Freshwater Fishes

Aquatic Ecology

Fishes Diversity

• Most species-rich group of vertebrates, >24,000

• All other vertebrates approximately 23,500 (Table 5.1, p.124)

• 3 Classes:– Agnatha– Chondrichthyes– Osteichthyes

• Bony Fishes = Teleosts

Why are there so many FW fish species?

productivity: freshwater habitats are generally more productive than marine environments– shallower more sunlight ⇒ ⇒

more photosynthesis– more terrestrial input of

nutrients• isolation: FW habitats tend to

be isolated by:– drainages, drought, landslides,– waterfalls, plate tectonics, etc.

⇒ impedes gene flow ⇒ can lead to explosive speciation when new habitats are invaded

• in contrast, marine habitats are more connected, separated mainly by continents)

Cause of high rate of speciation in FW: rapid evolution

Evolution: a change in gene frequencies between generations Causes of evolution:

1. Natural selection: best adapted individuals pass on more genes to the next generation than do less adapted individuals

2. Genetic drift: random processes cause certain genes to disappear from or become fixed in a population

3. Gene flow: genes enter a population from outside sources4. Sexual selection: selected genes become more common in the

next generation when one or both sexes (1) prefer to mate with individuals with certain phenotypes that (2) have a genetic basisBUT…

• speciation will only occur if evolving populations become reproductively isolated

Causes of reproductive isolation

1. Physical (geographic) isolation: populations cannot come into contact due to physical barriers

2. Environmental isolation: populations live in different habitats

3. Behavioral isolation: mating behaviors of individuals from different populations are too different for successful reproduction

4. Mechanical isolation: sex organs are too different formating to occur

5. Physiological isolation: hybrid offspring are not formed or have lower fitness than pure offspring

River Monsters

Types of Fishes in Freshwater• Primary FW fishes: families strictly confined to FW, cannot tolerate

SW; have a long evolutionary history in FW- e.g., characins, minnows, catfishes, sunfishes

• Secondary FW fishes: families generally restricted to FW but may occasionally tolerate SW; originally of marine origin

- e.g., cichlids, poecilids• Freshwater representatives of marine families (“peripheral”)

- e.g., sculpins, puffers, gobies, stingrays• • Diadromous fishes (“peripheral”): migrate from SW to FW or

vice versa at different stages in their life cycles- e.g. salmon, smelt, eels

• Euryhaline marine visitors– e.g., sharks, snappers

Orders to Research

1. Clupeiformes – Herring (shad)

2. Cypriniformes – Minnows (carp, dace, koi)

3. Esociformes – Pike (pickerel, mudminnows)

4. Perciformes – Perch (bass, darters, walleye, sunfish, drums)

5. Salmoniformes – Salmon (trout, whitefish)

6. Siluriformes – Catfish

7. Cyprinodontiformes – Mosquitofish (guppies)

Order Perciformes

• Perciformes is not only the largest order of fish, but also the largest order of all vertebrates.

• There are 9,293 species, which is more than one third of all the fish species in the world.

• Most members of this order are marine fish, but about 2,000 species are freshwater.

• Many species of marine fish do spend part of their life cycle in freshwater

• (Temperate Basses, Sunfish, Perches, Drums)

Centrarchidae Genus Level Identifiers

• Genus Ambloplites(rock basses)- Typical bright sunfish coloration absent. Sometimes called "redeye" due to distinctive red iris. Lower jaw projecting. Dorsal fin with 10 or 11 spines. Anal fin with 5 or more spines and 11 or fewer soft rays.

• Genus Centrarchus (flier)- A single species exists within this genus. Dorsal fin with 12-13 spines. Anal fin with 7 or 8 spines and 14 or more soft rays.

• Genus Enneacanthus(sunfish)- Caudel fin slightly rounded. Dorsal fin with 8 or 9 spines. Anal fin with 3 spines.

• Genus Lepomis (sunfish)- Often brightly colored, especially \ during the breeding season (see fig. 2). Dorsal fin with 9 to 12 spines and 10-12 rays. Anal fin with 3 spines.

• Genus Micropterus (black basses)- Body elongate. Distinctive notch between spinous and soft dorsal fin. Dorsal fin with usually 10 spines and 10-15 rays. Anal fin with 3 spines.

• Genus Pomoxis (crappies)- Body deep and compressed. Dorsal fin with 5 to 8 spines and 14-16 rays. Anal fin with 5-7 spines.

• PHOTO LIBRABRY OF SUNFISHES

Tips on Identifying Percidae• Genus Etheostoma (darters)- 1-2 anal fin spines. Body variable,

although not as elongate as Ammocrypta. Caudal fin emarginate, rounded, or truncate. Males often very colorful. Most species are sexually dimorphic (either pattern and/or color).

• Genus Perca (yellow perch)- 2 distinctive anal fin spines. Forked caudal fin. Overall body size much larger than darter taxa. Color bronze or yellowish with dark saddles fading ventrally.

• Genus Percina (darters)- 2 anal fin spines. Adults often larger and more robust than Ammocrypta. Generally elongate, but not as thin as Ammocrypta.

• Genus Sander (sauger and walleye)- 2 poorly developed anal fin spines. Caudal fin forked. Bright coloration absent. Body size the largest of the perch genera.

• PHOTO LIBRARY OF PERCHES

Perca flavescens

Order Esociformes

• There are two families in this small order, both of which occur in North America.

• These freshwater fishes have elongate to relatively elongate bodies, with the dorsal and anals fins located far back on the body.

• They lack adipose fins, and breeding males do not have tubercles. (National Audubon Society Field Guide to North American Fishes)

• (Pikes and Pickerels)

Tips for Identifying Pickerel• Esox americanus americanus (redfin

pickerel)- Snout is convex and short. Cheek and opercle fully scaled.

• Esox americanus vermiculatus (grass pickerel)- Snout is concave and longer than that of the redfin pickerel. Cheek and opercle fully scaled.

• Esox lucius (northern pike)- Cheek fully scaled, opercle partially scaled. Pattern and coloration slightly different than the pickerel, although this may be difficult to distinguish in younger individuals.

• Esox masquinongy (muskellunge)- Cheek and opercle partially scaled.

• Esox niger (chain pickerel)- Very similiar to grass pickerel. Cheek and opercle fully scaled. Individuals longer than 19 inches often have distinct chain-like reticulations.

Chain Pickerel: Esox niger

Order Cypriniformes

• This order of fish has 2,662 species, with the greatest diversity of species found in Southeastern Asia.

• All the fish in this order lack teeth in their mouths.

• Many species are used for food, aquarium fish, or research.

• Some common examples are the goldfish, minnows, and loaches

• (Minnows, Carps and Suckers)

Common Genus of Minnows• Genus Campostoma (stonerollers)- Body elongate and moderately robust. Unique adaption of

hardened tissue on lower jaw (used to scrape algae). Breeding males often have striking tubercules.

• Genus Clinostomus (daces)- Body moderately deep and moderately compressed. Mouth terminal. Males (less distinct in females) often have a thick red lateral stripe (especially when breeding).

• Genus Cyprinella (shiners)- Body elongate to moderately deep. Dorsal fin insertion just posterior of posterior end of pelvic fin insertion. Dorsal fin with varying degrees of dark pigmentation.

• Genus Cyprinus (common carp)- Body deep and large when fully mature. Distinct barbels present near mouth. Dorsal fin somewhat stiffer than other cyprinids.

• Genus Erimystax (chubs)- Body elongate. Mouth subterminal. Dorsal fin anterior insertion point anterior of pelvic fin. Breeding males without bright colors.

• Genus Luxilus (shiners)- Body elongate to deep, often compressed. Mouth terminal to somewhat oblique. Dorsal fin anterior insertion in line, or slighly behind pelvic fin anterior insertion point.

• Genus Lynthrurus (shiners)- Body elongate to deep, compressed. Mouth terminal to moderately oblique.

• Genus Nocomis (chubs)- Body robust, slightly to moderately deep. Mature adults larger than most cyprinids. Eye small in relation to size of body. Body often dark dorsally, becoming lighter ventrally.

• Genus Notropis (chubs, minnows, and shiners)- A very large genus that does not have consistent, defining characteristics.

• Genus Pimephales (minnows)-Body robust (especially in adults), slightly to moderately deep. Mouth subterminal, terminal or slightly oblique. Snout ends abruptly, somewhat rounded. No bright colors, although dark blotches of breeding fatheads (Pimephales promelas) can be quite striking.

• Genus Semotilus (chubs)- Body robust. Adults may grow quite large under the right conditions. Mouth terminal or slightly oblique, quite large.

Golden Shiner (Notemigonus crysoleucas)

Creek Chubsucker

Order Siluriformes

• This large order contains 34 families, but in the US there are only 2 native families with most belonging to the Ictaluridae.

• North American catfishes are closely related to the Cypriniformes because both groups have an organ connecting the swim bladder with the inner ear, providing excellent hearing.

• The Ictaluridae have four pairs of barbels, an adipose fin, and each dorsal and pectoral fin has a single spine. (National Audubon Society Field Guide to North American Fishes)

• (North American Catfishes)

Common Genus of Catfishes

• Genus Ameiurus (bullheads, white catfish)- Caudal fin rounded, emarginate or slightly to moderately forked. Usually 6 dorsal rays. Usually 8 pelvic rays. Adipose fin not connected to caudal fin.

• Genus Ictalurus (catfish)- Caudal fin moderately to deeply forked. Usually 6 dorsal rays. Usually 8 pelvic rays. Adipose fin not connected to caudal fin.

• Genus Noturus (madtoms)- Caudal fin rounded or truncate. Usually 9 pelvic rays. Adipose fin connected to caudal fin, or very nearly so.

• Genus Pylodictis (flathead)- Caudal fin slightly rounded, truncate or slightly emarginate. Flat and large head. Lower jaw projecting. Adipose fin not connected to caudal fin.

Tadpole MadtomBrown Bullhead

Order Salmoniformes

• This order contains 2 families, both of which are found in North America.

• Smelts (Osmeridae) and Trouts and Salmons (Salmonidae).

• They include freshwater, marine, anadromous, and deep-sea species.

• All have soft-rayed fins, adipose fins, and abdominal pelvic fins. (National Audubon Society Field Guide to North American Fishes)

• (Trout and Salmon)

Atlantic Salmon (Salmo salar)

Brook Trout (Salvelinus fontinalis)

Ecology of Fishes: Habitat & Distribution

• Physical factors affecting distributions:

• temperature

• light (turbidity)

• gradient (steepness)

• substrate

• flow regime

• size of water body

Chemical factors:

• pH

• dissolved oxygen

• salinity

• dissolved ions

• anthropogenic pollutants

Biological factors:

• predator-prey interactions

• competitive interactions

• symbiotic interactions

Freshwater Habitats:

• streams

• rivers

• puddles

• ponds

• lakes

• hot (& cold) springs

• caves

Physical and chemical factors:Zonation of Temperate Streams

• Zones

• erosional

• intermediate

• depositional

• Fishes tend to occur in areas with particular physical and chemical characteristics

1. Erosional zone• physical characteristics:

high gradient, rocky bottom, swift current, cold water; long riffles and small pools are main habitat

• typical fishes: streamlined, active swimmers (i.e.,trout), small bottom-dwellers (sculpins and dace)

2. Intermediate zone

• physical characteristics: moderate gradients, warm water, intermediate current; main habitats are shallow riffles and deep pools with rocky bottoms or mud bottoms, and runs with undercut banks

• typical fishes: minnows, suckers, sunfishes, darters, catfishes

3. Depositional zones

• physical characteristics: lower reaches of rivers, where waters are warm, turbid, and slow flowing and stream bottom is generally muddy; aquatic plants can be common

• typical fishes: deep-bodied forms that are bottom feeders (carp, suckers), planktivores (shads), invertivores (sunfish), or predators (centrarchid basses). (Same as those found in nearby lakes)

Water Monitoring and Standards

• NJ DEP – Fish IBI (Index of Biotic Integrity)

• Intro to IBI