An Ocean Warming: Atlantic Cod and Northern Shrimp Search for Colder Water

Perhaps no other New England species has felt the effects of the Gulf of Maine’s rapid warming like the fabled Gulf of Maine cod. An iconic species since its discovery centuries ago off of New England’s coast, cod profoundly impacted the way our region developed, and has shaped our coastal economies.

Today, however, the state of the species looks much different, with cod stocks in the Gulf of Maine hovering around three percent of what scientists say are sustainable levels. In an attempt to quell the overfishing of cod, restrictions on fishing quotas have been enacted. However, instead of seeing the cod stocks rebound, the numbers have continued to plummet.

There are two reasons for this: First, continued fishing pressure hasn’t allowed for enough of an opportunity for cod populations to recover. The other reason? You guessed it: drastic warming due to climate change.

Cod’s home is no longer the comfort zone

Climate change has led to warming ecosystems all over the world, but the Gulf of Maine is experiencing this warming trend faster than most. Cod, like every species, has a range of temperatures at which they can live comfortably, which in turn makes a range of geographical areas suitable for them. Historically, the Gulf of Maine has been at the southern boundary of their range. But, with Gulf temperatures rising due to climate change, cod are now starting to move north in search of cooler temperatures.

Because of this shift, restrictions on fishing quotas, even if effective on their own, have failed – as they didn’t account for what would happen due to warming waters.

As scientists and fishery managers have begun digesting this information and its implications, they are increasingly calling for something called “ecosystem-based management,” a management principle that considers the environmental factors in play in a given ecosystem. With widespread use, this broader understanding of what’s happening, and why, could provide a brighter outlook for the future of Gulf of Maine cod.

Northern shrimp headed further north

Another Gulf of Maine species, northern shrimp (pandalus borealis), face a similar situation. This small crustacean is an integral part of the Gulf of Maine food web. It’s unique because it is hermaphroditic, meaning the shrimp first mature as males at around two and a half years of age, and then about a year later develop into females. Northern shrimp feed on plankton and benthic invertebrates, and are then prey for several important species of fish, including cod, redfish, and hake.

For decades, the northern shrimp fishery thrived, until a few years ago, when stocks showed massive declines and low levels of shrimp reaching the age when they’re large enough to be fished. Particularly warm water temperatures during what is known as the “ocean heat wave” of 2012 caused stocks in the Gulf of Maine to drop even more dramatically. Although heavy fishing pressure is partly to blame for the driving the stocks down, scientists also point to the shockingly low levels of fishable shrimp. As the northern shrimp’s lifecycle is highly dependent on temperature fluctuations – with colder temperatures producing higher levels of fishable shrimp – the decline can be linked to warmer waters.

Northern shrimp, like cod, have a narrow range of temperatures in which they can thrive and, similarly, the Gulf of Maine is at the southern end of their range.

Long-term fishery closure a warning sign

Since 2013, the northern shrimp fishing seasons have been closed entirely. With ocean temperatures predicted to continue their warming trend and the species’ already vulnerable status, it looks increasingly bleak for the fishery.

Little by little, we are losing cod and shrimp to colder waters, and others soon may follow. It’s clear the Gulf of Maine and its composition is changing. That’s why plans to mitigate climate change must pay close attention to oceans and the warning signs they’re giving. And in the meantime, fishery managers must do everything within their power to ensure that management strategies incorporate the best climate science possible.

 

 

Happy New Year from New England Ocean Odyssey!

Happy New Year, New England ocean lovers! Here are some of New England Ocean Odyssey’s highlights from 2015:

We featured some special species from areas rarely seen with the human eye:

Atlantic Treasures of the Deep

We brought you news about the threats facing our ocean’s wildlife – from overfishing and poor fishery management, to climate change, to oil exploration.

Exploring for Oil Off Nova Scotia Threatens Ocean Wildlife and Our Coastal Economy

The Climate Change Connection: The Warming Gulf of Maine Needs Protected Areas

Fishery Council Vote: Major Losses Overshadow Small Victories

We featured sea creatures each week with our summer Fish Friday series.

Fish Friday Finale

And we went back for another dive at Cashes Ledge.

Beyond the data: Captivating moments at Cashes Ledge

Dive in on Cashes Ledge 2.0

In the fall, we ramped up our efforts to permanently protect Cashes Ledge and the New England Coral Canyons and Seamounts.

Save the Whales: Create marine protected areas

Governor Baker: The People Have Spoken, and They Want a Marine National Monument

We learned that climate change is exacerbating an already poor outlook for Atlantic cod in New England.

Baked Cod: The Path Forward in an Era of Climate Change

Will Atlantic Cod Exist in 2036?

In 2016, we’ll keep fighting for a healthy ocean in New England, to protect our wildlife and our coastal communities. Thank you for your support!

Will Atlantic Cod Exist in 2036?

Kelp Forest and Cod at Cashes Ledge; 70-miles off the coast of Maine
Cod today.
2036?
2036?

Imagine it’s 20 years from now, and your grandchild is about to head to bed – but first, she wants to hear a favorite bedtime story, “the one about the fish.” You pull it off the shelf – Mark Kurlansky’s The Cod’s Tale – and begin reading. Unbidden, her eyes widen at the vivid illustrations of the fish with a single chin whisker, at how it has millions of babies, and at how it gave birth to this country.

Every time you read her the story, she asks the same question: “Can we go catch a cod tomorrow?” Every time, you have to tell her there aren’t any more cod in New England. And, every time she asks: “Why?” But you never really have a good answer for her.

Farfetched? Maybe. But unfortunately, local extinction of New England’s Atlantic cod population is no longer out of the realm of possibility.

No Happy Ending in Sight for Cod
The crisis in New England’s cod fishery was once again on the agenda at the New England Fishery Management Council’s December meeting in Portland, Maine. And once again, managers failed to take the basic actions needed for a concerted effort to restore this iconic fish.

In addition to the collapse of the cod stock in the Gulf of Maine, New England is facing even greater declines of cod on Georges Bank, the historically important fishing area east of Cape Cod.

The outlook for cod keeps getting worse, and the “actions” taken by the Council are so unlikely to make a difference that we must continue our call to save cod.

The Worst of the Worst
Some recent analyses have concluded that the cod population on Georges Bank is the lowest ever recorded – roughly 1 percent of what scientists would consider a healthy population. Other estimates put the population at only about 3 to 5 percent of the healthy target. The cod stock in the Gulf of Maine is hovering for the second year in a row at roughly 3 percent of the targeted healthy population.

At its meeting last week, the Council did set new, lower catch limits for the severely depleted Georges Bank cod, but, true to form, those limits don’t go far enough. The Council is clearly in denial about the state of this fishery. If there is even a chance the number is 1 percent, this should be cause for major distress among Council members and fishermen alike.

The Council’s actions (or, really, lack of action) leave me wondering, again, whether anyscience would ever be “enough” to compel them to halt the fishing of cod entirely.

Habitat Loss Adds Fuel to the Fire
Astoundingly, the Council also decided earlier this year to strip protection for important cod habitat on Georges Bank – amounting to a loss of some 81 percent of the formerly protected cod habitat.

To recover, depleted fish populations need large areas protected from fishing and fishing gears; they need protected habitat where they can find food and shelter and reproduce; and they need large areas where female cod can grow old and reproduce prolifically. However, our fisheries managers – who are entrusted with safeguarding these precious resources for future generations as well as for current fishermen – ignore this science and continue to stubbornly deny the potential scope of this problem.

This is an especially irresponsible stance in light of climate change. Not only are New England’s cod struggling to recover from decades of overfishing and habitat degradation, now the rapid rise in the region’s sea temperatures is further stressing their productivity. Protected habitats help marine species survive ecological stresses like warming waters.

If a Cod Fish Dies But No One Records It, Did It Ever Really Exist?
As if matters couldn’t get worse, the Council also voted to cut back significantly on the numbers of observers that groundfishing boats would have to have on-board to record what fish are actually coming up in their nets. This is little more than the Council’s blessing of unreported discards of cod and flounder and other depleted fish.

We should be protecting more of these areas, not fewer; we should be doing more for these iconic fish, not less. So why is the Council making it so much harder for cod to recover? Perhaps it is simply contrary to human nature to expect the Council’s fishermen members to impose harsh measures on themselves when the benefits may only be seen by future generations. Perhaps federal fishery councils comprising active fishermen only work well with healthy fisheries.

Federal officials at NOAA Fisheries will have the final say on these Council decisions to strip habitat protections, cutback on monitoring, and continue fishing on cod. We can only hope those officials will start taking the tough but necessary actions, giving New Englanders at least a semblance of hope that our grandchildren will be able to catch a codfish, not just read about one in a book.

Baked Cod: The Path Forward in an Era of Climate Change

In recent weeks, we learned more sobering news for New England’s cod population. A paper published in Science detailed how rapidly increasing ocean temperatures are reducing cod’s productivity and impacting – negatively – the long-term rebuilding potential of New England’s iconic groundfish. The paper confirmed both the theoretical predictions associated with climate change and the recent scientific federal, state, and Canadian trawl surveys that reported a record-low number of cod caught in recent months.

To be clear, the Science authors do not conclude that ocean temperature changes associated with climate change have caused the collapse of cod. We have management-approved overfishing of cod to thank for that.

What rising ocean temperatures do seem to be doing, according to the Science paper, is dramatically changing the productivity of the remaining cod stocks. This makes it more difficult for cod to recover from overfishing today than at any other time in history, and perhaps reduces the ultimate recovery potential even if all fishing were halted. Stock assessments conducted without taking these productivity reductions into full account will dramatically overestimate cod populations and, in turn, fishing quotas.

The Science paper is potentially very important, with major implications for fishing limits on cod for decades to come, But stock assessment scientists have warned for years that their recent models were likely overestimating the amount of cod actually in the water – and the corresponding fishing pressure the stock could withstand. Unfortunately, those warnings have fallen on deaf ears at the New England Fishery Management Council.

In fact, the managers at the Council, dominated by fishermen and state fisheries directors with short-term economic agendas, could hardly have done more than they already have to jeopardize Atlantic cod’s future—climate change or not.

Overfishing, a Weakened Gene Pool, and the Loss of Productive Female Fish

As a result of chronic overfishing, New England’s cod population is likely facing what geneticists call a “population bottleneck,” meaning that the diversity of the remaining cod gene pool is now so greatly reduced that the fish that are left are less resilient to environmental stresses like increasing sea temperatures.

Overfishing has also caused the collapse of the age structure of the cod populations by removing almost all of the larger, more reproductive females (also known as the Big, Old, Fat, Fecund Females, or BOFFFS). Scientists have previously warned that losing these old spawners is a problem for cod productivity, but this new research suggests that the potential damage from their elimination may be significantly greater than imagined as a result of poor, climate change–related ecological conditions.

The Science paper hypothesizes that an underlying factor in the productivity decline of cod this past decade was the correlation between extremely warm spikes in ocean temperatures and the drop in zooplankton species that are critical to the survival of larval cod. With fewer zooplankton, fewer cod larvae make it to their first birthday.

The impacts of this zooplankton decline on cod productivity, however, could be exacerbated by the loss of the BOFFFs. Here’s why:

Cod start to spawn at three to four years old, but young females produce significantly fewer and weaker eggs and cod larvae than their older counterparts. Those elder female fish, on the other hand, produce larger, more viable eggs – sometimes exponentially more healthy eggs – over longer periods of time. If the older female cod population had still been plentiful, they might have produced larvae more capable of surviving variations in zooplankton abundance.

Perhaps the continued presence of larger, older, spawning females to the south of New England (where there is no commercial cod fishery) is one of the reasons that the cod fishery in the nearby warm waters off New Jersey is healthier now than it has been in recent history.

The Cod Aren’t Completely Cooked Yet: Four Potential Solutions

Cod have been in trouble since the 1990s, and now climate change is magnifying these troubles. This new reality, however, is not cause for us to throw in the towel. There are actions that our fishery managers can take now that will make a difference.

First, large cod habitat areas have to be closed to fishingpermanently. This is the only way to protect the large females and increase their number. Designating cod refuges such as the Cashes Ledge Closed Area as a marine national monument will remove the temptation for fishery councils – always under pressure to provide access to fish – to reopen them in the future.

Such monuments would also sustain a critical marine laboratory where more of these complex interactions between cod and our changing ocean environment can be studied and understood.

Second, managers need to gain a better understanding of the cod populations south of Cape Cod. While it is well and good to land “monster” female cod on recreational boat trips, those fish may be the key to re-populating Georges Bank. Caution, rather than a free-for-all, is the best course of action until the patterns of movement of those cod populations, as related to ocean temperature increases, are better understood.

Third, as observed in the Science paper, stock assessment models as well as guidance from the Council’s Science and Statistical Committee must start incorporating more ecosystem variables and reflecting a more appropriate level of scientific precaution in the face of the reality of climate change shifts. Enough talk about scientific uncertainty and ecosystem-based fisheries management; action is needed, and science should have the lead in guiding that action.

Finally, the importance of funding data collection and fishery science is evident from this important Science paper, which was supported by private, philanthropic dollars. NOAA should be undertaking this sort of work – but it is not in a position to even provide adequate and timely stock assessments, because limited funding forces the agency to use the existing outdated models.

NOAA’s funding limitations are constraining both collection of the essential field data needed to understand our changing world as well as the analysis of that data into meaningful and appropriate management advice. If Congress can find $33 million to give fishermen for the most recent “groundfish disaster,” it ought to be able to find money to prevent such avoidable disasters in the future.

Ultimately, the Science paper shines some much needed light on our climate change–related fishery issues in New England, but we can’t let it overshadow decades of mismanagement or justify a fatalistic attitude toward cod rebuilding. Steps can and must be taken, and fishery managers are still on the hook for the success or failure of our current and future cod stocks.

Zooplankton: A tiny creature with a big role in the cod crisis

One of the North Atlantic’s smallest ocean critters is making big waves in New England.

Centropages. Photo courtesy NOAA
Centropages. Photo courtesy NOAA

Over the last decade, we’ve seen the collapse of our iconic Atlantic cod fishery due to extreme overfishing. Now, a new study is showing a potentially disastrous link between the effects of climate change and the ailing species’ chance of recovery.

Warming waters are bound to be bad news for a cold water fish, but the problem goes much deeper than that, affecting the entire life cycle of the species. Some of this is due to tiny, microscopic creatures called zooplankton. So what are these little guys, and why are they so important?

Zooplankton is a categorization of a type of ocean organism that includes various species, including Pseudocalanus spp, and Centropages typicus. These two species happen to be the major food source of larval cod in the Gulf of Maine.

Zooplankton, which are usually smaller than 1/10 of an inch, play a major role in the Atlantic’s food web. When there are lots of them, things are pretty good. Young fish prey on them and grow to be healthy, adult fish.

But when there aren’t enough plankton to go around, species like Atlantic cod can suffer. When cod larvae aren’t easily able to find the food they need to grow, fewer of them make it to their first birthday.

And without lots of cod that survive to be at least 4 years old (the age at which females begin spawning), the recovery of the entire stock can stall. The stock needs larger, older, more productive females to thrive in order to have any hope for recovery.

Warming and shifting

But why would the plankton be in such short supply? This is where climate change comes in. According to NOAA, temperature changes can cause the redistribution of plankton communities. In the Gulf of Maine, scientists have found fewer plankton in the same areas where cod populations have been found to be struggling. The shifts in temperature lead to the displacement of a critical food source, making it difficult for young cod to survive.

Larval cod. Photo courtesy NOAA
Larval cod. Photo courtesy NOAA

With the Gulf of Maine is warming faster than 99% of ocean areas, this is an enormously alarming problem. More temperature changes and the shifting of plankton populations could make it even harder for New England cod populations to return to healthy, sustainable levels.

While the cod crisis is the result of many factors – but the loss of tiny zooplankton is a big problem. When considering how to best help cod stocks recover, fishery managers must take into account the effects of climate change, or else risk the total collapse of the species.

National Seafood Month: The Power of the Local Consumer

October is National Seafood Month! To celebrate, I spoke with Andrea Tomlinson, General Manager of New Hampshire Community Seafood, an organization committed to supporting the state’s

Andrea Tomlinson, General Manager of New Hampshire Community Seafood. Photo courtesy NHCS
Andrea Tomlinson, General Manager of New Hampshire Community Seafood. Photo courtesy NHCS

fishing industry and ensuring community access to fresh, locally caught seafood.

We hear a lot about sustainable seafood in New England, but what does it really mean, and how can we, as consumers (and seafood lovers), impact the future of the fishing industry – all the while eating more healthy fish?

AY: What is “sustainable seafood”?

AT: I think few people understand what it really means – as more people use the term, it seems to have lost meaning. For me, sustainable seafood simply means that our fishermen are only taking an amount of a particular population that does not prevent parent fish from reproducing at the same level the following year. If fishermen leave the pregnant and older fish alone, and take just the younger fish, it’s more likely to be sustainable. The fish population must be able to sustain itself while also being fished for commercial purposes.

AY: Do you think most of the industry fishes this way?

AT: No. In the past, it was a free for all. Fishermen took whatever they wanted — cod was our fish, there was lots of it, so we took lots of it. Today, our small New England fishermen are still fishing the same amount (and taking the parent fish), but there are other, bigger players in the game. Once cod was shown to be a successful industry, the number of fishermen increased – and now the populations are suffering because of it.

Our local fishermen never had to be conscious about [the amount they could catch] before. In order to stay in business, you want to take the biggest and most fish you can. When you take this traditional way of fishing and compound it with new catch regulations (and a perceived lack of communication from those enforcing the regulations), and more and bigger players fishing in the area, that’s how we ended up where we are today, with the fishing industry in crisis.

AY: What are “underutilized fish” (formerly called “trash fish”) and how could they help the industry and/or economy?

New England is home to an abundance of the spiny dogfish shark. Photo courtesy of NHCS
New England is home to an abundance of the spiny dogfish shark. Photo courtesy of NHCS

AT: In New England, there are certain types of fish that we have a lot of, but that just aren’t as popular as cod or haddock. There’s the dogfish shark, which is a shark but they are small – about

three-and-a-half to four feet in length. In Europe, they are commonly used in fish and chips. Here in New England, we have lots of it. So much so, that they are almost considered overpopulated, making it a great alternative for consumers, especially since whatever you can do with cod, you can do with dogfish.

AY: But it doesn’t have quite the same ring to it.

AT: Right. When people hear “shark” and “dogfish,” they don’t like that. But as soon as you tell them how to prepare it, and that it holds up well in the freezer, and it seasons well, and is cheap – that makes a difference.

AY: Are there other underutilized fish in New England?

AT: There’s the King Whiting, a type of Silver Hake. It’s a delectable, thick, firm white fish that’s high in protein and omega-3s. It’s good for grilling or sautéing, and the fillet is just as large as one from a cod or haddock. And there’s also the Monkfish, which is an incredibly scary-looking fish on the outside – and delicious on the inside. We hear it called the “poor man’s lobster.” It tastes just like lobster, but for a fraction of the price.

AY: How does a Community Supported Fishery work? Is this model feasible in other places?

AT: The way fishing in New England works now, most fishermen sell everything they catch all at once at an auction, instead of buying directly “off the boat.” So, as a Community Supported Fishery, or CSF, New Hampshire Community Seafood gives the fishermen an incentive – we’d give them, say, an extra $0.25 per pound of a certain fish that’s higher than what they would receive at an auction. For dogfish, it’s actually a $1.10 per pound incentive! A CSF is really the only way to buy off the boat now. We buy a small portion of what the local fishermen catch, but it’s something.

There are about 50 CSFs in the United States. On land, we’ve seen a growing popularity in supporting the local farmer, and this fits in well with that model. You pay up front, and get what’s ripe each week – it works the same way with fish. Community members can support local fishermen and the local economy in this way. So, the challenge is to get people to realize that underutilized fish are just as delicious as cod and haddock.

In New England in particular, when people hear that the fishing industry is in crisis, that affects them. Many who grew up here are enamored by our iconic fishing traditions – maybe they have good memories of fishing, or they feel that it’s a big part of the culture. When you add in the “locavore” mentality, as well as those who are trying to eat healthier, we see a real opportunity to appeal to a lot of people.

AY: So consumers can have a real impact here.

AT: Yes. The fish are there – all we need is more consumers and more buyers, and it can make a greater impact. We are also working with restaurants and chefs; they will buy underutilized fish and put it on the menu, creating more exposure and making it easier for consumers to try something new. Right now we are in 10 restaurants and a hospital cafeteria, and are continuing to expand.

AY: How can people get involved?

AT: We are mostly based in Portsmouth, NH, but our CSF has 17 pickup locations in New Hampshire, one in Northern Massachusetts, and we’re partnering with Monadnock food cooperative in Keene, NH. (All of these are listed on the New Hampshire Community Seafood website). We also have a newsletter that informs locals about what’s new, how to cook underutilized fish, recipes, and more.

AY: Anything else you would like to add?

AT: Three years ago, there were 26 local fishermen in New Hampshire, and now there are only 9 left. We buy fish from all of them. The industry is in desperate need of support, both from communities and from the NMFS [regulators].

In addition to community-supported fishing organizations like NHCS, the Gulf of Maine Research Institute’s Out of the Blue series aims to educate the public about abundant fish that are well-managed and are not harvested primarily due to low market demand.

And NOAA recently announced the public availability of fishwatch.gov, a resource that provides up-to-date information about fish, including the ability to look up a certain fish to see where it’s available, whether it’s a smart and sustainable option, nutrition information, and more.

Would you (or have you) tried dogfish, whiting, or monkfish? Leave a comment below!

 

The Fish are Talking, but Can We Listen?

The scientists who study cod populations have tried a lot of different ways to figure out where cod aggregate and to observe their behavior, like trawl surveys, sonar, and even underwater video cameras. But recently, a team of federal and state fisheries scientists have developed a new way to observe groups of cod. Rather than watching them, they’re listening to them—and they’re hearing some pretty interesting stories that could help us protect this depleted species.

This story starts with a state fisheries employee out fishing on his day off. Three miles off the coast of Gloucester, he stumbled on a large group of spawning cod on an otherwise nondescript gravel sandbar. Recognizing the opportunity to study this unusual group of fish, researchers later returned to install passive acoustic monitoring equipment.

This underwater laboratory works in two ways—first, it records the sounds cod in the area make (cod vocalize by inflating and contracting their swim bladders, making faint grunting noises that can be difficult to hear on a recording). Second, it picks up information on the location of individual cod that the researchers catch and tag with acoustic signals. This monitoring has allowed the scientists to track where male and female cod are over time, at what depth they’re swimming, and when they’re making noise.

The researchers have already discovered some pretty interesting things about spawning cod. First, they noticed that female cod and male cod make sounds during the day, but only male cod make noise at night. This pattern reflects what the researchers saw on video—at night, male cod move from the school into smaller groups where they compete for the attention of females. That means that cod actually spawn at night, not during the day as was previously thought.

The scientists also discovered that cod tend to spawn near the surface—potentially to avoid fishing gear dragged along the bottom.

While this information about spawning behavior is interesting on its own, it could also have even bigger implications for the way we protect our cod populations. Now that scientists know what a group of spawning cod sounds like, researchers can scan the ocean—potentially with self-propelled robots equipped with microphones—to locate previously undiscovered spawning sites. As scientist Sofie Van Parijs told the Cape Cod Times, “Killing them where they spawn is a great way to drive a species to extinction.” Finding groups of spawning cod could help fisheries managers create temporary or permanent areas off-limits to fishing to protect these fish when they’re at their most vulnerable.

Scientists have already used this type of monitoring to improve the management of another iconic New England species—the endangered North Atlantic right whale. An array of underwater microphones currently listens for right whales’ distinctive, upward-swooping calls. When the whales are detected in a shipping lane, nearby vessels are alerted and diverted to help avoid a collision.

Scientists believe this technology could be similarly helpful for cod, but there are some challenges standing in the way of putting it to use. First, there is limited funding for more research. Second, there is currently no set way to include this information in fisheries management process, so scientists will have to work closely with managers to see if it can be considered when setting up new areas closed to fishing. Lastly, the oceans are noisy. Between all the sounds made by other marine animals and the deep rumbles of commercial boats, it can be difficult for microphones and scientists to hear the noises cod make.

If these problems can be resolved, the quiet grunts of cod could mean a big step forward for the conservation of this depleted species.

A Tale of Two Cod

The almighty cod – the most legendary fish in our New England waters. Atlantic cod is greyish-green, and a renowned dweller of the Gulf of Maine. It is a staple of our traditional cuisine and a historic driver of our economy. You‘ve seen an Atlantic cod, right? But have you ever seen a red Atlantic cod?

How the red cod got its color is a mysterious tale, and one that even dedicated Gulf of Maine fish researchers don’t fully understand yet. Red cod live throughout the North Atlantic, in discrete populations. The red cod you see in these photos, pictured along with the traditionally colored “olive cod,” live on Cashes Ledge, about 80 miles off the coast of Gloucester, Massachusetts. They are the same species of fish, but they don’t fraternize much. The red cod and olive cod seem to be on different reproductive schedules. They also eat different things and have different ranges. Olive cod like to wander around the North Atlantic, but red cod tend to hang out in one place – “shallow, kelpy habitats,” according to Graham Sherwood, Research Scientist at the Gulf of Maine Research Institute in Portland, Maine. Shallow and kelpy is just where Brian Skerry found these red cod – in fact, in about 40 feet of water. Well, it was shallow for cod, anyway.

Why are they red? The food red cod eat, things like crabs, lobsters, and worms, are high in carotenoids – naturally-occurring chemicals which give the fish the ability to turn red. Not all cod that eat these things turn red, though – deeper dwelling olive cod remain traditionally cod-colored even on a high-carotenoid diet. Sherwood speculates that there might be an adaptive advantage to the red coloring for shallow-living cod. Perhaps the shallow water cod need better U/V protection. Or, more likely, it makes it easier to hide in all that red kelp.

There haven’t been any studies yet to indicate whether or not red cod are genetically distinct from olive cod. It’s possible that a red cod and an olive cod could come from the same parents, but be different in appearance and behavior due to having hatched in different habitats. One deeper and darker, one shallower and kelpier. Possible, but unlikely, says Sherwood. He thinks that, while they are the same species of fish, they may be genetically different enough to look and behave distinctly from each other. Maybe different populations of cod began spawning at different times, to take advantage of optimal environmental conditions, and over time they differentiated into the red and olive types. But, nobody knows for sure yet.

The color and habitat preference aren’t the only differences between the cod. Red cod are less streamlined than olive cod – no need to be shaped like a sports car if you’re just going to hang out in the garage. They also have shorter snouts than olive cod. Although, says Sherwood, if it weren’t for the color difference you would have a hard time telling them apart. Maybe because these fish tend to be homebodies, hanging out in remote places like Cashes Ledge, or in shallow inshore waters that are not targeted by fisheries, we’re less likely to run into them. Brian, a 35 year veteran of diving in the Gulf of Maine, says they are unlike anything he has ever seen.

The red cod are just one example of the amazing biological diversity that is found at Cashes Ledge. We can’t wait to show you more as our Ocean Odyssey continues!