Why only males

[adam333]

Went out on the Severn yesterday.  Caught 40 males and one female.  Why such the high male ratio ?

[BJ1fish]

You must be crabbing in an area with low salinity level. Male crabs live in low salinity and females high salinity levels.

[im2fast4you33]

To add onto that, females also dwell in deeper sections.  Probably because of salinity levels.

[Neither Crab]

If someone wants to fact check this, be my guest. I read in the book catching crabs by the bushel  that female crabs enter fresher water late in the season because it is a primary breeding season.

[jack1747]

"Range (for Chesapeake Bay)

Blue crabs are found from the mouth of the Chesapeake Bay to tidal fresh areas. There are distinct differences in the ranges of males and females. During the summer months, males are found from freshwater to the polyhaline zone (waters with salinities of 18-30 ppt), although they occur in the greatest numbers in salinities of 3-15 ppt. Maximum numbers of females occur down Bay at salinities of 10 ppt to ocean salinities."

"After the female matures and mates, the newly molted "sook" must regain strength and build muscle mass in order to prepare for her migration to high-salinity spawning grounds where she will produce a "sponge" and then release eggs. To prepare for this journey she will remain and forage in the same general area where she mated for a period of weeks to months (Turner, Wolcott, Wolcott, and Hines 2003). It isn't until late September or October that she will begin her migration to the lower Chesapeake Bay to spawn. The "pregnant" females that survive the gauntlet of crabpots, scrapes, trotlines and dredges will usually spawn for the first time the following season since they reach the spawning grounds late in the season. In other words sooks won't release any eggs until approximately 2-9 months after mating, usually May-August the next season."

[twharrell]

Here's a good salinity map of the Chesapeake:

Spring: http://www.chesapeakebay.net/maps/map/chesapeake_bay_mean_surface_salinity_spring_1985_2006

Summer:
http://www.chesapeakebay.net/maps/map/chesapeake_bay_mean_surface_salinity_summer_1985_2006

Fall:
http://www.chesapeakebay.net/maps/map/chesapeake_bay_mean_surface_salinity_fall_1985_2006

So, you were crabbing waters that were 5-10 ppm, perfect for jimmies

[evinrude 130]

This article tells a somewhat  different story on when they spawn.  They spawn down near the ocean were the salinity levels are good. So if they are spawning later then April(according to this article) they must be staying close to the ocean for that perfect environment to spawn.  Which could mean later in the season also.



Heavy lifting for females

Adult male crabs are brawny, but the weight of maintaining the habitat falls on females. They do the heaviest lifting, by far, in a yearly trek to replenish the species.

After they mate from May to early October, nature beckons them to the mouth of the bay. Depending on where they depart in the estuary, pregnant females known as sooks migrate as far as 150 miles to get to a spot in the lower bay near the salty Atlantic. Their offspring have a higher rate of survival in waters with elevated levels of salinity.




Walking on six skinny legs and swimming with two tiny flippers, the perilous trip takes the entire fall.

“They’re all moving down . . . waves of females” from as far north as Havre de Grace, Md., said Romuald Lipcius, a professor of marine science at the Virginia Institute of Marine Science, who studies crabs. The epic migration puts the more storied march of emperor penguins in Antarctica to shame.

In a bay choked by pollution, killer invasive species and hundreds of fishermen, every step could be their last. They dodge crab pots, predators such as striped bass and red drum, and polluted dead zones where water lacks oxygen.

“It’s an amazing thing,” said Anson “Tuck” Hines, director of the Smithsonian Environmental Research Center. “You can think of it like a migration of birds, except they’re not moving in a flock.” The bay is huge, so “they’re not shoulder to shoulder,” but scattered out, “moving as individuals.”

Females burrow in mud and stay almost perfectly still in winter to conserve energy at a time when food — oysters, clams, mussels, snails, insects, worms and some fish — is scarce. After the thaw, they move closer to where the bay’s fresh water meets the salty Atlantic.

Each female lays between 750,000 and 3 million eggs starting in late April, but an average of only one in each brood is likely to live.

The hatchlings take the form of microscopic shrimp that fan out to the continental shelf in the Atlantic in the early stage of life. After a month, they grow to look like lobsters the size of pin heads and ride flood tides northward into the bay. At the end of summer, they become juveniles that finally take the typical shape of a blue crab as they walk up the bay in grasses on the floor.

They journey north on fall flood tides — and at every stage they are a tiny crab feast, disappearing into the mouths of virtually everything that swims, including bigger crabs.

Considering the importance of the event, Mullis said he doesn’t understand why officials allow females to be harvested shortly after the fishery opens in March.

“I feel there are too many sponge crabs going to market,” Mullis said. Females carry up to 2 million eggs each in a foamy sack called a sponge. There should be a moratorium on collecting them, he said: “Somebody needs to stop carrying the pregnant mothers to market. They are keeping millions of eggs from hatching.”

Bull said that in cutting the number that can be harvested by 10 percent, Virginia was trying “to not put a debilitating hardship on commercial crabbers” trying to make a living. “A rule of thumb,” he said, “has been that if you ask 10 watermen their opinion on one issue, you get 30 back.”

Beautiful, savory swimmer






























 
 






 

  


 






    




 





  







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[Neither Crab]

Not spawning , laying eggs, breeding, when lots of females come up the bay into fresher water during September and you see lots of doublers swimming together on the surface . Very good post A+.