BajaNomad

Baby Blue Marlin

Bob H - 6-9-2013 at 10:09 AM

It's hard to believe that this newborn Marlin could grow to over 2,000 pounds.



Like most open ocean fishes, blue marlin are broadcast spawners. Females release their eggs, and males their sperm, into the open ocean, and fertilization takes place in the surrounding water.

There is no parental care of the young. The eggs float until the tiny larval fish hatch out, probably one to two days after fertilization.

Obviously, with this kind of reproduction, great numbers of eggs and sperm are needed to guarantee that some fertilization takes place, and that there are enough young produced to offset the high mortality early in life. Many eggs and larvae fall prey to tiny predators in the plankton.

The annual egg production of female blue marlin produced per year range from 30 million eggs for a female of 400 pounds to 100 million eggs for a female of 950 pounds. The larger (and older) a female is, the more eggs she can produce.

The great energy it takes to produce all these millions of eggs each season may be part of the explanation of why female blue marlin reach much greater sizes than their mates. Large size may be necessary if marlin are to “afford” reproducing in this way. The faster growth rate for the females thus helps them attain large size, so that they can reproduce enough to perpetuate the species.

The eggs of blue marlin are quite small, only .05 inch (1.25 millimeter) in diameter when ready for spawning. However, not all the eggs in the ovary are the same size, and they are not all ready for spawning at the same time.

There appears to be six batches of eggs in the ovary at the beginning of the spawning season, each batch a slightly different size and age. A female probably spawns several times in each season as the successive batches of eggs mature and become ready for release.

Spawning many times during the season is part of good strategy for reproduction... never put all your eggs in one basket, so to speak. If one batch of eggs fails, one of the others may be successful.

To ensure that the female’s millions of eggs are fertilized, male marlin must produce large numbers of sperm. Sperm count estimates range to over one billion sperm cells per cc (milliliter) of milt. The volume of milt stored in the sperm ducts varies between males.

A large male in spawning condition may produce as much as 200 billion or more sperm cells. The amount of milt released during a single spawning has not yet been determined, but billions upon billions of sperm may be needed in order to be sure that fertilization occurs.

If the male marlin’s reproductive output is so large, why aren’t males as big as females? The difference lies in the energy investment needed for the production of eggs and sperm, and in the timing of their production by the different sexes. Sperm cells are very small and are probably “cheaper” to produce than the eggs. And, while the females produce all their eggs at the very beginning of the season, males can produce sperm cells continuously throughout the length of the season, spreading their effort out.

The lower cost of reproduction for the males has been suggested as an explanation for their smaller size. Presumably, they simply don’t have to be big.

The study of marlin reproduction may provide answers to questions about the factors important in the reproductive success of marlin populations and the ability of marlin populations to replace themselves.

Blue Marlin

Osprey - 6-9-2013 at 10:20 AM

Bob, with your permission:

Size Does Matter



Although I’m a long-time salt water fisherman I have not spent much time thinking about Natural Selection and the creatures of the sea. I do know that some creatures are so prolific that their offspring are truly “uncountable”. I know also that others have a very hard time producing more of their specie—problems with fertilization, egg-laying, identification, sexual orientation, etc.

One problem sticks out for me because it involves billfish. The typical female blue marlin is four times larger than her male mating counterpart in the wild. I try hard not to anthropomorphize everything when it comes to the animal world—using human or primate benchmarks and asking stupid questions about “our differences.”
.
With the blue marlin I might make an exception: it might be fun and meaningful to imagine the difficulties encountered by humans if the female were four times as large as males. Now, let’s be adults and keep the tittering muted, please. I have caught a few blue marlin. The creatures are difficult to sex identify and I have never tried. They were released or, in the case of the small, tasty ones, prepared for the table. I’m going to guess there are many, many huge adult female blue marlin. That means the small ones which are caught or tagged or observed are either juvenile females or adult males—my guess infers there are no really large males.

There are those who say “pound for pound” the large ones put up the most ferocious fight of any billfish. Might it be safe to say “female blue marlin fight like they have an attitude?” Might one conjecture that “most of the time, when hooked, they appear to be extremely agitated as in a heightened state of anxiety?” Should one wonder if the cause could be frustration, i.e.” perpetually unfulfilled? (polite Blue Marlin might employ the term underfertilized ).”

Of course you can’t really get into physiognomy when thinking about this because we are land animals. If the average woman was 4 times larger than an average man he would need a ladder just to climb up into her lap—at 23 feet or so she would tower over him and outweigh him by hundreds of pounds. As to procreation he would be, how shall I say, “overwhelmed” by their differences.

Marine scientists believe the marlin’s bill is used for striking its prey, for injuring small fish so they can more easily be caught and eaten. I think that holds true for the large females. I think the bill of the male is used almost exclusively for tickling.

[Edited on 6-9-2013 by Osprey]

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DaliDali - 6-9-2013 at 10:26 AM

Quote:
Originally posted by Osprey

If the average woman was 4 times larger than an average man he would need a ladder just to climb up into her lap—at 23 feet or so she would tower over him and outweigh him by hundreds of pounds. As to procreation he would be, how shall I say, “overwhelmed” by their differences.

[Edited on 6-9-2013 by Osprey]


Pretty much cuts out the "cowgirl up" position.

[Edited on 6-9-2013 by DaliDali]

Bob H - 6-9-2013 at 09:37 PM

Osprey, you always continue to amaze me with your take on things. Human women would be huge if the same size difference applied to us... wow... who would have thought of that, but you! I am trying to picture it in my mind.

And, yes, size would matter, big time!!

Skipjack Joe - 6-9-2013 at 10:27 PM

You may find the theory of r and K selection interesting:

http://en.wikipedia.org/wiki/R/K_selection_theory