Salmon

What species would travel over 2000 miles just to have young and then die? It
has been said that anyone who has not seen a wild salmon has not seen what a
fish should be. Salmon was the common name applied to fish characterized by an
elongated body covered with small, rounded scales and a fleshy fin between the
dorsal fin and tail. In this paper I will be discussing history of studying
salmon, the life cycle, spawning and mating behaviors; which has much to do with
the total reproduction of salmon. Salmon were studied earlier than some may
think. Experiments were done by men that date back to the mid-1600s. These
experiments involved catching salmon in fresh water, tagging them, and then
catching them again when they return to the same place, around six months later.

These experiments were doubtful and it was not until the beginning of the

1900’s that proof was available that the salmon returned home. (Shearer)

Although usually drab in color before the breeding season, which varies with the
species, members of the salmon family develop bright hues at spawning time. The
male, during this mating season, usually develops a hooked snout and a humped
back. "In many diverse taxa, males of the same species often exhibit
multiple mating strategies. One well-documented alternative male reproductive
pattern is \'female mimicry,\' whereby males assume a female-like morphology or
mimic female behavior patterns. In some species males mimic both female
morphology and behavior. We report here female mimicry in a reptile, the
red-sided garter snake (Thamnophis sirtalis parietalis). This form of mimicry is
unique in that it is expressed as a physiological feminization. Courting male
red-sided garter snakes detect a female-specific pheromone and normally avoid
courting other males. However, a small proportion of males release a pheromone
that attracts other males, as though they were females. In the field, mating
aggregations of 5-17 males were observed formed around these individual
attractive males, which we have termed \'she-males.\' In competitive mating
trials, she-males mated with females significantly more often than did normal
males, demonstrating not only reproductive competence but also a possible
selective advantage to males with this female-like pheromone." In the
competitive mating trials, the she-males were successful in 29 out of 42 trials.

The normal males won out in only 13! The authors ask the question: Why aren\'t
all males she-males given such an advantage? (Mason, Robert T., and Crews,

David; "Female Mimicry in Garter Snakes," Nature, 316:59, 1985.)

Comment. Among the fishes, bluegills and salmon (and probably many others) have
female-appearing males competing with normal males. Abstract: The influence of
sperm competition and individual mating behaviour in an externally fertilizing
species of fish, the Atlantic salmon (Salmo salar), is estimated from video
observations of multiple-male spawnings and subsequent paternity analyses. One
male dominated the paternity during polygamous spawnings, fathering more than

80% of the progeny in a single nest. Behavioural analyses of the spawnings
showed that the first-mating male had sperm precedence in 6 out of 10 cases. In
three of the other spawnings, sperm limitation likely influenced individual
success, as the first-mating male had participated in a large number of
spawnings. In the final, nearly simultaneous spawning, male size was more
important than the 0.6-s difference in spawning times. Thus, male fertilization
success can be influenced by a variety of factors, including sperm precedence,
male size, and spawning history. Back to Table of Contents Before mating, one
parent excavates a nest for the eggs; after the eggs are deposited and
fertilized, the female stirs up the stream bottom so that earth and stones cover
the eggs and protect them. The eggs hatch in two weeks to six months, depending
on the species and the water temperature. During the migrations and
nest-building activity that precede mating, neither the females nor the males
consume food. In the life cycle of the pacific salmon, nature recycles the
parents to feed the babies. Mature salmon leave the Pacific Ocean as saltwater
fish, never again to eat as they battle their way up the Columbia River to spawn
in the home stream where they were born. Those born in the upper reaches of the

Columbia River\'s tributary stream, the Snake River, travel more than 1,000 miles
inland to lay their eggs and fertilize them, roughly one fourth of the distance
across the United States. Without enough reserves in their bodies to get back to
the Pacific, the adult salmon spawn and die. To spawn, a female salmon scoops a
nest in stream-bottom gravel by waving her tail and deposits her eggs in the
hole. The male releases milt (sperm) into the water that covers the