Ichthyology (Bio 261) Laboratory Instructions
Fish
taxonomy and ecology can be challenging fields of study, as fish are
often not
readily observable and most people have limited exposure to the wide
diversity
of fishes around them (this is in contrast to the flying reptiles which
are
everywhere and often a nuisance). Yet,
being the ancestral group to all other vertebrates coupled with the
sheer
taxonomic diversity within the fishes makes these creatures a joy and
wonder to
study.
The
laboratory section of this course will focus primarily on learning to
identify
by sight some of the common fish families (41) and species (42) in
I’ve
included a blank laboratory notebook sheet in this packet.
Please make your own photocopies to use in
your notebook (sorry, budget constraints prohibits me from doing this
for
everyone). Notebooks must be
three-ring binders. You are required
to complete one sheet for each of the Families listed below. You probably should not spend more than 15
minutes on each sheet.
I am not looking for works of art,
just large sketches that are
recognizable and labeled with the identifying characteristics
(dichotomous key
traits) for that taxa. Drawings must be
done from actual specimens, not books.
You should think of the notebook as your
personal study tool and treat it as
such, adding any information that will help you remember the organisms.
The
“Ecological notes” section should be used to answer, based on your
observation
of the morphology of the organism, the following questions:
1) What
type of food do these fish likely eat and why?
2) How
does this fish likely capture its food? (how does it feed)
3) What
type of habitat would you likely find this fish? (be more specific than
"the water" :-)
4) How
does this fish avoid predators?
5) What
other interesting information can be inferred about this fish's ecology
from
its morphology?
Not all of the answers to these
questions may be readily apparent from the morphology, but most of them
will. You are encouraged to infer as
much as you can about the ecology of the fishes we study and will not
be
penalized for wrong (but reasonable) guesses.
I have
provided an example of the type of work I expect. I
will happily look at your notebook anytime
throughout the semester and give you feedback on it, usually by the
next
day. Notebooks must be neat, legible,
complete and the pages numbered (sloppy, illegible and incomplete
notebooks will
receive low grades). There is no reason that anyone who wants to
get 100%
on their notebook should not succeed.
Notebooks will be collected for grading during the last regular
week of
the semester.
CARE OF FISH SPECIMENS
The majority of the fish you will examine in lab will come
from the
Fish
Families For Which You Need To Have
Drawings
(Listed in the order they should appear in
your notebook,)
Feb 16 families: Carcharhinidae, Squalidae, Rajidae, Myliobatidae, Chimaeridae, Clupeidae, Acipenseridae, Salmonidae
Feb 23 families: Amiidae, Lepiosteidae, Engraulidae, Esocidae, Aphredoderidae, Centrarchidae
March 8 Lab Practical
I
March 22 families: Osmeridae, Cyprinidae, Catostomidae,
Hemiramphidae, Cyprinidontidae
March 29 families: Ictaluridae, Scorpaenidae, Hexagrammidae, Cottidae, Moronidae, Percidae, Echeneidae
April 5 families: Poeciliidae, Cichlidae, Pholididae, Gobiesocidae, Gobiidae, Bothidae, Pleuronectidae, Cynoglossidae
April 12 Lab Practical II (COMPREHENSIVE)
Using Morphology to Infer Ecology
(Bring this with you to lab and refer to it!!)
You
might initially think that since we don’t directly observe organisms in
their
natural habitat in this class, (i.e. we pull them out of their habitat
and
bring them to the laboratory) that we are somehow prevented from
learning much
about their ecology. This is not
completely true. We do have a lot of
external
cues (morphological features) we can use to infer aspects of their
ecology and
natural history (where they live, what they eat, how they avoid
predators
etc.).
We do
this sort of thing every day in our own lives.
For example, if you saw a gentleman downtown wearing sandals,
dark
socks, bermuda shorts, a funny hat and he was snapping pictures every
five
minutes, you might infer that he was a tourist checking out the sights
of
Chico. You may be wrong, (he might have
been your instructor doing some field work), but chances are that you
would be
correct roughly 80% of the time.
This is
what I am asking you to do in the lab portion of this class. Be an astute observer, look closely at the
organisms and think about how different structures and morphology may
enable or
constrain the animal. I don’t expect you
to get everything correct all the time, but with a little logical
thinking, you
should be able to infer quite a bit regarding these organisms’ ecology. This handout explains how the body form,
size, mouth, sense organs, coloration, and protective organs can be
used to
make inferences about how particular fish “make a living.”
Throughout
the semester also try to think of how some of these morphological
features can
interact with each other (i.e. the color of small organisms etc.)
1) Body form -
What does the organism look like?
a) Rover-predator:
This is the classical fish shape with the thickest part of the
fish
about 1/3 of the way down the body. This
shape reduces drag and is designed for cruising and pursuing active
prey. It is also effective for holding
position in
fast-moving streams. Examples: tunas, trout.
b) Lie-in-wait predator: These
fish are elongate and have large
dorsal, anal, and caudal fins placed far back on the body.
This arrangement results in a lot of drag and
poor sustained swimming but gives the fish excellent acceleration for
ambushing
prey. Example: pike.
c) Surface-oriented fish: These
fish feed primarily on insects living
at or near the surface of the water. The
head is usually flattened dorso-ventrally and the mouth is
supraterminal. Such fish are usually small
and have the
dorsal fin placed far back on the body.
Examples: mosquitofish, mollies.
d) Bottom rover:
These fish are adapted for feeding at or near the bottom. The mouth is often subterminal, the pectoral
fins usually large and rigid, the head is sometimes dorso-ventrally
flattened,
and the dorsal fin short and upright.
This morphology uses the water current to keep the fish pressed
down against
the bottom. Examples: catfishes,
suckers, sculpins.
e) Bottom clinger:
These fish often have pelvic fins that are modified into a
sucking organ
to assist in maintaining position in fast or turbulent water. Example: gobies.
f) Deep-bodied fish:
This body type is designed for maneuverability.
The pectoral fins are large and high up on
the body, with the pelvic fins immediately below. The
body is laterally compressed, with the
depth up to 1/2 the body length. Fish of
this type are usually associated with some type of cover.
Their large, bulging eyes give them binocular
vision, which makes them adept at locating and “picking” their prey
items. Examples:
bluegill, surfperches.
The flounders are a group of fishes, which have adapted this body form to a bottom-living lifestyle. The lateral compression allows them to effectively hide on the bottom, making them good ambush predators. Example: halibut.
Planktivores, which are usually high in the water column and away from cover also use a laterally compressed or deep body form, coupled with sharp ventral keels and silvery scales to reduce their visibility from below. Example: herring.
g) Eel-like fish:
These fishes have reduced or absent pectoral and pelvic fins and
the
dorsal and anal fins are sometimes fused to the caudal fin. In extreme cases the operculum, maxilla, and
other protruding parts are absent. This
body type makes them able to hide in reefs, rock piles, etc. without
getting
snagged. Example: moray eel.
2) Size -How big is
the critter?
Size does matter to an organism, especially if the organism
happens to live in water. Large aquatic
organisms are confined to certain types of aquatic habitat (think of
trying to
fit a 5m sturgeon into Little Chico Creek?!).
The large size places constraints on them physically, (how do
they get
food, oxygen, mates etc.) which in turn constrains where they live and
what
they do (i.e. their ecology). Small
sizes also place constraints on organisms, especially when they are
very
small. It is always important to put the
scale on your drawings.
3) Mouth -How does
it get its food?
Mouth size is usually a good indicator of prey size (expect
in filter-feeding planktivores, which have exceptionally large mouths
and eat
exceptionally small prey). Supraterminal
and subterminal mouths characterize surface- and bottom-feeders,
respectively. Piscivores usually have
sharp teeth (which may be backward pointing and found on the roof of
the mouth
and on the tongue) as well as hard mouths.
Suction feeders have very protrusible mouths and small teeth.
4) Sense organs
-How does it find its way around?
Many bottom feeders have sense organs, which allow them to
find food in dark or turbid water (barbels, photophores, ampullae of
lorenzini
etc.). Bottom feeding organisms or ones
that live in dark environments may also have small eyes.
The largest eyes are found on active
predators that feed at dawn or dusk, or live in deep water where light
is
limited. Some fish have a lateral line
(often visible) down each side of the body to help sense pressure
changes in
the water. Some fish don’t have true
eyes. How would this help or hinder
them? Would it depend on their
lifestyle?
5) Coloration -How does it hide or blend in to its environment?
A common coloration pattern in fishes is countershading;
this is having a dark dorsal surface (to blend in with the bottom or
dark water
below when viewed from above) and a light ventral surface (to blend in
with the
light water when viewed from below). Pelagic fishes tend to be silvery
or
white, with or without countershading.
Bottom dwelling fish usually have mottled coloration on their
dorsum to
blend in with the substrate, and fish living near vegetation typically
have
vertical bars or other disruptive patterns to allow them to blend into
the
vegetation better. Territorial or inedible (poisonous) fish may be
brightly
colored. Very small fish often tend
to
be clear and nearly invisible to avoid detection. Some
fish (generally deep sea fishes) have
light producing organs (photophores) on their body.
These are thought to attract prey in the
blackness of the deep sea.
6) Protective
Organs -How does it avoid getting eaten?
a) Bony or Hard plates: These are
usually hard enough that a predator
must either be able to bite through the armor in order to hold the
prey, or the
predator must be swift and accurate enough to catch the prey by an
unarmored
portion of the body such as the tail.
Does this tell you something about how or where it might live?
b) Spines or
spine-like rays: Spines increase the “effective size” of the
organism, thus
reducing the number of potential predators.
For example, if I had foot long spines projecting from my chest,
back
and sides, it would make me much more difficult for a lion or polar
bear to
eat. This defense is found most commonly
on slow fish that cannot use speed to elude predators.
Also, some fish have toxins in their spines.
c) Deciduous body
scales: Some fish
have scales that shed easily in flight to
confuse predators and fall off when the organism is bitten, making them
hard to
grasp (e.g. herring have scales that fall off easily)
a) Placiod scales:
These tooth-like scales give some fishes (e.g. sharks) a rough,
protective skin and may serve to improve hydrodynamic efficiency by
reducing
drag. Many skates and rays are not
covered by placoid scales except as patches of bony armor or as spines
b) Ganoid scales:
These are made of ganoine (“enamel”), are rectangular, heavy,
armor-like, and found on ancestral-type fishes such as gars.
c) Body ridge scales:
These teleost scales are of two types
i)
Cycloid scales: These are round,
flat, and thin and are found on more ancestral teleost fishes such as trout and minnows. The
rings (annuli) on these scales can be
used to age some fishes.
ii) Ctenoid scales: These are found on derived teleosts and are
similar to cycloid scales
except that they have tiny comb-like projections (ctenii) on the
posterior
edge. They are thought to improve
hydrodynamic efficiency. These scales can
also be used to age fishes.
8. Fins
a) Pelvic fins:
These are some of the most variable
fins. Fishes with pelvic fins located
far back on the body (abdominal) are usually rover predators that use
them as
stabilizers. In maneuverable deep-bodied
fishes the pelvic fins are below the pectoral fins (thoracic) or in
front of
them (jugular). In some crevice-dwelling
fishes the pelvic fins are reduced or absent and in bottom clingers
they can be
modified into sucking organs.
b) Pectoral fins:
Generally speaking, the higher up on the
body, the more maneuverable the fish.
Also, they tend to be long and pointed on the less active fishes. Fishes that live on the bottom (e.g.
sculpins) may have large, fan-like pectoral fins to help them brace
between
rocks.
c) Dorsal and anal
fins: These are usually long on
roving or deep-bodied fishes to increase swimming stability. Surface- and bottom-feeders often have shorter
dorsal and anal fins.
d) Caudal fin:
The more active the fish is, the deeper the
fork will be in the caudal fin. This
significantly reduces drag, but at the expense of maneuverability and
acceleration.
9. Gill rakers
Go ahead, take a gander at the gill rakers (just be careful
to not break the operculum) Gill rakers serve two functions. They protect the delicate gills from
swallowed objects and also work like a sieve to prevent food particles
in the
buccal cavity from escaping out through the gill openings.
Thus, they can give clues as to the feeding
habits of fishes. Filter-feeding
planktivores have long, fine, closely spaced gill rakers that act as a
sieve or
strainer. Insect-eating and omnivorous
fishes tend to have rakers of moderate length and spacing.
A fish specializing on hard-shelled prey,
such as snails, will have short, stout gill rakers, used to help crush
the
shells.
BIOL 261 Ichthyology - Laboratory Notebook
Family Name:_________________________________
Page
#:________
Common Name:__________________________________
Scale of Drawing: ________________
Identifying Characteristics:________________________________________________________________
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Ecological Notes:________________________________________________________________________
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Example of lab notebook page