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Fish Bulletin No. 3. The Spawning of the Grunion (Leuresthes tenuis)

  • Author(s): Thompson, Will F
  • Thompson, Julia Bell
  • et al.
Abstract

On moonlit nights during the high tides of March, April, May and June, a small smelt comes in on the long sandy beaches of California. It comes in with the sweep of the water up the beach as the waves break, and lies for a moment glittering in the faint light, then squirms and flops back into the wash of the next wave. Along the whole magnificent sweep of broad sandy shore at Long Beach, crowds of people gather to pick up these fish, by the light of the moon, and of bonfires, and of flashlights. Some content themselves with picking up the stranded fish; others utilize wire screens, or even portions of beach seines, catching the smelt as they venture inshore. The fish they obtain are less than the length of one's hand, slender, with a broad lateral stripe, and very plainly of the smelt family. At Long Beach no name other than "grunion" is ever heard, although one gleans from scientific works such names as "silversides" and "little-smelt." Those who gather this "grunion" know that it comes in to spawn its eggs, but of the marvelous story that lies ready to discovery, they know not a whit. The crowds of bathers who follow in their footsteps on succeeding days, little think that four inches below their feet is unfolding one of the really remarkable stories in the annals of natural history. Surely the grunion has a purpose in thus venturing out of its native element, to lay its eggs in the sand. In some way the act must serve the species, must aid it in its survival. It must escape its enemies, or obtain favorable conditions for development. Other smelts lay their eggs very differently, attached to the rocks or the bottom of the ocean by slender stalks or filaments. Many species migrate into brackish or even fresh water to spawn, while other genera or species are entirely confined to fresh water. Even in species apparently closely related, the spawning habits have become diverse, perhaps under the pressure of the struggle for survival. Fish, smelts and others, lay their eggs in every conceivable marine locality where suitable conditions may be obtained, but it remains for the "grunion" to utilize what is practically dry land. For that is actually what it is doing when it ventures inshore as far as the high tides will carry it. The eggs are laid in the sand as far down as the fish is able to bury them, and far above the level of the average tide. The way in which it does this, the history of the eggs in the sand, and the story of their escape are interest-compelling.

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