Exercise 1: Introduction to Fish Identification and Systematics

Fish Ecology and Conservation Lab
University of Virginia, Fall 2003
Exercise 1: Introduction to Fish Identification and Systematics
Reference materials: Study of Fishes (you received a copy of this on Thursday) and
various taxonomic keys from Jenkins and Burkhead (available in lab).
Objectives: In the first part of this exercise, you'll learn how to assess (measure, count, or
otherwise determine) characters that are useful in identifying Virginia freshwater fishes
to family, genus, species and even subspecies. Those characters include various
morphological and morphometric aspects of bodies, fins, mouths and scales. You'll then
apply this knowledge as you begin keying fishes to family and to species.
In working through this exercise, you'll start becoming familiar with fish morphology,
and variations in morphology both within and among species. That familiarity will be
useful to you throughout the semester, in several different ways, including an
appreciation of the relationships between morphological traits and the distribution of
fishes in habitats and microhabitats. This exercise will also serve as a significant first step
to getting a handle on systematic relationships among fishes and on fish taxonomic
Six stations are set up at the front of the lab, with representatives of one species at each.
Esox niger (Chain pickerel; Esocidae)
Nocomis leptocephalus (Bluehead chub; Cyprinidae)
Noturus insignis (Margined madtom; Ictaluridae)
Oncorhynchus mykiss (Rainbow trout; Salmonidae)
Cottus bairdi (Mottled sculpin; Cottidae)
Ambloplites rupestris (Rock bass; Centrarchidae)
Forceps, probes and latex gloves are available in the front of the room. A light
microscope is set up on one of the benches. The fishes are preserved in 50% isopropanol,
but there is a trace of formalin present (it was used to initially fix the tissue, but was then
leached out almost entirely in a water bath); wear latex gloves when handling the
specimens. I hope you are able to schedule a time to meet in the lab with Devin or Linda
so that they can help you with the exercise. If that's not possible, please meet with me so I
can give you some preliminary pointers on handling and care of the specimens in our fish
A. For each of these six fishes, determine body form (figure 3), mouth positions and
orientations (figure 3) and caudal fin type and shape (figure 5).
For all fishes, be able to identify the characters shown in figure 4; fins, spines, rays,
barbels, body regions and areas of the head (cheek, opercle, snout). Note that not all
specimens bear all the characters shown in figure 4. For instance, only Noturus insignis
and Nocomis leptocephalus are barbeled (and are very small in the former), only Noturus
insignis and Oncorhynchus mykiss have an adipose fin, only Ambloplites rupestris and
Cottus bairdi have both a spinous and a rayed dorsal fin, and only Cottus bairdi, Noturus
insignis, and Ambloplites rupestris have spines in the leading edge of various fins.
B. Perform the following morphometric counts (see figure 7 and be sure to read the
accompanying text) for the species indicated:
-Count of lateral line scales for Nocomis leptocephalus
-Counts of scale rows above lateral line and scale rows below lateral line for Ambloplites
-Count of anal fin rays for Ambloplites rupestris
C. Observe (see figure 8) the canals of the cephalic lateralis system and parts of the head
in Cottus bairdi
Read the section on using the keys in Study of Fishes. Then use the Key to Families of
Fresh Water Fishes of Virginia to identify the species at each of the stations to family.
Key Ambloplites rupestris to genus, using Jenkins and Burkhead's Key to Sunfishes.
Note that Cyprinids can easily be distinguished from Catostomids based on a count of the
dorsal fin rays, as is described in the key -- there is no need to look at internal characters
in order to make this determination. Also, when using the Key to Sunfishes, you'll
eventually reach a couplet in which you're asked to count gill rakers. I dissected away
the left opercular flap from one of the specimens of Ambloplites rupestris in the jar so
that you can easily make that determination.
If you would like to key out some unknowns, let us know and we'll set some up for you!!