary | Photo: NOAA via Wikimedia Commons

Unless in relation to a yummy looking recipe on your favorite restaurant menu, this fish may have not crossed your mind much; however, New Englanders have a lot to be thankful for when it comes to cod. For hundreds and perhaps thousands of years, this species has been an important dietary staple of the people native to the region now known as coastal New England. The Native Americans used bone crafted hooks and natural-fiber nets to catch this local fish. When European explorers first began venturing across the Atlantic to the “New World”, arriving exhausted after enduring painfully long journeys, they needed food…badly. When they turned to the ocean as their food source, some described the cod they observed as equal in size to them! As such, this fish, which was plentiful at the time, quickly became a hot commodity. Eventually, this led to the settlement of Europeans on a nearby cape extending from the easternmost point of Massachusetts, mapped and ultimately coined “Cape Cod” by John Smith (Kennedy, 2009).  Indeed, we in New England owe this iconic species its due. Unfortunately, however, the cod populations have not fared very well in recent years, and the once vast fishery has collapsed.

The bold black line on this graph shows the total commercial landings (in metric tons) of Atlantic cod in the Gulf of Maine from 1892 to 2011. In striking contrast, the gray polygon in the upper left indicates the estimated landings from 1861 to 1880 based on analysis of historical data (Alexander et al. 2009). Figure from NEFSC 2013.

If any of you have a love for fishing—whether it be to cash in big at a local fishing tournament; to put a meal on the dinner table; or to just enjoy the environment of the open sea—chances are that while gathering your catch for the day, you’ve probably thrown something back that you either didn’t want, or weren’t allowed to keep, before calling it a day. These things that get thrown back after being caught (e.g. undersized fish) are collectively referred to as discards. The cod fishery has seen its share of discards over the years, including an estimated 2,289 metric tons of it in 2010 alone for recreational fisheries in the Gulf of Maine (NEFSC, 2012)! When you and your friends go out to sea for a fishing trip, you are legally obligated to follow restrictions specific to certain species. With cod caught for recreation (i.e. not in the commercial fishery), for example, you can only keep a certain number of fish per day, and they must all be of a certain size. But what happens to the cod that do not fit those restrictions? Well, they are simply released back into the ocean to go about their day.  …Or do they?

“What Happens to the Rest?” Illustration by Lauren Giglio, 2013

Unfortunately, the experience of being thrown back into the ocean after being caught isn’t necessarily bliss. Being captured and handled by a person can be quite stressful for the fish.  Some of these stressors include physical injury due to hooks, rough handling, air exposure on deck, and temperature changes as they rise to the surface of the sea. The accumulated effects of these stressors also make fish more vulnerable to predation after being thrown back into the sea.  All of these stressors negatively impact the fish’s chance of survival, sometimes resulting in death after the fish is back in ocean (known as “post-release mortality”); but how many succumb to this fate? Because of the nature of fish (“Just keep swimming, just keep swimming…” –Dory, Finding Nemo), it is quite difficult to determine the exact percentage of fish that die after being released back into the open water. At the same time, it is very important to have this estimate to help inform management decisions, future stock assessments, and best fishing practices (to help reduce the number of fish that die in the future). At the present time, the estimated number of cod that die when caught by recreational hook and line fishing is purely guess work, calling the need for a study to address this.

This is where our team, which includes collaborators from the University of New England, Massachusetts Division of Marine Fisheries, and hook fisherman Marc Stettner, step in. Our research studies the health effects and the mortality rates of sub-legally sized cod that are recreationally caught and released. By studying these effects, we gain a better understanding of the fate of these animals after they are released and how to alter fishing methods in order to reduce injury/stress for released animals. Through a variety of modern tracking techniques, we will follow the life of tagged cod in weeks and even months following capture in order to answer the question of how they behave and whether they live or die as a result of these handling/fishing methods. Results of this study will lead to two positive outcomes: first, to better estimate the post-release mortality rate of the species in this fishery, and second, to develop a “best capture and handling practices” guide to be distributed to the recreational fishing community to help promote strategies that reduce post-release mortality rates.
                               

One of the tagged cod who will be working with our team during the study. Where will it swim next?

Not a scientist or interested in recreational fishing in the near future? Not to fret! You have an equally important role in keeping this important species of fish going strong. By having a better understanding of the information on cod in this blog and by visiting the New England Aquarium, you have taken the first step in protecting a very important fish population. You are now able to explain how fishing responsibly is important to keep fish populations stable enough to allow us to keep making memories while fishing with friends out on the open water. If you are interested in further information on sustainable fishing and possible recipes for sustainable seafood.


— Lauren
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References:
- Alexander, K. E., W. J. Bolster, A. B. Cooper, J. Cournane, W. B. Leavenworth, A. A. Rosenberg, R. Gee, T. K. Law, R. Dunn, K. Magness, L. Rains, G. Smith, S. Brennan, and S. Claesson. 2009. Gulf of Maine cod in 1861: historical analysis of fishery logbooks, with ecosystem implications. Fish and Fisheries 10,4:428-449.
- Kennedy, Jennifer. 2009. Brief History of Cod Fishing. (Online). About: Marine Life. Accessed October 16, 2013.  
- Northeast Fisheries Science Center (NEFSC). 2012. 53rd Northeast Regional Stock Assessment Workshop (53rd SAW) Assessment Report. US Dept Commer, Northeast Fish Sci Cent Ref Doc. 12-05; 559 p. Available from:  National Marine Fisheries Service, 166 Water Street, Woods Hole, MA 02543-1026, or online
- Northeast Fisheries Science Center (NEFSC). 2013. 55th Northeast Regional Stock Assessment Workshop (55th SAW) Assessment Report. US Dept Commer, Northeast Fish Sci Cent Ref Doc. 13-01.  Available from:  National Marine Fisheries Service, 166 Water Street, Woods Hole, MA 02543-1026, or online

For the past several years, the New England Aquarium has participated in a joint expedition to Fiji, along with the Monterey Bay Aquarium and other conservation-minded groups and individuals. The last expedition took place in Spring 2012. 

Today's post about the joint aquarium Fiji expedition comes from the Aquarium supporter and Boston Harbor Cruises Vice President Alison Nolan. (Our partners at Boston Harbor Cruises present the New England Aquarium Whale Watch.) 

The Earth is covered with five oceans: the Antarctic, Arctic, Atlantic, Indian and Pacific. These oceans cover 141,600,000 square miles—or 72 percent of Earth's surface. In fact, from space at just the right time during our daily revolution, Earth appears to be almost completely covered by water.

The world seen from space is largely blue ocean. This image is of the Pacific Ocean. Image: NASA/Google Earth

But what divides the oceans other than boundaries identified by us? Where does one ocean stop and another start? Does what happens in the Atlantic stay in the Atlantic?

These are questions that we may have all wondered about but don’t often contemplate more deeply until a catalyst piques our interest. For me, that catalyst was my time spent in the Pacific with the New England Aquarium/ Monterey Bay Aquarium Joint Fiji Expedition.

Kiobo village children wave goodbye and bid us moce (pronounced moe’ they)—Fijian for see you again soon.  Kiobo is only a few feet above sea level.  Our climate changing actions in the States directly impact them half a planet away. Photo: Bailey

The Pacific Ocean is Fiji’s home and a welcoming host for our two-week journey. It is the world’s largest ocean by far, covering 69,375,000 square miles, or 35 percent of the earth. It is as big as the other four oceans combined and all of the Earth’s continents could fit snuggly into the Pacific Basin. My/Boston’s home, the Atlantic Ocean is the second largest, covering 41,105,000 square miles, or 21 percent of the Earth. It, however, is only slightly larger than half of the Pacific.

According to the World Register of Marine Species, there are 221,299 accepted marine species. It is further estimated that there are 700,000 – 1,000,000 species living in our oceans; most of which are yet to be discovered. As a new diver in Fiji, I must admit it felt as though all 700,000 were right in front of me at many, if not most, of our dive sites. I was struck at once that not only were the oceans vast, but they contained a quantity and diversity of life that in many ways outshines what is found here on land. From the smallest zooplankton to the largest blue whale, on some level, each of these species are dependent upon, and impacted by, each other in ways big and small—most of which we cannot even begin to measure. For every fish I saw, how many other species did it depend on and how many others depended on it? As a result, it is difficult to quantify what effect human interaction and environmental change is having on this delicate balance.

A banded sea krait (Laticauda colubrina) ambles through thick acropora. We nearly always see them at this site, and respectfully give them wide berth, even though they’re not as venomous as sea snakes.  Dive site: Anthias Corner, Gau Island, Fiji | Photo: K. Ellenbogen

Abundance abides: Thick clouds of plankton feeding fishes, gorgonian sea fans and crinoids make the most of this end of a bommie crest. Cakemomo Atoll is a new dive site for the joint aquarium team, and we surely were impressed by its richness. Photo: K. Ellenbogen

Blue green chromis (Chromis viridis) school around dense acroporid coral formations at  E6. Fiji’s Bligh Water and Vatu-I-Ra reef systems contain some of Fiji ‘s most beautiful and healthy animal assemblages. Photo: K. Ellenbogen

This also hit home for me during our island clean up visit to Vatu-I-Cake. On this incredibly beautiful and seemingly pristine uninhabited island, we found piles of plastic, Styrofoam and other beach debris. So, although we have drawn lines across and assigned names to the world’s oceans, this was clear evidence that both ocean surface and deep-water currents are connecting us all to each other.

Ocean surface current illustration – NOAA

Just this summer, at Long Wharf, Boston, we were excited to find a message in a bottle that had traveled from New York over a period of two months. If that bottle weren’t fished out at Long Wharf where would and could it have gone in five years? Probably not Vatu-I-Cake but maybe Brazil or Morocco…

Message in bottle | Photo: A. Nolan

Ocean stewardship and conservation should start at home.  Each of us has to do what we choose is right for us as individuals, then it should continue on to our local communities, states, country and the global community.

For me, there were already many aspects of conservation that I understood, discussed and implemented in my personal and professional life.  But, being in Fiji and seeing firsthand the vast and diverse marine populations that live just out of sight below the ocean’s surface was something unique and eye opening.
From beginning to learn the names of fish species from Bailey, Mark and Heidi, to taking in Doc Webster’s daily post-breakfast talks that opened up a new world of invertebrate zoology, to checking out Jane’s first-ever underwater pictures, I developed an emotional connection to the marine environment that was distinctly different than before my first descent. For me, that is what I will take away from the Joint Fiji Expedition, as well as new friendships, great stories, some wonderful pictures and a beautiful kava bowl.

Since returning I have also begun to dive deeper into the New England Aquarium’s programs and offerings. I encourage you too to take a look, see what piques your interest and give an upcoming lecture a try. They are great ways to see what each of us can do to both better understand and protect our blue planet. Maybe I will see you there.

— Alison