Homewaters by David B. Williams;

Author:David B. Williams;
Language: eng
Format: epub
Publisher: Lightning Source Inc. (Tier 3)
Published: 2021-01-15T00:00:00+00:00

8

Old Fish and New Laws

If salmon are the most iconic fish of Puget Sound and herring the most central to the ecosystem, rockfish are the most quintessential resident, with more species, more habitats, and a more direct connection to the Sound’s geology than any other fish. Of the 253 fish species in greater Puget Sound, slightly more than 10 percent are rockfish. The genus— the aptly named Sebastes, meaning magnificent—includes twenty-seven species.1 The next largest genus, Oncorhynchus (salmon), includes a mere seven species. Rockfish win on style points, too. One rockfish species bears a yellow swoosh on a yellow-freckled, blue-black body; another has dark vertical stripes set against a pinkish background; and a third sports fluorescent orange blotches that seem to glow from within. As Shawn Larson, curator of Conservation Research at the Seattle Aquarium, told me: “We have salmon, but rockfish are more interesting. They are what make the Sound colorful underwater.”2

With their rich diversity in size, food preference, and life history, rockfish have been able to spread across and take advantage of the full range of Puget Sound’s glacially influenced topography. From the lightfilled surface down to the darkest depths, from sandy eelgrass flats to rocky reef kelp forests, above old wrecks and under fishing docks, these multihued fish have filled nearly every niche, natural or artificial, in the waterway.

The great taxonomic variety of Sebastes stems primarily from their means of reproduction. Unlike most marine fishes, in which males and females broadcast their sperm and eggs and simply hope for the best—a process marine biologists sometimes refer to as “spray and pray”—rockfish have sex. Their mating, a sort of dance, shudder, and penetration, results in fertilized eggs that develop into embryos within the female fish, which are released, or extruded, as larvae about half the length of a grain of rice. The number of larvae depends on the species: the bigger the better. A female of the checkbook-sized, Puget Sound rockfish species extrudes about 3,330 larvae, compared with up to 3,000,000 for the three-foot-long, twenty-five-pound yelloweyes. The biggest and longestlived species can keep procreating for decades, annually cranking out millions of live young, which eat anything they can fit into their tiny mouths. As happens with most fish, a vanishingly small number reach adulthood, but it’s hard not to admire rockfish productivity. When it fails, though there can be dire consequences.

From an evolutionary perspective, reproducing through copulation instead of group spawning means that when a physical or physiological variation arises, a female may choose to mate only with a male that possesses that trait, which facilitates passing it along to the next generation, who now have the potential to evolve into a new species.3 Combine sex with high fecundity and diverse and dynamic habitats, such as those found all along the West Coast and in Puget Sound, and you have a perfect recipe for evolving a range of magnificent species.

Another factor influencing rockfish evolution is the series of underwater sills in Puget Sound. Researchers hypothesize, for example, that soon after glacial retreat, some unknown number of brown rockfish colonized Puget Sound.

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