COLLAPSIBLE FRAME NET
Please let me finish this long essay before you post a comment, so this posting stays intact. It will take a few days for me to finish this posting since I’m away from home for a couple of weeks R&R. I’ll signal completion with the word finish when completed.
We had just ended the hurricane season and Tropical Storm Fay had Drenched the Lagoons and surroundings with over 24 inches of rain as the storm seemed to stall in the area for 2 days.
Comes start of dipping season and no significant shrimp catches were to be had, No one really knew why. So I started a thread in December 2008 with the question of the day …….
Where are the shrimp?
Don't tell us which supermarket we should go to.
Think about why the scarcity of shrimp so far this dipping season.
Has anyone noticed, other than me, the start of shrimp runs are way behind schedule this season? Our reports of catches are pathetic for the most part, despite good moon phases? Cold fronts breezing through? Cypress trees shedding leaves?
Where are the shrimp in our usual productive haunts this season? What are we doing wrong or different this season? Can't pinpoint it? Neither cauld I.
So I started back on some basics - CaptLee talked about this to a little extend on the Fishing Radio show. What is the life cycle like for a shrimp?
It's also like what Captain Leo teaches, but there are some key points missing - in fishing, you can use all the right lures/baits, rods. reels, a quiet boat, technique and presentation. But it won't make you a good fisherman if you don't know where the fish are, when they are there, what they'll eat that's there. In short, you need to understand your fish and their environment.
Same for the shrimp.
Shrimp spawn close to shore, and prevailing winds and tides carry the brine shrimp eggs into ML and IRL where they hatch and find sea grasses for shelter and food. They grow up there until they reach a point that they migrate back into the ocean to complete and repeat their life cycle.
I know, this is a simplistic explanation. But here is where it starts to get interesting. What causes shrimp to lay eggs close to shore, and what causes the shrimp in the lagoon to migrate back out to the ocean?
What's the basic trigger mechanism that starts this cycle over and over and makes it successful. What environmental factors are at work?
The little research I've done to find an answer has a lot to do with physical factors over which we have no control - the amount of sea salt (salinity) is in the ML and IRL. How does salinity affect the brine shrimp hatch? Does salinity have an effect on shrimp migration?
One of the interesting pieces of the puzzle I fount is the salinity does indeed influence the hatch, from small hatchings in no salinity to little hatching for too much salinity. There is an optimum peak hatch for a narrow range of salinity of 20 to 40 ppt (parts per thousand) - similar to the ocean salinity. Here is a link to the experiment that answered this part of the puzzle for me.
But wait – the average lagoon salinity is very similar to the surrounding ocean water, despite large distances between inlets and the lagoons. There is a large variation in salinity from season to season, due to the amount of rainfall over the lagoon and surrounding areas. During drought conditions, the salinity increases due to evaporation of lagoon water. During wet seasons, the salinity decreases due to rain and runoff exceeding the amount water evaporated.
Marine life can adapt to a large range of salinity. But comes under stress if the salinity really drops, such as occurred during Tropical Storm Fay on August 20, 2008. Fay dumped about 24 inches of rain in 2 days over Brevard County. And then, add the runoff from surrounding lands and drainage ditches. It took a couple of weeks for water levels to get back to near normal conditions Salinity probably longer.
I would suspect the salinity drooped so near record low levels. Probably 1/3 normal salinity or less on average, much lower in shallow spots. Extreme/fatal stress for some marine life in many locations.
Shrimp eggs entering the lagoon during this period – expect reduced hatches. Juvenile shrimp – expect some mortality due to sudden change in salinity in the sea grass beds. I know from what I’ve researched, farm raised shrimp are raised in lower salinity than ocean salinity, but these shrimp were more gradually acclimated to their lower salinity. That, and artificial feed gives these shrimp their bland taste.
This is an interesting read that suggests how shrimp navigate upstream and downstream, and behavior in distribution of larva and juvenile shrimp to differences in salinity. The full text of this abstract is a difficult read and hard to comprehend, but it suggests lower salinity strata in the water column causes Juvenile shrimp to hug the bottom of the water column. I have to re read this to be sure I got it right.
http://www.biolbull....stract/136/1/43
The author also suggests that lowered salinity really affects the next year’s crop of shrimp as the results were based on juvenile shrimp that would be harvested the following year.
OK – given all this information, have the hurricanes in 2007 and particularly hurricane Fay this year caused the late start of the shrimp dipping season, or should we be breaking out the box nets to get the shrimp that are lower in the water column. Are we missing a bet that the shrimp run is in full swing, but we don’t see them because of more favorable water conditions lower in the water column?
End of Part 1
