Fish Biology & Physiology Flashcards

What term describes the bright or distinctive colors many fish develop during spawning season to attract mates?

Answer: Nuptial coloration

Nuptial coloration refers to the striking breeding colors (typically in males) that appear during spawning season to attract mates and signal reproductive fitness, as seen in male brook trout and sockeye salmon.

Which hormone class plays the primary role in triggering smoltification in juvenile Pacific salmon?

Answer: Thyroid hormones (thyroxine)

Thyroid hormones, particularly thyroxine (T4), are the primary drivers of smoltification, stimulating the broad physiological changes in gill ion-transport capacity, body morphology, and migratory behavior needed for seawater life.

What is the migratory life history pattern of catadromous fish such as American eels?

Answer: Born in the ocean, migrate to freshwater to grow, return to the ocean to spawn

Catadromous fish like the American eel are born in the ocean (Sargasso Sea), migrate to freshwater rivers and lakes to grow for many years, then return to the ocean as adults to spawn and die.

What type of muscle tissue comprises the majority of body mass in most fish and powers burst swimming?

Answer: White glycolytic (fast-twitch) muscle

White (fast-twitch, glycolytic) muscle constitutes the bulk of fish body mass and generates the powerful, rapid contractions needed for burst swimming during prey capture and predator escape.

How do most cartilaginous fish (sharks and rays) achieve buoyancy in the absence of a swim bladder?

Answer: By storing large quantities of low-density squalene oil in an enlarged liver

Cartilaginous fish lack a swim bladder and instead have a very large liver containing squalene and other low-density lipids that provide positive lift and reduce the animal's overall density toward neutral buoyancy.

What is the cloaca in fish anatomy?

Answer: A common posterior chamber and opening for the digestive, urinary, and reproductive tracts

The cloaca is a single posterior opening found in cartilaginous fishes and some basal bony fishes where the intestinal, urinary, and reproductive ducts converge into a shared exit chamber.

Which reproductive strategy involves a male fish fertilizing eggs laid by multiple females in a single nest and then guarding the nest?

Answer: Polygyny with paternal care

Polygyny with paternal care — seen in species like largemouth bass and bluegill — involves a territorial male that fertilizes eggs from multiple females deposited in his nest and then guards the eggs and fry until they disperse.