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How the water temperature affects fish

IT is definitely winter in every sense of the word. People are wearing scarves, coats and jackets that are more associated with snow and ice than they are with palm trees and hibiscus. It is that juxtaposition that makes Bermuda something like halfway between truly tropical and truly temperate (when the seasons make marked changes).

The fact that it is getting dark so early and light so late is another indicator that it is winter. On the plus side, the winter solstice is this weekend, on Sunday at 8.04 a.m. local time. On the down side, is the fact that although the days start to lengthen out again, the coldest and worst weather tends to be experienced in January through March.

Those who follow the weather closely have probably noticed that the sea water temperature has dropped markedly over the past couple of weeks. At last look, it was 66°F (or 18.8°C). This is definitely on the cool side for Bermuda and, may in part, be attributed to the fact that the water never really warmed up this summer as it usually does. The plus side to this is that warm water is hurricane fuel and the less of that in August and September the better. No sense in actually attracting these devastating weather phenomena, not that we have a lot of say in the matter.

In any case, Bermuda does claim to have the most northerly coral reefs and that is where this gets interesting. As most people know, coral reefs are live organisms and particularly sensitive ones at that. They are sensitive to sediment, water quality and water temperature. While they thrive in warm water; for instance, there are lush coral reefs in the Red Sea where sea water temperatures actually exceed 90°F they don't do so well in cooler water. Most experts give 61°F (16°C) as the lower limit for coral survival. Happily for us, the water temperature reported in the media is generally taken inshore where the volume of water allows for quicker and more radical temperature swings than the water out on the reef or in the open sea. The greater the volume, the greater the stability, hence the reduced range that sea water moves through offshore. The so-called Sargasso Sea that surrounds us is often defined by temperature – with the lower limit being about 18°C (about 64.5°F)- an extreme tolerated by corals.

The fishing is also affected by the down turn in temperature. The offshore water temperature is within the range of yellowfin tuna and wahoo even though it is not what they prefer. Fish are cold-blooded and tend to have body temperatures equal to the temperature of the water that surrounds them (well, there are a few exceptions to the strict rule and tuna are one of them). Biologically speaking, the body temperature affects the body processes including feeding rates. Think about snakes or alligators, when they are cold, they only eat once in a blue moon. The same must apply to fish. Other considerations for the pelagic game species are such things as migratory patterns. The fish might be supposed to be several hundred or even a thousand miles south of our location but, for whatever reason, they are late in making the southward journey. Fish on the move are usually fish that need food because they are burning up energy as they migrate.

The really queer thing is that some of the wahoo and probably the blackfin tuna are resident year-round. The reason for this is that they are probably loathe to leave a food source.

Another way of taking a lemon-like situation and making lemonade is to look for species that occur in the area and which actually prefer cooler water. One of these is the albacore. A member of the tuna family it is usually found at depth here because the water is cooler and that is what they like. Years ago, there were quite a few Taiwanese longliners that frequented the area from November until about March and the whole point of their effort was albacore for the cannery trade. In a conversation with a Chinese skipper, he informed all who would listen that the preferred temperature for albacore was 61°F (16°C), something which has been borne out by other sources.

Although the offshore surface temperatures don't drop that low, there is less of a depth factor to achieve that temperature, so it is more likely that surface fishermen (trollers and chummers) are going to encounter albacore. In fact, there is little doubt that albacore are caught here regularly and there are probably a fair few misidentifications; probably as blackfin or other tunas. If in any doubt just look at the length of the pectoral fins, when spread they resemble airplane wings! The meat is also the whitest of any tuna and a definite treat.

The main problem with going in search of albacore is the weather is lousy and sport fishing effort drops to its annual low over the next couple of months with even the commercial operators trimming back their offshore effort, usually concentrating on lobsters instead. A few others stick to working the Banks with a spot of trolling for wahoo and then concentrating on drifting for whatever might be willing to please.

Probably the most reasonable fishing to be done when the weather and other considerations permit, is to work the reef areas in search of fish that make for nice fillets and the occasional grouper species large enough to use whole. Red hinds are the most likely candidates and it should be possible to scare up a few. Sending some chum on down to the bottom can often liven things up. Apart from the bottom dwellers, there should be some bonitas or amberjack around and it is not too late for the odd yellowtail to put in a appearance. All very welcome when ham, turkey and cassava pie are the main menu items.

It is highly unlikely that the next couple of weeks will see much in the way of fishing. The emphasis is on getting prepared for the festivities and, along with those social events, there is no shortage of excuses for staying onshore. A quick look at the North American weather scene and it is likely that sea conditions will not be overly conducive to a run offshore but you never know until the day. Just remember, if you get the weather and can get out, it is possible to stay quite close to home and still manage some Tight lines!!!