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Fins and Fish Scales

Fins and Fish Scales
Ranger Steve

By Ranger Steve Mueller

I wonder how often fish-eating birds experience a bloody digestive tract when eating. If a fish spine has not drawn blood on your hand, you likely have not fished. I am a bit clumsy with my hands but other anglers I know have given blood to a fish. 

I have watched a Belted Kingfisher catch a small fish, carry it to a tree branch and spend several minutes beating it against the branch. I have wondered why. Perhaps the kingfisher is making sure it is dead so when swallowed, a wiggling fish does not pierce its innards with a sharp fin ray. Great Blue Herons carefully manipulate prey so they are swallowed headfirst. This makes the fins lay flat so they do not poke their esophagus in route to the stomach. 

Note the various fins on the rainbow trout. Photo in the public domain.

Scales and thin skin function to protect the fish from injury and infection much like our skin protects us. Scales are attached to the body from the headend and point backwards. The orientation allows water to flow easily with little friction or resistance. In addition to scale protection, fish are covered with a slippery slime that protects them from bacterial and other infections.

Scales are a beautiful sight that most of us miss. In a recent article I mentioned carrying a hand lens in my pocket to use when wanting a close look at small objects. Using a magnifying lens allows examination of different types of scale shapes, sizes, and colors. I seldom concentrate on those fascinating features. I am most interested in fish age compared to size. Scales, like tree growth rings, indicate approximate age. During the warm growing season, a fish adds a ring but two could be added if seasonal growth is interrupted for some reason. 

A reason anglers have been poked by fin rays is because the slime makes a fish difficult to hold. Bravo for the skill of fish-eating birds holding them. Birds like osprey capture fish with talons instead of their beaks like is done by birds in the heron family. 

In addition to sharing thanks and remembrance for others on Memorial Day, we venture with family and friends to lakes and streams to fish for food, fun, friendship, and to find solace and inspiration among nature niches.

It was not fish that interested me most. The early morning calm lake surface that changes to ripples or even waves holds my attention. Views into the depths where plants anchor themselves are of interest not only to me but fish. A favorite fishing lake had a river enter from the north and exit to the south. We would take our rowboat into the river to explore favorite hiding places where fish waited to dart after passing prey. If we cast and handled our lures properly, we enjoyed a good struggle for a coming meal. Often fish measured under the size limit but that was fine with me. I prefer to release most.

When taking a fish off the hook, I examine the membranous fins that have hard and soft spines. On the back are dorsal fins. The front one has hard spines and the rear ones are soft. The presence and character of each varies among types of fish. Along the body line are other unpaired single fins called the tail or caudal fin and anal fin.

Paired fins on the sides of the body are called pectoral and pelvic. The pectoral are behind the gill cover opercula. One can watch the opercula pulsate in and out as water is taken in through the mouth, passed over the gills, and released. Pelvic fins are in the lower rear area of the body. A special type fin, called the adipose fin, is present in trout and some others. It is small, soft, and spineless in front of the tail on the upper back. 

When fishing and waiting for a panfish to strike, examine the fins and scales of bass, pike, trout, and panfish in your catch with a hand lens. I am not a patient angler so I fish for larger game fish where I keep casting and reeling in my chosen lure. Watching a bobber is great for many but not me. Time in a boat allows more than surface ripple watching. We enjoy the shoreline contour, trees, clouds, and movement in the sky. Sounds abound to let us know we are alive. Do not miss the surrounding wonder. That is the reason for being outdoors. 

Natural history questions or topic suggestions can be directed to Ranger Steve (Mueller) at odybrook@chartermi.net – Ody Brook Nature Sanctuary, 13010 Northland Dr. Cedar Springs, MI 49319 or call 616-696-1753.

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Ray Winnie
Kent County Credit Union


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