The Japanese spider crab, (Macrocheira kaempferi), is a very leggy deep-sea arthropod, and it’s the largest known arthropod. The Japanese spider crab shown—nicknamed Crabzilla—measures “10ft from claw to claw – is still growing, and could live until it is 100.” According to the Daily Mail, Crabzilla will be “display[ed] at the National Sea Life Centre in Birmingham.”
Image by Greg Skomal via Flickr and Dot Earth Blog
Two great white sharks (Carcharodon carcharias) were recently tagged off the Massachusetts coast by Division of Marine Fisheries biologist Greg Skomal and fisherman Bill Chaprales. In the western Atlantic Ocean, great white sharks are found from “Newfoundland, Canada to Argentina,” so finding great white sharks in Massachusetts’s waters isn’t unusual.
Furthermore, dramatic sightings of great white sharks aren’t unknown to the Bay State. In 2004, a female great white was found swimming in a shallow salt pond on Naushon Island (see images and videos of the magnificent beast below).
Great white sharks are a cosmopolitan species, so they’re not restricted to the Atlantic Ocean. For instance, a female great white that was tagged in South Africa “completed the first known transoceanic trip for an individual shark, traveling farther than any other shark known, more than 12,400 miles (more than 20,000 kilometers) to the coast of Australia and back again . . . in just under nine months, the fastest return migration of any swimming marine organism known.” Consequently, despite being well known in popular culture, there are still a lot of unknowns associated with great white sharks, so tagging these sharks is important to yield much needed data on the species.
The recent Massachusetts shark sightings has “prompted a swimming ban for the rest of the Labor Day weekend at some oceanside beaches in Massachusetts.” Earlier in August, “two kayakers reported that they saw what they believe was a great white shark attacking a seal off Chatham over the weekend, saying they observed a large black fin slicing through the water near a seal in distress.” More on the most recent great white shark sightings from the Boston Globe:
A local harpooner working with a state biologist placed electronic tags on two great white sharks today off the coast of Chatham.
“He did it in one shot,” said state biologist Greg Skomal, referring to harpooner Bill Chaprales, a fisherman from Marstons Mills who tagged the sharks. “We don’t swing the bat unless it’s a strike.”
The tags, which will use satellite-based technology to record the sharks’ travels, should give scientists information to help them better understand their migratory patterns.
Skomal and his team set out to identify the species of five sharks reported off the waters of Monomy Island Thursday and determined that at least one was a great white shark then. Today, they identified two more great white sharks.
Skomal, who heads the Division of Marine Fisheries shark research program, said Chaprales tagged the first great white around 9 a.m. near the southern tip of Monomoy Island and the second about a mile north of there at about 3:30 p.m. Chaprales estimated that the sharks weighed about 1,000 pounds apiece.
White sharks are not uncommon off the Massachusetts coasts, state officials said, and they urged swimmers and boaters to use caution.
In other news mentioning the great white shark, the Monterey Bay Aquarium recently supplemented its collection of marine creatures with a great white shark—the fifth since 2004, according to the Los Angeles Times:
It’s a female measuring only 5 feet 3 and weighing just 80 pounds, but she boasts the classic great white look and manner.
She was obtained off Malibu with the help of a spotter plane and commercial purse seiners and it’s hoped those who visit the aquarium to view the shark will come away with a greater appreciation for the embattled species.
The four previous white sharks, which were viewed by an estimated 2 million people, were tagged and released after stays of various length. Scientists tracked them as part of an ongoing monitoring project that also involves other white sharks that were tagged and released without spending time in captivity.
The last captive shark was released from the aquarium after only 11 days and tracked to the Channel Islands area. The previous shark, released after a five-month stay, was followed for an extended period as it swam to and past Cabo San Lucas, then up into the Sea of Cortez off Baja California, where it remained for weeks before its tag life expired.
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According to the National Oceanic and Atmospheric Administration, the “Atlantic bluefish, Gulf of Mexico king mackerel and two stocks of monkfish in the Atlantic — have been rebuilt to allow for continued sustainable fishing.”
Bluefish image by Joe Kunkel. Monkfish image found here
The Food and Agriculture Organization of the United Nations measures how many of each species of each fish were caught each year. Using these numbers, we can see how some fish catches have peaked, meaning that there are simply not enough fish left to catch. Other fish’s catch numbers are still rising, meaning that demand for that fish is increasing: if we keep fishing the way we are, those populations will also start to drop and potentially die out.
—GOOD Magazine
Click the graphic for a larger view. The above graphic is via GOOD Magazine
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Today, I read a very interesting and descriptive court case that discussed the pros and cons of various methods used by the U.S. Army Corps of Engineers to help juvenile salmon migrate from the rivers to the sea, since “it is generally accepted that the Basin’s [Columbia and Snake River Basin] hydropower system is a major factor in the decline of some salmon and steelhead runs to a point of near extinction.” From the United States Court of Appeals, Ninth Circuit:
[D]ams kill some fish as a result of “[b]lockage and inundation of habitat, turbine-related mortality of juvenile fish, increased delay of juvenile migration through the Snake and Columbia Rivers, increased predation on juvenile salmon in reservoirs, and increased delay of adults on their way to spawning grounds.” 57 Fed.Reg. 14,660 (1992).
. . .
Three major methods are employed to help juvenile salmon in their migrations-river flow improvement, spill control, and surface transportation. Each of these methods has its advantages and disadvantages, both for the salmon and the hydropower interests that benefit from the inexpensive electricity generated by the dams. First, the Corps can increase the amount of water released from storage reservoirs and thus increase the flow in the rivers. According to some scientific studies, increased flow decreases the time juvenile salmon spend migrating through the system and reduces their exposure to predators and other adverse effects of the system. The peak natural flow period is in the spring and early summer due to the winter runoff. Increased flow may be of greatest benefit to the juvenile salmon during their downstream migration, which varies from species to species but generally occurs in the spring and summer. However, increased flow in the winter is of greater benefit to the electric utilities because that is when the peak demand for electricity occurs. By adjusting the amount of water that is drawn down from the system of storage reservoirs, the Corps can control the timing and amount of flow to some extent.
Second, the Corps can increase the amount of water that spills over the spillways to allow more juvenile salmon to pass the dams without going through the turbines. Turbines kill or injure a significant number of juvenile salmon in their downstream migrations; thus, increased spill should increase salmon survival. According to some scientific studies, however, increased spill also causes the water to become supersaturated with nitrogen, which in turn may cause gas bubble disease in the fish. But there are economic consequences: water spilled over the spillways does not pass through the turbines and thus does not produce electricity.
Third, the Corps can physically transport juvenile salmon around the dams. The existing transportation program involves collecting juvenile salmon at four dams along the rivers, piping them into barges or trucks, and transporting them down the river past the dams to be released. According to some scientific studies, transportation decreases migration time and avoids exposure to predation and other adverse effects of the system. Critics, however, point to studies suggesting that the transportation program kills some juvenile salmon due to stress from crowding and increased disease transmission.
The Corps currently uses a “spread-the-risk” approach. All juvenile salmon that are collected at Lower Granite Dam (the dam farthest upstream) are transported downstream. At subsequent dams, when the flow in the river exceeds a certain rate which excess is predicted to prevail for at least five consecutive days, the Corps leaves the fish in the river instead of collecting them for transport. Otherwise, the Corps transports the juveniles collected at these dams to a point below Bonneville Dam (the dam farthest downstream) where they are reintroduced into the Columbia River. The transportation program began in the 1970s, and the Corps has operated it since 1981. The Corps transports approximately 20 million juvenile salmon per year, more than half the total number of migrating juveniles.
For more see Nw. Res. Info. Ctr., Inc. v. Nat’l Marine Fisheries Serv., 56 F.3d 1060 (9th Cir. 1995).
Image of juvenile coho salmon is by Brian Lance/NOAA Fisheries.
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