Posts Tagged ‘blueback herring’

Floodplain Fish

July 31, 2017

River systems host a hidden world of tiny invertebrates.  Some are microscopic, while others, though visible to the naked eye, remain unseen unless a curious fisherman cuts open the stomach of his catch.  A fish’s stomach might contain small crustaceans including water fleas (Cladocera), seed shrimp (Ostracada), amphipods, copepods and/or isopods.  These minute shrimp-like creatures form the basis of a food chain that supports fish populations.

Image result for Ostracod

Seed shrimp (Ostracods) along with other small crustaceans are an important part of the food chain in aquatic habitats.

In southeastern North America rivers overflow their banks between November and March because cooler temperatures reduce evapotranspiration and dormant riverside vegetation takes in less water.  The flood stage is especially wide in the flat coastal plain region where a sheet of water 2-3 feet deep can cover hundreds of square miles alongside major rivers, though modern dams, ditches, and canals have reduced the former extent of these flooded wetlands.  This flooded land offers more territory for fish to forage and reproduce.  The diet of many fish species changes from the aquatic crustaceans mentioned above to prey that normally lives some distance from the river.  1 study found fish occupying floodplains ate a species of isopod that lives in small pools of water, terrestrial species of crayfish, beetle larva, and caterpillars.  These terrestrial species were not normally found in fish’s stomachs until the flood stage.  Some species of fish even breed over floodplains that become dry land during summer.  The blueback herring (Alosa aetivalis) spawns in flooded hardwood swamps, unlike its relatives the American shad and hickory shad that spawn in the main channel and tributaries of a river.  Blueback herring eggs adhere to twigs on the forest floor.

 

Blueback herring spawn over flooded land.

White bass (Morone chrysops) also spawn on floodplains during high water.  This species is probably the “white fish” mentioned by John Lawson in his book A New Voyage to the Carolinas.  A few years ago, I wrote a blog article identifying the fish Lawson wrote about in his early natural history book.  (See: https://markgelbart.wordpress.com/2014/08/31/identifying-the-species-of-fish-described-by-john-lawson-in-1710-part-2/   )I was able to figure the identity of most of them despite the archaic names and vague descriptions, but his “white fish” stumped me.  Zach Matthews, editor of The Itinerant Angler, suggested to me that Lawson was referring to the white bass.  Lawson’s description that it was found in “freshets” or floodwaters is good evidence he was discussing the white bass.

Image result for white bass

White bass also spawn over floodplains.  This is probably the “white fish” John Lawson discussed in his book A New Voyage to the Carolinas.

There have been plenty of genetic studies of the white bass and its cousin the striped bass because the 2 closely related species are hybridized for sports fishermen.  But I can’t find any genetic studies that explore the evolutionary origin of this genus.  It seems likely white bass diverged from the same ancestor as the striped bass, and this common ancestor was probably an anadromous fish, like the latter species. The initial ancestral population of white bass began spawning on floodplains and became landlocked and unable to return to the ocean when something temporarily blocked access to the ocean.   This explains how the 2 species diverged from each other.  White bass evolved the ability to survive entirely in freshwater habitats and were able to colonize aquatic environments much further inland than striped bass.  White bass collect fat reserves and can endure cold winters.  They became well adapted to the colder temperatures of Pleistocene Ice Ages.  Geneticists could probably use a molecular clock to determine when this divergence occurred, and they may be able to tie the timing to some climatic event.

Fish use floodplains to migrate to new habitats and maintain genetic vigor between populations.  During flood stages many fish from the Okefenokee Swamp swim through flooded habitat to the Suwannee River.  Warmouth, flier, bowfin, pickerel, bullheads, and lake chubsuckers have all been recorded traveling through 2-3 feet of water to the river.  Floods can also connect breeding fish from oxbow lakes with fish from the main branch of the river.  Shiners, bream, catfish, darters, mosquito fish, and starhead minnows often travel through flood waters between oxbow lakes and rivers.  Eels also use these corridors but they don’t breed in freshwater.  Many fish get trapped in oxbow lakes and sloughs after floodwaters recede.  However, oxbow lakes provide better habitat for fish than rivers, often holding 12 X more fish per acre though species diversity is identical.  The most common fish in Altamaha River oxbow lakes are gizzard shad, spotted sucker fish, and channel catfish.

During Ice Ages rivers in the southeast didn’t flood as much as they do today.  The fish best adapted for braided river patterns were most common.  Cut-off channels within river beds probably held concentrated populations of catfish and killifish.  Anadromous fish such as shad and striped bass spawned in areas that have since been inundated by rising sea levels.  Following the end of the Ice Age, there was a supermeandering phase of rivers when flooding was more extreme than it is today.  This caused a resurgence of floodplain fish species.

Reference:

Clark, J.R.; and J. B. Forado

Wetlands of Bottomland Forests

Proceedings of Bottomland Hardwood Forest Wetlands in Southeastern United States 1980

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Black Bears Catching Shad–A Forlorn Scene of Nature

March 6, 2014

Many nature scenes, common just a few hundred years ago, shall never be seen again.  Some examples of forlorn nature scenes from Georgia that I’ve discussed on this blog include herds of elk and bison grazing on surpentine barren hilltops, flocks of migrating passenger pigeons darkening the sky, a forest of gigantic black oaks with each tree measuring between 8-11 feet in diameter, stands of bamboo cane covering many square miles, a river full of spawning sturgeon, etc.  The thought that these scenes will never exist again gives me feelings of melancholy and loss.  One other nearly forgotten scene would be when black bears caught spawning shad in rivers of eastern North America.  This no longer occurs because black bears have been extirpated from regions where shad still spawn.  Black bears probably preyed upon spawning shad and other species of herring for at least 1 million years, but man completely ended this ecological relationship.  For nature lovers this is just sad.

Illustration from John Lawson’s New Voyage to South Carolina, published circa 1710.  Lawson reported black bears regularly catching spawning shad in eastern rivers and such a scene is depicted in the left lower corner of this illustration.  Black bears have been extirpated from regions where shad still spawn.

Black bear (Ursus americanus).  Formerly common for over a million years, it has been eradicated from most of is original range.

Alaskan brown bears (Ursus arctos) are often filmed catching salmon is remote wilderness areas.  Therefore, nature lovers associate a bear catching a fish with wilderness.  That eastern North America was once just as wild as Alaska seems to be largely forgotten or never thought upon by most people.

John Lawson, an early English explorer and settler of the Carolinas (1700-1711), took note of the black bear’s habit of catching shad and herring during their spring runs. Bear was his favorite meat.  He highly praised the culinary properties of bear meat and fat, but he warned his readers not to eat them during spring when the bruins were gorging upon herrings, for then they tasted “filthily.”

The American shad is in the herring family.

The American shad (Alosa supidissima) is a member of the herring family.  It is an anadromous fish, living most its life in deep ocean waters but swimming up freshwater rivers to spawn in the spring.  Adults that spawn in northern rivers survive and swim back to sea, but those spawning in southern rivers die after spawning.  The eggs, laid on sandy pebbly bottoms, hatch after a week, and the fingerlings make it to the ocean by fall.  A female shad can lay up to 150,000 eggs.  Shad feed upon plankton, small shrimp, and other fish’s eggs, and they will bite during their spawning run, unlike salmon.  Two other species of herring spawn in eastern rivers–the blueback herring (Alosa aestivalis) and alewife (A. pseudohorega).

Herring are rich in the healthy kind of fat.  The Exxon Valdez oil spill in Alaska destroyed stocks of herring there, and marine life has since struggled to recover.  There are far fewer seals in Prudhoe Bay, even though pollock (the fish most often processed into fish sticks) is still abundant.  Pollock just doesn’t have the nutritive quality of herring.

Planked shad and shad roe with bacon is considered a classic American dish, but I’ve never had the opportunity to eat it.  Herring reportedly have many small bones that make them difficult to eat.  The vinegar in marinated herring dissolves these small bones.  I do enjoy marinated herring on occasion.  I’ve read that some cooks slash the herring and deep fry their slashed fish.  The hot oil supposedly seeps into the slashes and melts the small bones.  I have eaten bream eggs…they taste just like chicken eggs, though a little more bland.  To prepare, drop the fish eggs in boiling salted water for a minute.  Remove with a slotted spoon and serve on toast rounds with mustard.  Expensive caviar pretty much tastes like fish guts but when mixed with cream cheese I can get it down.  Boiled bream eggs are better.