Alewife

Clupeidae

• scales on keel
•  dorsal fin origin ahead of pelvic fin origin

Gizzard shad

Clupeidae

• dorsal fin origin behind pelvic fin origin
• elongated ray of dorsal fin

White sucker

Catostomidae

• lips are very bumpy

Northern hog sucker

Catostomidae

• concave head
• blotchiness on scales
• angled head

Shorthead redhorse

Catostomidae

• large scales
• no indent on mouth
• not concave dorsal

Golden redhorse

Catostomidae

• large scales
• V-shaped indent of mouth
• concave dorsal

Rainbow trout

Salmonidae - Salmonidae

• many black spots
• tail spots
• dorsal fin heavily spotted
• evenly spread spots on tail fin
• pretty colorful

Brook trout

Salmonidae - Salmonidae

• weakly forked tail
• red spots w/ blue halo on body
• spots on caudal fin
• red anal fin w/ black and white stripe

Lake trout

Salmonidae - Salmonidae

• tail strongly forked
• no stripes on fins
• light spots on dark background

Brown trout

Salmonidae - Salmonidae

• few to many spots that are ovals
• adipose fin has red edge
• tail not really forked
• spots are red w/o halo
• no red color on anal fin

Chinook salmon

Salmonidae - Salmonidae

• spots on upper half of sides
• tail spots
• tail forked
• sharp teeth
• lines down body

Cisco (lake herring)

Salmonidae - Coregonidae

• deep body
• adipose fin
• origin of pelvic fin well behind pectoral fin

Lake whitefish

Salmonidae -  Coregonidae

• no jaw teeth, subterminal mouth
• round belly on front
• silvery sheen

Northern pike

Esocidae

• 5 pores
• 14-16 branchiostegal rays

Grass pickerel

Esocidae

• rounded forked tail
• 4 pores
• 12 branchiostegal rays

Yellow bullhead

Ictaluridae

• adipose fin
• yellow chin barbels
• 24-27 anal rays

Black bullhead

 Ictaluridae

• adipose fin
• bar at base of tail
• even color 
• 15-21 anal rays

Brown bullhead

Ictaluridae

• adipose fin
• mottled
• saw-like barbs
• 21-24 anal rays

Channel catfish

Ictaluridae

• deeply forked tail

Central mudminnow

Umbridae

• homocercal tail
• dorsal fin far back
• lip connected to snout

Rainbow smelt

Osmeridae

•  adipose fin
• prominent jaw teeth
• elongated body

Trout perch

Percopsidae

•  spines on dorsal, anal, and pelvic fin
• big head, big eye, big mouth
• adipose fin
• forked tail

Pirate perch

Aphredoderidae

• homocercal tail
• "migrating anus"
• big dorsal

Burbot

Lotidae

• single chin barbel
• long continuous anal and dorsal fin
• homocercal tail
  

Blackstripe topminnow

Fundulidae

• vertical bars on flank
• superior mouth

Brook silverside

Atherinidae

• spots on back
• big eye
• beak-like snout

Threespine stickleback

Gasterosteidae

• 3 spines 
  

Ninespine stickleback

Gasterosteidae

• 9 spines

Brook stickleback

Gasterosteidae

• discoloration
• 5 spines

White bass

Moronidae

• striping not offset
• gap between dorsals

Yellow bass

Moronidae

• broken and offset striping
• connected dorsals 

Freshwater drum

Sciaenidae

• elongated ray on pelvic fin
• curved lateral line

Round goby

Gobiidae

•  dark spot on 1st dorsal fin
• fused pelvic fins