Spring medley

progress of a favorite season

Spring is officially here: the vernal equinox has gone by and the days are rapidly lengthening. There are much livelier signs of spring as well. Sapsuckers have arrived in force, rat-atat-tating on rain gutters and stove pipes (and trees). Juncos trill at the forest edge and song sparrows are tuning up in the brush above the beaches. Pacific wrens sound off from invisible lookouts in the understory. Best of all, ruby-crowned kinglets can be heard, high in the conifers, calling ‘peter-peter-peter’ or singing their full, cheerful song. That’s when spring is really here, for me.

A walk on a favorite beach on Douglas Island was focused on finding mermaids’ purses—the egg cases of long-nosed skates. Every year, about this time, we find them washed up in the wrack at the high tide line—there must be a nursery just offshore. On this day, we found sixteen eggs cases, mostly black, dry, and in various stages of decrepitude. Just a few were still mostly whole and khaki-colored, and two had natural openings at one end, where perhaps the young skate had exited. All the egg cases had sizable holes punched into them. I would love to know if marine predators had nabbed the developing embryos or if the holes were made by a tardy, would-be predator just hoping that an embryo was still inside.

A good find in the rolled mats of rockweed at the high tide line was the body of a sea star, entirely eviscerated. All the gonads and digestive parts had been cleanly removed, neatly exposing the calcareous skeleton of the water-vascular system that runs from the center of the star out into each arm. In a living sea star, the canals of this hydraulic system are filled with fluid, mostly sea water. Numerous branches of the main canal lead to the tube feet (often visible in a live star, in rows under each arm) that function in locomotion and in opening clams. When the tube feet are extended, their ends stick to the rocks or the clam shell, and muscles in the feet contract, pulling the animal forward or pulling the clam shell open. We sometimes see a sea star humped up over a partly open clam while the star is having dinner.

A stroll on the Boy Scout/Crow Point trail led to the goose-flat covered with hundreds of crows fossicking in the dead, brown vegetation. Lots of searching and probing. Sometimes half a dozen crows would suddenly converge on another one, everybody poking at something. Apparently, successful hunts were not very common and the gang thought that sharing was appropriate.

Lots of Canada geese were scattered in small groups on the flats, in the river, and in the vegetation by the river. There were mostly head-down, intent on foraging—grubbing for roots and such, and of course talking to each other. Occasionally, two of them would take off and wing around in a wide circle before landing back where they started. One of these duos took off upstream—perhaps a mated pair about to look for a nest site in the forest.

As we often do, out there, we encountered a fellow we call the Raven Man, who carried a big bag of dog biscuits to feed the ravens. He does this from time to time, and the local ravens recognize him. As he passes through each raven territory, the residents come to greet him and cadge some biscuits. We watched some of these ravens carry five biscuits at a time, first stacking them up in a neat pile so they could be held in the bill. A dog, with some hikers, came along later and sniffed out places where ravens had cached their loot, covering it with grass or moss—surprising the hikers who were not expecting to see dog biscuits in the moss.

Most folks in Juneau are glad to see the snow disappear, at least at the lower elevations. But I loved the good snows we had in February, and here are a few flash-back memories.

–Weasels had been very active in the Peterson Creek meadows and Amalga meadows. They bounded over the clean snow, ranging widely. Every so often, the trail dove straight down under the snow and re-appeared a few feet beyond or disappeared under the overhanging edge of a frozen slough. I think they were hunting voles, whose tunnels run under the snow; did they dive down in response to the sound or fresh smell of vole or were the dives just exploratory? Another treat in one meadow were well-defined trails of mice, showing a good tail-drag.

–On the west side of Mendenhall Lake, one day I found a set of tracks running way out onto the snowy ice and right back again. It was clearly a member of the weasel family, probably a mink. What was it doing??

–A snowshoe trek up a creek out the road was a bonanza of tracks (and no recent human tracks). In the woods on the way up the hill, there were tracks of deer, mouse, weasel, squirrel, and maybe a marten. Big excitement of some large tracks that were surely those of a wolverine—the toes and the gait gave it away. The most fun was seeing a set of wolf tracks coursing over a frozen pond that sparkled with sun-struck hoarfrost.

Now the fun in the snow is finished for the year, and the fun of spring begins. Juneau folks typically love to note the progress of spring, as the season unfolds. Skunk cabbage emerging, pussy willows appearing, blueberry buds expanding, the gradual arrival of more kinds of birds, ravens carrying sticks for a nest—they all mark the progress of a favorite season.

Mermaids’ purses

…and their cartilaginous currency

alaska-skate-egg-case-by-gerald-hoff-afsc
Photo by Gerald Hoff, Alaska Fisheries Science Center

This is a fanciful name for the egg cases of skates, which are cartilaginous fishes related to rays and, more distantly, to sharks. When some friends found a few of these egg cases on North Douglas beaches, I got interested in learning more about them. Not being a marine biologist, I had to do a bit of digging, but I got a start with the help of a genial skate biologist at NOAA. Here are some of the things I think I have learned.

Skates put their eggs into tough, leathery cases. The cases are deposited in traditional nursery sites that are used year after year. According to the skate biologist, there are two skate species in our area that use relatively shallow-water nurseries and are the most likely ones whose egg cases occasionally appear on our beaches. These two are the big skate and the longnose skate. Beachcombers should be able to distinguish the egg cases of these two species quite easily: Egg cases of big skates are typically more than eight inches long with short stubby horns at the four corners; those of the longnose skate are about four inches long, with slender horns. When the cases are laid, they often bear tufts of sticky threads that help stick the case to the seafloor; these threads may get worn off on cases that wash up on beaches. Most egg cases that show up on beaches are empty; the young skates are gone.

Most skates, including the longnose, put only one egg in each case, but the big skate may have as many as seven or so in each case. There is little available information on how many egg cases a female skate produces each year, but it is only a few hundred at most or, in some instances, much less. The growing embryos are well endowed with abundant yolk and the cases require considerable material and energy to make; this large parental investment per embryo means that the number of embryos must be fairly small. The case stays closed for several weeks, and then slits open in the horns, letting in sea water and oxygen; the embryo develops a temporary filament on the tail, and this undulates in one of the horns to facilitate the movement of water in and out. The eggs incubate in their cases for a long time, averaging about nine months for the big skate (but some other skates living in very cold water, such as the Bering Sea, may have incubation periods of several years!).

Predatory snails can bore into the cases and eat the contents; in some situations, over 40% of egg cases have been depredated by snails. In the Bering Sea, the intensity of predation was lower in nurseries with high densities of egg cases, suggesting that there is some safety in numbers—(this is referred to as predator satiation, or predator swamping, or the selfish herd effect). After the lengthy incubation, when the eggs finally hatch, the ‘pups’ are miniature versions of their parents. They have many predators, and juvenile survival is undoubtedly very low.

Both big skates and longnose skates can, but apparently seldom do, live for more than about twenty years. Big skates in the Gulf of Alaska were estimated to mature at about five to nine years of age, longnose skate at age nine to twelve years. Females mature somewhat later in life than males, particularly in big skates.

Skates eat a variety of fishes and invertebrates, including crabs, octopus and squid, and worms.

alaska-skate-by-alaska-fisheries-science-center
Photo by Alaska Fisheries Science Center

Around the world, some skate populations have crashed dramatically, due to overharvesting plus numerous by-catch captures in fisheries directed at other species; by-catch captures are just discarded. Both big skates and longnose skates in Alaska are increasingly subject to both directed harvest and by-catch mortality, and fisheries biologists report declining numbers of these species. Therefore there is both management and conservation concern for these species.

The North Pacific Fishery Management Council recently identified six skate nursery areas in the Bering Sea as Habitat Areas of Particular Concern. These areas are not closed to fishing but will be monitored for changes in skate egg density and other factors. Consultation will be needed for proposed activities that might modify habitat or otherwise impair skate reproduction, such as drilling or laying of cable in these areas. There was no report of any quasi-protective measures for the Gulf of Alaska.

All you beach-walkers, take note: if you find a skate egg case in your peregrinations, please send a good digital photograph of it, with precise location information, to jerry.hoff@noaa.gov. He is keeping records in a database and will identify the egg cases you find.