Fish - eries

There's been a lot written in recent years about the plight of the world's fisheries.  Many of them are in real trouble as the result of overfishing.  One result has been a shift toward reliance on invertebrates like prawns, lobsters, and mollusks.  New research from the Environment Department at York suggests that these new, shellfish-dependent fisheries, may be subject to collapse with increasing stress from climate change.  The authors, in a paper appearing in Fish and Fisheries, suggest that it's imperative that we continue to work toward restoring the health of finfish based fisheries, and stress the need to marine protected areas to allow the restoration of diversity and productivity.

River monsters

A big-river specialist

OK, that was just to catch my students' eyes.  They're addicted, and we do hope to do some big fish work on the Tombigbee this summer.  What I want to talk about here though is not the size of the fish, but the size of the rivers.  A new study published in Frontiers in Ecology and the Environment looks at the prospects for saving big-river specialist fish, those guys that are dependent on big waters like the Mississippi.  The authors looked at distribution patterns of big-river specialists in the Mississippi basin, and found that moderately sized tributaries, those with 166 cubic meters per second, support 80% or more of the basin's 68 big water lovers.

This could be significant for conservation efforts.  There's little that can be done to restore natural conditions to the nation's major rivers.  Perhaps we would be better served to aim some conservation dollars toward these all-important tributaries.

FYI, that 166 cubic meter per second threshold is slightly in excess of 5,000 cubic feet per second (unfortunately, those are the default units on NOAA's hydrologic data reports, like those here).  If I've done the math right, the Tombigbee at Dempolis has a flow rate, at the moment, in the area of 8,000 cfs - that's about 225 cubic meters per second.

A new semester...

...starts tomorrow, and with it we'll try once again to be a bit more active here.  This semester brings Biology of Fish, as well as an online Evolution class - a couple of topics that should lend themselves well to blogging.  Even if it means not collapsing on the couch at the end of the day.

We'll start with this an interesting study examining the evolution of disease.  That's a topic that my evolution students will look at in depth later in the semester.  This one's in birds, house finches to be specific.

Pathogenic organisms can find themselves in a bit of a quandary.  They're dependent on their host organisms for survival, reproduction, and dispersal.  But they run the risk of overdoing it.  As they reproduce, the host may become sick.  If the numbers are too exorbitant, the host may even die.  If a pathogen reproduces in such numbers that it kills or disables its host prior to spreading to new ones, it'll soon be out of the parasite business.  However, coevolution of parasite and host can result in just the right balance of "sickness".

Virginia Tech's Dana Hawley and her coauthors, in a paper published in PLOS Biology, explore the evolution of house finch eye disease, a form of conjunctivitis in the invasive house finch caused by the Mycoplasma gallisepticum.  The researchers expected to see the disease become milder with passing time, all the better to expedite its spread.  They were surprised to see it actually become more virulent. In two different locations.

The house finch, Haemorhous mexicanus,
carrier of house finch eye disease 

What is particularly interesting in this case involves the two regions that were examined.  The study focused on birds from two different areas, California and the Eastern Seaboard.  Samples taken from sick birds in each area from 1994 through 2010 showed increasing virulence.  However, the bacterial strain the spread from east to west across the continent was less virulent.

Apparently, to spread, the bacteria needed healthier birds.  Birds that could fly a little further and live a little longer.  Once established in a location, though, more virulent strains could evolve - sicker birds may not disperse as well, but they produce lots of bacteria.

This relates to a number of other studies that have revealed some truisms about human disease.  For example, a pathogen that can be transmitted through the air or by an insect vector can afford to be more virulent than one that requires the host to be actively eating or drinking.  More to come on that.