The Pogey-Plankton Ecosystem

Considering that I haven't directly encountered either pogies or plankton, I'm astounded to learn how influential they are in the makeup of our biosphere.

Phytoplankton

Plankton escape our notice because they are microscopic though super-abundant in the ocean. Some are plants, the phytoplankton, and some are animals, the zooplankton. Zooplankton ultimately depend on phytoplankton because they are the ones that turn sunlight into organic life and form the very foundation of the food chain. Marine animals diversify up from zooplankton through a complex of carnivorous predators that eat other flesh. 

Pogies are one of the relatively few vegetarian species of fish. As adults they prosper almost exclusively on phytoplankton. They don't bite anything. They're able to harvest those myriad algae and other miniscule drifting plants by passing them through a filtering system in their gills. They are able to digest celluloids profitably perhaps like our grazing ruminants which rely symbiotically on gut bacteria. Pogies have nearly cornered the market on their food source, although oysters and mussels in the estuaries, and some huge marine mammals like basking sharks and baleen whales are also filter feeders, though these creatures don't appear to discriminate between phytoplankton and zooplankton. 

Operating with a seemingly limitless food source and tremendous individual fecundity, pogies became far and away the most prolific fish along the Atlantic coast, despite being devoured by almost everything that could swim, fly or dive where they congregated. We've seen how, despite being prodigiously netted for farming soil enrichment, they still sustained the multitudes of fisheries dependent on menhaden in their diet. Even in fairly modern times author and observer Bruce Franklin refers to "that living river of menhaden [that] flowed with the seasons north and south...many miles wide along the coast, [yet filling] bays and estuaries from Florida to Maine with almost solid flesh." He relates the testimony of a sea captain in the 1870s who reported to the Fisheries Commission that "I saw a school of menhaden out at sea, when I was going to Portland, that was two miles wide and forty miles long." ¹ 

As capital investment and technology rendered the pursuit of menhaden into an industrial commodity, the species was annihilated in the northern part of its range. Eben Phillips' fish oil factories closed. Fleet operations necessarily shifted South and are now almost entirely owned by a single corporation located in the Chesapeake Bay. One of the complications to management of the fishery is that menhaden spend much of their lives within three miles of the shore, where waters are supervised by State agencies with parochial interests.  The incentives, particularly with regard to migratory fish, are to catch all you can when they pass by, and blame other regions for the demise. The National Marine Fisheries Service tries to coordinate policy beyond inshore territories out to the 200-mile limit.

Trends in Menhaden catch, 1940 to 1967 ¹

One consequence of the decimation of menhaden is the unchecked growth of phytoplankton, "that inconceivable mass of rootless plants that drift about in the sea with little or no control of their own locomotion." The phytoplankton take different forms, much of it one-celled algae. Nutrients flowing from continental land and rivers make estuaries and coastal waters especially rich environments for phytoplankton. Left unchecked‒as has occurred periodically in the North Atlantic and is now threatening the Chesapeake Bay‒the dense bloom of phytoplankton growth can block sunlight, reduce oxygen, toxify waters, smother bottom-dwelling shellfish, and lead to eutrophication of coastal zones.

The tragedy of the commons was formulated as an economics problem, but it portends an ecological problem as well with consequences for the livability of the planet. The tragedy of the commons reveals an outcome where individual incentives to consume a resource, acting in their apparent own self-interest, results in harmful over-consumption to the depletion and detriment of all. Solutions to the tragedy of the commons include the imposition of private property rights, government regulation, or the development of a collective action arrangement.

Advocacy for federal intervention in the United States has of course collided with a very strong inclination toward individual freedom. Since the beginning of resource administration in the 1870s, fisheries management has been assigned to the Department of Commerce rather than the Department of the Interior, with an orientation to sustaining harvests. Advocacy has featured many voices with competing perspectives and interpretations of data. One principle is clear about ecological relationships: pressure on any one part affects others. Human activity and welfare are very much part of the equation.

The Ipswich Bay and Folly Point, looking west from Halibut Point 

¹ Chart and information derived from Bruce Franklin's The Most Important Fish in the Sea, 2007.