I recently enjoyed a Caribbean cruise. I spent a fair amount of my time scanning the sea in search of a surfacing whale or dolphin. I saw nary a one.
I have since learned that whales must surface for air at least every hour, dolphins at least every 15 minutes. With all my scanning, and the (relatively) large surface area I observed, why did I see nothing? You would think these creatures would be popping up all over the place.
The best theory I have come up with is that the proximity of the ship spooks them into remaining submerged. I semi-doubt this, though, because on past cruises I have seen a few dolphins swimming along with the ship.
The Caribbean (and the tropics in general) is not a good place for marine mammals. Marine mammals generally are found in places with lots of food for them, which means areas of high productivity. These tend to be places where upwelling brings nutrient-rich waters up from lower depths. These include Arctic and Antarctic waters and upwelling areas particularly on the western sides of continents like California and Chile.
In Panama, marine mammals, especially whales, are easiest to see on the Pacific coast, which experiences upwelling during the dry season. Although there are dolphins on the Caribbean side they are much harder to see there.
The Caribbean seems to be a fun place for SCUBA diving because there’s so much marine life going on. Is all that life concentrated on just a few reefs near tropical islands, such that the open Caribbean waters are much more sterile (relative to the other places you mentioned)?
Counterintuitively, high-diversity coral reefs flourish mostly in areas of low productivity. Reef-building corals need clear water where light can penetrate in order for the symbiotic algae they depend on to provide them with food.
In Panama, coral reefs are found mostly on the Caribbean coast. On the Pacific they are suppressed by cold-water upwelling during the dry season. (Reef corals prefer warm water.)
It’s often the case that there is an inverse correlation between productivity and diversity. Regions of high productivity are dominated by just a few very numerous species, while areas of lower productivity have a large number of rarer species.
Here’s a map of global oceanic productivity, with red being the most productive areas and blue-violet the least. The Caribbean is comparatively speaking a desert.
On that map, it’s milligrams of phytoplankton per cubic meter of sea water.
Humpbacks migrate to warm water to give birth and to mate. They generally feed very little at this time. They live off fat accumulated in their feeding grounds in polar waters during the winter.
It seems productivity is driven by a mix of currents, temperature, and geography.
Assuming global warming (GW) is real at least one, and maybe two, of those variables are about to shift significantly.
Seeing that the more productive areas are colder, that would seem to imply that warming will be bad for total ocean productivity. The highly productive areas can’t shift too much more poleward than they already are, and the warming is expected to be relatively more concentrated in the polar regions to boot.
Is this valid thinking? Are experts watching and worrying?
My father-in-law lives on the Atlantic coast of Florida (just north of West Palm Beach). He used to have a big boat, and we’d go out on the Intercoastal Waterway in that area. It was very typical to see many dolphins surfacing during those little cruises.
Since this part hasn’t really been commented on -
I’ve seen dolphins jumping in the wake of a boat on a few occasions. They seem to be playing and having fun. I don’t think they stay away.
That was on my Fiji trip. I haven’t been lucky enough to see dolphins here in S. Florida.
Dolphins will often make a bee-line for a boat and follow it for miles playing in the wake. In general, they are not at all spooked by boats except where they have been harassed.
Whales may be a bit spookier but often may be approached closely by small boats.
Caribbean and Hawaiian waters are popular for scuba diving exactly because they are unproductive deserts. That’s why the water is so crystal clear in those regions, which is of course a big attraction for divers. Highly productive waters, OTOH, tend to be murky, being full of, y’know, all that product.
