TIME, CHANGE, AND GREEN WATER

 

There are a lot of things that might strike a person on their first trip offshore.

The vastness of the ocean, once the land falls away, can be breathtaking for some, and a little disconcerting for others. 

 There is the color and texture of the water--the bright track of the rising sun, the shadow of cloud, the patch of ripples on an otherwise calm ocean where water wells up from the bottom.

And there is the life.  Wilson’s storm petrels seemingly walking on the surface of the sea.  Dolphin racing alongside the boat, sporting in the bow wave.  Maybe a leatherback turtle, or a basking shark or, ever more often, a breaching humpback whale.

For me, the most striking thing on my first trip offshore was the water’s clarity.

I grew up on the shores of Long Island Sound, in the age where even secondary sewage treatment was never a given in come neighboring towns.  Fed on a rich soup of nutrients from sewage plant outfalls, and fertilizers flowing from the manicured lawns of shoreside estates, the Sound I knew as a boy was rich with phytoplankton; even as a six-year-old standing in knee-deep water at the town beach, there was no guarantee that I would still see my toes.

I started fishing on party boats in my sixth year.  Some of the trips were in Cape Cod Bay, in search of its namesake finfish; it’s possible that other trips were in the ocean, but if they were, they were in the plankton-rich sea off Provincetown, Massachusetts which, although clearer than Long Island Sound, still hid any fish that weren’t just beneath the surface.

My first unquestionably pelagic trip took place in May 1968, when my father allowed me to join him and two of his friends on a cod trip to Cox’s Ledge, off Rhode Island.  Back then, boats were slow, and it probably took our wallowing party boat two and a half hours to make the 20-something mile trip.  I remember sitting on the doorframe of the cabin—the boat didn’t have any outside seats, and the cabin was filled with the smells of cigarettes and early morning beers—watching waves roll in from an empty horizon, telling myself that seasickness was only a state of mind (and successfully defeating the queasiness brought on by the long, oily swells that were a new challenge for my inner ear to overcome).

It didn’t take long, once we reached the grounds, for someone to hook up with a fish, and I remember staring down into the ocean, watching the cod come up toward the surface, first as a barely-seen greenish-blue glow many feet down, then slowly taking on shape and form and finally color as it was brought within reach of the waiting gaff.  For as long as I cod fished from party boats, I was always fascinated by watching fish materialize out of the depths.

After I began fishing offshore for sharks, billfish, and tuna, I began to be even more conscious of clear blue water.  Marlin pretty well insisted on it, as did most of the tunas, although bluefin would, if the bait was there, often come into the murk.  It didn’t matter so much for sharks, but even so, we always noted the color as we ran offshore; our wake was almost always a clear, pale blue before we reached our destination.

Just like on the cod boats, staring into the deep remained a fascination.  We could see our close-in bait, set 30 or so feet below the chum can, flashing in the sun, and often spotted a sleek blue shape cruising somewhere above or below it, letting us to place the bait right in front of the fish. 

On one occasion, fishing south of Shinnecock near the Coimbra wreck, we noticed a strange fish about two and a half feet long, cruising around in our chum slick.  We couldn’t figure out what it was, until it finally came up to the can, and we realized it was an unusually large remora.  Speculating about what might be large enough to host such an animal, we were looking over the side as a light bluish patch began to appear below the boat.  It’s shape—it seemed sort of roundish—confused us, and led to speculation that it might be a turtle, or perhaps a sunfish (Mola mola), but neither of those felt quite…right.  We were caught a little off guard when, a little closer to the surface, the image resolved itself to be a white shark, which we eventually estimated to be about 13 feet long, coming straight up, just like the notorious shark on the book cover did fifty years ago.  Maybe four feet below the surface, the shark switched to a horizontal plane, made one fast pass through our slick, and disappeared.

Seeing down through the clear water brought us many similar sights, although none that were quite as dramatic.  But as the years passed, it slowly seemed that the clear water was receding.  White marlin and yellowfin tuna were no longer coming too close to shore.  Often, when we were fishing for sharks, we couldn’t see a hooked fish even when we already had the other end of a 15-foot leader in hand.

Yes, we sometimes had clear-water days, but they were ever less frequent, and the water was never quite as blue as it had been three decades ago.  Often, we’d even find green water out past the 30 fathom line, where it once, almost always, ran clear.

But the change had come slowly.  The first green-water year we remember was 1985, when the chlorophyll remained thick all the way out to Hudson Canyon.  But that was an oddity.  With the dawn of the new century, it felt like green water was becoming ever more common.  Yet, because change was slow, we always had to ask ourselves whether it was really there, or just misperception.

Apparently, our perception was true.

A paper, titled “Global climate-change trends detected in indicators of ocean ecology,” was published on July 12 in the journal Nature.  It reported that

“Ocean colour satellites, which measure the amount of light radiating from the ocean and atmosphere from Earth’s surface, have been collecting global measurements for decades.  A great deal of research has focused on long-term trends in ocean-colour data, particularly in chlorophyll a (Chl) and primary productivity over large regions.”

The referenced satellites are the same ones used by providers of the ocean color and temperatures charts that offshore fishermen use to find water most likely to find pelagic fish, and are not unfamiliar to anglers. 

The paper went on to note,

“the MODIS sensor aboard the Aqua satellite (hereafter, MODIS-Aqua) has far surpassed its originally planned mission duration of 6 years, having just completed 20 full years collecting high-quality global ocean-colour data.  The key variable provided by MODIS-Aqua (and any ocean-colour sensor) is R_rs, which is the ratio of water-leaving radiance to downward irradiance incident on the ocean surface…Similarly to Chl, R_rs is an indicator of the state of the surface-ocean microbial ecosystem…Again similarly to Chl, trends in R_rs…do reflect changes in surface-ocean ecology…as Rrs does encode combined information about surface ecosystems and dissolved and particulate organic matter, any trend in R_rs reveals notable changes in the components of surface-ocean ecology and biogeochemistry with optical signatures.  Furthermore, any change in R_rs corresponds to changes in the light environment itself, which will affect phytoplankton and thus ultimately lead to ecosystem changes.”

In discussing the study’s findings, the paper noted that

“To investigate possible trends in ocean colour, we performed…an autocorrelation-corrected multivariate regression on the first 20 years of MODIS-Aqua ocean R_rs data, spanning July 2002-June 2022.  We find significant trends…in 56% of the ocean, primarily equatorward of 40^o.”

The waters where we fish offshore of Long Island just happen to be right around that 40^o boundary.  Thus, our observations of greener water are most likely correct.  However, if an angler just began fishing for sharks, billfish, and/or tuna around the year 2000, that fisherman would never have known the crystal blue water that we commonly fished in during the 1980s and ‘90s, and would believe that today’s chlorophyll-tainted ocean represented the long-term state of the sea.

It's a twist on the so-called “Shifting Baseline Syndrome” first described by biologist Daniel Pauly, who noted that

“each generation of fisheries scientists accepts as a baseline the stock size and species composition that occurred at the beginning of their careers and uses this to evaluate changes.  When the next generation starts its career, the stocks have further declined, but it is the stocks at that time that serve as a new baseline.  The result obviously is a gradual shift of the baseline, a gradual accommodation of the creeping disappearance of resource species, and inappropriate reference points.”

Although Dr. Pauly referred to “fisheries scientists,” his comments hold equally true for fishermen.  A fisherman judges the health of fish stocks by comparing them to the state of stocks when that person began fishing.  If there are more fish around than there were when an angler began his or her fishing career, than they’re likely to say things like, “There are more [name a species] around than ever before,” when, by long-term historical standards, fishing is actually mediocre. 

Similarly, anglers who never experienced a stock collapse are more likely to panic when a fish population declines, and call for draconian measures when, in fact, fish remain reasonably abundant and are only in need of modest additional protections.

Thus, whether talking about fish populations or ecological conditions, both scientists and fishermen need to maintain a broad temporal perspective.  That old guy talking about how good fishing used to be may not be merely romanticizing the past, but is instead providing a very important point of reference.

I was thinking about that again the other day, as I was speaking with a young scientist who was collecting samples and data from sharks caught aboard my boat.  We were talking about her doctoral dissertation, which is going to address the historical abundance of a number of different fish species, when she observed that a lot of fisheries tanked at the same time, quite a few decades ago.  Her comment struck me, because her findings, like the recent study on ocean color changes, precisely matched my memory of the patterns of abundance in many northeastern fisheries.

The difference was that I was there, experiencing the declines, while she came to the same conclusions that I did second-hand, by analyzing a wide array of available data.  The virtue of that hard data, of course, is that it validated my memories, sharply reducing the chances that they are merely the result of a selective memory.  I hope to have a chance to read the completed work once it is done.

Unfortunately, a lot of people won’t get a chance to read it, and wouldn’t even if they could.  They will go on believing that their lives encompass the entire relevant history of our fisheries, that they have known the best times and maybe the worst, and that a depleted fishery very possibly represents the best that such fishery can ever be.

Whether we hear them talking about striped bass, red snapper, summer flounder or, maybe, even cod as “the best fishing that has ever been,” we need to understand their limited frame of reference.

For we can make things better.  We can rebuild depleted stocks.

But before we can do so, we first need to admit that, when viewed in a historical context, a problem really does exist.