Wednesday, February 16, 2011

Field Notes: Barrens topminnow survey and collection

It may still be February, but the temperature has warmed and we're headed outside!  Yesterday, we joined staff from the Tennessee Aquarium for a day of field work to survey and collect Barrens topminnows (Fundulus julisia)- we call them BTMs for short.  We are some of the partners in an ongoing restoration effort for this imperiled Tennessee endemic species, a project that is unique in the amount of cooperation we have with private landowners, government agencies, and other nonprofits.

An adult male BTM.  Image courtesy of CFI

We met up with biologists from the US Fish & Wildlife Service and Conservation Fisheries, Inc. (CFI) at a site in rural Tennessee north of Manchester.  The site is a small spring and spring run that runs under a highway and through an adjacent cattle field--all on private land that we can access because of our cooperative partnership.  We split up into two groups and sampled different sections of the spring run.  For most of the length of the run the water was only a few feet across and rarely more than knee deep.  Using seines--long nets, each group made 12 hauls through different parts of the site.  All BTMs were set aside in a bucket and measured before being released after all sampling was finished.

The first group, who worked the upstream portion of the spring captured over 60 BTMs from juveniles through adult age classes.  That's a good indication because it shows there was breeding activity going at this site; a sign of a healthy population.  That same group also captured green sunfish (Lepomis cyanellus) and tadpoles in the seine hauls. 

Luckily, no western mosquitofish (Gambusia affinis) were captured this far upstream, hopefully indicating that this invasive species is not present in the spring.  Mosquitofish are a threat to BTMs because they can be aggressive towards the adults and actually prey on the juveniles.  Mosquitofish are one of the biggest continuing threats to BTMs across their entire range. 

The second sampling group was even more successful, surveying over 80 BTMs.  The second group did, however, capture mosquitofish.  Hopefully, the mosquitofish will not invade further upstream in the spring run.

Biologists surveying BTM populations in the field
We and CFI kept some of the adult BTMs from this site to use as broodstock in our ongoing captive propagation programs.

After sampling at the first site was completed, we piled into our vehicles and drove to another site a few miles north.  There, we accessed a small tributary to the same creek system that runs through a newer housing subdivision.  Pat Rakes, from CFI, recalled spotting a few BTMs during a quick visual survey of the site over a decade ago, and he wanted to see if they were still there.  Using a seine, we quickly collected a few BTMs and other small-stream fishes native to the area.  The creek appeared healthy, but the area immediately adjacent to the spring was being heavily impacted by development and will need close monitoring in the future.  A small number of fish were taken from this site, and we will use fin clips from them to analyze their DNA to see if they are a distinct population from the BTMs at the earlier site.

Thursday, February 10, 2011

For Valentine's Day: Red is the "color of the deep"

In honor of Valentine's Day, today's post is dedicated to the color Red.  For humans, we often associate vibrant hues of red and pink with love and romance.  For deep sea fish and invertebrates, this same vibrant color is actually camouflage.  As light penetrates the surface of the ocean, the higher energy, longer wavelength red light is absorbed first.  That means that as you descend more than a few meters past the surface, all the red light is quickly absorbed.  With no red light present at depth, objects that are red in color appear drab and grey. 

Visible spectrum attenuation as a function of depth.
Taken from

For animals that live at extreme depths, red becomes the perfect color for avoiding visual detection.  Furthermore, deep sea animals have lost the ability to see the color red making red colored prey (or predators) even more difficult to detect.  The Monterey Bay Research Institute (MBARI) posted a video on YouTube that shows lots of different deep sea animals which are Red in color.  Check it out!

Monday, February 7, 2011

A Fishy Valentine's Day

Flowers? A box of chocolates? Maybe a fancy home cooked meal? How will you celebrate Valentine’s Day? While many of us humans spend the week leading up to Valentine’s Day fretting and fuming over how to best impress our loved ones, a look to some of our finned neighbors might provide some inspiration…

Breeding season for many North American minnows belonging to the family Cyprinidae is marked by drastic changes in the appearance of the males. As spring approaches and water temperature warms, males of many species begin to display vibrant colors to attract mates. Many of these fish live in clean, clear water where bright colors can be effective at communicating with potential mates. In addition to changes in color and behavior, in minnow species the males begin to grow temporary bumps over their heads (and bodies and fins of some species). The exact function of the bumps, sometimes called nuptial tubercles, is not fully understood, but it is believed they are used for nest defense and for stimulation of their mate.

Males of the minnow genus Nocomis, commonly referred to as chubs or horny heads, use nest building with stones to impress their mates. Minnows of this genus are nest builders- constructing nests made first by excavating a pit in the substrate. Once the pit is dug a male will coax a female to enter the pit where mating occurs. Once the eggs have been released and fertilized the male then fills the pit with larger river stones protecting the fertilized eggs from predators and from being smothered by silt. These larger stones provide more space so clean, oxygen rich water can flow over the nest. The male then aggressively guards the nest from other fish who may attempt to prey on the eggs.