by
Garold W. Sneegas
Peering over the gunnel and gazing into the aquatic scenery pasting beneath the keel, is an experience enjoyed by many river explorers. The urge to get an even closer view has led many explorers to leave their ridged craft and enter the water with mask, fins and snorkel. Upon viewing this realm for the first time, an entirely different world opens before you. Patterns of light, bottom contours, plants, invertebrates and schools of fish pop into view that were unnoticed from the surface. You soon realize that viewing the aquatic world from above is like looking into the top of an aquarium; the side view is strikingly different.
In the gin clear, spring-fed rivers of Florida, snorkeling
has been a popular activity for years. While Florida rivers are probably
the most popular, any river system that is clear enough to see a few feet
will have aquatic inhabitants worthy of exploration. As with terrestrial
ecosystems, aquatic ecosystems do not always reveal their secrets easily.
You have to peer into them to get a better understanding of what is truly
going on. Even snorkelers who have made numerous trips down the same river,
may be passing over many small and well-camouflaged inhabitants without
noticing them. Understanding how plants and animals have adapted to the
dynamics of flowing water will help you learn how and where to search
for subjects to view.
Typically rivers with moderate gradients that are easy to navigate by canoe can be good locations for snorkeling. These types of rivers normally have sections of rapids or riffles between pools of calmer water. Calm water sites where canoeist pull over to camp, take breaks, fish or swim, are good sites to start exploring. Begin by entering where the riffles merge into the pool, then drift through the pool to where the next set of riffles begins. You will notice that pools are rarely bowl shaped and smooth bottomed as one might expect. There will often be a number of obstructions such as boulders, gravel bars and tree trunks. In addition the currents rarely flow evenly through the pool. There will be areas of eddies, straight current flow and often calm backwater areas. Plant and animal communities have evolved to take advantage of the varying niches created by moving water and bottom structure.
Underwater view of riffles
After you become familiar with drifting through a pool,
and have a feel for how to maneuver, start taking a closer look. Notice
where the strong currents enter large pools that eddies form off to the
sides. If you swim into the side eddy you will discover you can steadily
position yourself only inches from swift flowing water. From this position
you can observe several aquatic species that only exist in riffle habitats.
When water moves over a rock surface, an area of turbulence is created
on the downstream side of the rock. At these sites, pockets of relatively
calm water form. A large-scale example of this is phenomenon is when a
kayak is steadily positioned in one spot in the middle of raging rapids.
The same phenomenon occurs on a much smaller scale around small rocks
located in any current. Certain types of plants grow only in strong currents,
gaining a foothold by beginning their growth on the downstream edge of
rocks, gravel or submerged trees.
Algae in a strong current
Many invertebrates have adapted to life in and around the rock and gravel areas of strong currents. Some of the more common species encountered are hellgrammites, mayfly and caddisfly larvae. Caddisfly larvae are highly adapted insects that use silk to construct nets and cases. Net-spinning caddisflies construct silk nets facing into strong currents. The nets are constructed with a specific mesh size designed to trap their desired food. The larvae construct a retreat at the base of the net and emerge on a regular basis to feed on the trapped food particles and tend their nets.
Net-spinning caddisfly net
Other species build cases made of sand, gravel or vegetative
material held together with silk. The cases are constructed in an incredible
number of shapes and sizes. The size and shape of the case is a clue to
the identity of the species that constructed the case. One family of caddisflies
constructs cases using very fine grains of sand molded into the exact
shape of a snail shell. The cases mimic a snail shell so closely that
in the 1800's, when this species way first discovered, it was classified
as a new species of snail.
Invertebrates such as mayfly larvae and hellgrammites
(dobsonfly larvae) spend most of their time underneath rocks and in gravel.
They have flat bodies and strong legs giving them a low profile to maneuver
through moving water in search of food. One advantage of living in a current
environment is that food is constantly being delivered to you from upstream.
Invertebrates are very important to the food chain of river ecosystems.
They make up a large part of the diet or many fish species. Many species
invertebrates are also very sensitive to changes in their environment
making them valuable indicators of water quality.
Hellgrammite, Corydalus cornutus
Fishes have also adapted to inhabit riffle areas of streams
and rivers, taking advantaged of the supply of invertebrates as a food
source. Members of the darter family are some of the most colorful and
unique fishes to inhabit riffle areas of streams and rivers. Darters are
small, highly evolved fishes with large pectoral fins, streamlined bodies
and lack an air bladder. These are all adaptations for survival in strong
currents. Sculpins are another fish species found in riffle environments
with a body shape similar to darters. The males of many species of darters
become brilliantly colored in early spring during their spawning periods.
If you are lucky enough to run across spawning darters, you will soon
realize it is an excellent time to view and photograph these fishes. Darters,
and many other fish species preoccupied with spawning, will often ignore
large intruders with funny looking headgear.
Spawning Orangethroat darters, Etheostoma spectabile
As you leave the riffles and move into the pool you will
likely see some type of plant growth. Aquatic plant growth can vary from
small mats of algae to large beds of vascular plants. Close inspection
of plant growth will reveal species of vertebrates and invertebrates that
feed on and live within vegetation. Also, check the surfaces of submerged
rocks, boulders and trees. Fish species such as bass, sunfish, suckers
and trout often congregate in the slack water areas created behind large
obstructions in pools. By positioning themselves in these areas they use
less energy retaining in their desired position. These areas also provide
cover, making them good places to ambush any prey that happens to drift
by. You can also take advantage of this situation by swimming out of the
current and into an area directly behind an obstruction. From this position
you will also have less trouble and use less energy maintaining an observation
position. Once you are in position, remain as still as possible for as
long as you can. The denizens of the pool will eventually become used
to your presence and once they realize you are not a threat, they will
begin to emerge into view from obscure hiding places.
While swimming through a pool, it is often common to see a school of fish scatter and flee in front of you. After you have been in for a while, look behind you and you may find the scattered school swarming around your fins. The fishes are feeding on dislodged invertebrates you have stirred up from the bottom debris. Several fish species are attracted to bottom disturbances caused by larger animals. Sunfish commonly follow aquatic turtles around as they move around and burrow in the bottom.
Longear and Orangespotted sunfish watching the head of a female Spiny softshell turtle, Apalone spinifera
You can take advantage of this behavior to observe and
photograph fish, by acting like a big turtle. To do this position yourself
in one spot and gently start fanning the bottom with one hand while keeping
the rest of your body still. The current will carry debris downstream,
attracting the attention of fishes, which will start moving upstream to
the source of the fanning. If you position a camera with a close-up lens
near the area you are fanning, you will eventually have fish swimming
right in front of your lens. You have to remain still and allow some time
to past for the fish to become accustomed to this huge new "turtle"
stirring up the bottom.
Divers are often only interested large fishes and consider schools of small fishes nothing more than baby fish. A school of small fishes may actually consist of one or more species of mature adults. Many of the smaller species have evolved to take advantage of various conditions in a stream environment. Some members of the minnow family, like the Southern redbelly dace, are strong swimmers and spend a considerable amount of time in strong currents where riffles enter pools. They may also be seen cruising through the open waters pools. Other species, such as Stonerollers, are adapted for bottom feeding and are often seen flashing along the bottom in search of food.
Spawning pair of Central stonerollers, Campostoma anomalum
Members of the Topminnow or Killifish family are fishes
who have evolved for living right at the water surface. They have highly
adapted jaws used for feeding on the surface film. Their diet consists
of tiny animals found on the water surface such as mosquito larvae.
Blackstripe topminnow, Fundulus notatus , with surface reflection
The shallow, calm waters of rivers are areas of interest
worthy of exploration. A common miss perception many people have is that
you need to dive in deep holes to see anything interesting. If you ignore
the shallows you are missing a huge part of the river ecosystem. Shallow
water areas are the preferred spawning sites of many fish species. Sunfish
are probably the most well known because of their numbers and size of
their nests. Male sunfish fan out saucer shaped nest over sand or gravel
bottoms. Several nests may be grouped together at these sites only a few
inches apart. After the spawn, the males’ remains to guard the nests
until the fry have developed enough to fend for themselves. They will
sometimes defend the nests to the point of nipping divers in an effort
to drive them away. This may also include nipping at a camera lens providing
a good opportunity for close-up photography.
Spawning Lonear sunfish, Lepomis megalotis
Fishes have evolved a number of unique spawning techniques.
Some species, such as Stonerollers, dig pits in areas shallow, swift flowing
water over gravel bars. Smaller fishes like the Southern redbelly dace,
will often take advantage of the work done by stonerollers and spawn in
their nests. A number of smaller fishes depend the nests built by larger
species for their spawning sites. Other minnows, like the Rosyface shiner,
rely on massive numbers. Schools of these minnows will congregate near
shallow gravel bars with swift flowing water and on some unknown cue,
the entire school will swam in mass over the gravel and spread their eggs.
Spawning Rosyface shiners, Notropis rubellus
The bluntnose minnow has an unusual and effective, spawning
strategy. Males pick out sites beneath large rocks or submerged vegetation.
They diligently clean off a spot of all silt, algae, debris, etc., on
the underneath side of the rock. A female will move into the site, turn
upside down and attach her eggs to the prepared site. The male remains
at the nest, caring for the eggs and fry by fanning them with his fins
and warding off predators, until the fry are well developed.
Male Bluntnose minnow, Pimephales notatus, guarding eggs
There are other activities you should look for if you
run across spawning activity. Newly spawned eggs are a very attractive
food source for other fishes. Minnows, daters and sunfish, are commonly
seen milling around nests sites. They are waiting for an opportunity to
raid a nest if the guarding male is distracted and moves away from the
nest.
There are many variables that come into play as far as
being able to get close enough to a fish for a good view or photograph.
A few important ones to consider are the species involved, how they react
to divers, time of day or night and the activity the fish is preoccupied
with. During the day some species are so active and skittish around divers
they just about impossible to approach. In many cases if you venture into
the same habitat at night you can easily approach the same species lying
motionless on the bottom. You will also see a number of nocturnal species
that were hidden during the day. Catfish and crayfish are two common species
that emerge to forage at night. Exploring a pool during the day you may
never see a crayfish. If you venture into the same pool at night the bottom
may be crawling with them. If you are exploring a river system of the
Gulf of Mexico or Atlantic coast drainage, an unusual species you may
encounter at night is the American eel. Eels hide during the day under
bottom debris or inside large springs and emerge at night to forage. It
is a little unnerving running into a three-foot eel at night, although
they can bite, they do not have large teeth like saltwater eels and are
not a real threat to humans.
Many species depend on camouflage and cover for survival,
either to ambush prey or to avoid detection from predators. In order to
view these animals you most be patient and look closely. A good example
is a fish called the Hogchoker that inhabits sandy bottoms of Gulf coast
drainage's. Hogchokers are members of the Sole family and they look like
miniature flounders. Hogchokers are an estuary fish that commonly migrates
up freshwater rivers, sometimes over fifty miles inland. They are not
very big, only a few inches long, and can be very difficult to detect
since they bury themselves into sand with just their eyes exposed. What
appears to be barren sand bottom could actually have a large population
of Hogchokers hidden from the casual glance.
Hogchoker, Trinectes maculatus
There are over 790 species of freshwater fishes in North
American waters and thousands of species aquatic plants, invertebrates
and other vertebrates. While the species I have mentioned here may not
be present in the particular river you may choose to explore, other unique
species will be. As your skills and knowledge increase, so will your comfort
level and viewing rewards. Depending on the river system you are exploring
you may need to adapt your skill and equipment level in order to enjoy
the experience. While you can just put on a mask and jump in, learning
a few snorkeling techniques will greatly enhance your comfort level and
ability to explore the underwater world. It is important to have a good
quality mask that fits properly. There are also techniques in swimming
with fins, keeping your mask from fogging up, clearing water from your
mask and snorkel that are important things to learn. If you are diving
in cold waters you will need some type of exposure suit. If there is a
local SCUBA diving shop in your area they can help you select proper fitting
gear. If not there are several books on SCUBA diving that explain snorkeling
techniques.
Once you begin to understand how and what to look for, you will find there are more subjects to learn about, photograph and explore than you thought possible. Do not be fooled by reports from others that there is not much to see in shallow rivers, they may not appreciate or know what they are looking at. Educate yourself and learn from your own experience what there is to see. You may discover a window into a wondrous world beneath the surface.
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