Sunday, December 14, 2008
An interesting article by Doug Pemberton - Diver Magazine
The coast of British Columbia is renowned for it's incredible diversity of colourful, rare, and bizarre marine life. And if there was one animal that has become a symbol for diving in these waters, it would have to be the rockfish. With some thirty species inhabiting the northern Pacific they account for more species than any other genus of fishes. Over a dozen species can be encountered by recreational divers while the rest are found in depths down to 2000 metres.
Their variety in size and colour covers a great range. Some advertise their presence through bright colours and vivid patterns, while others strive to be less conspicuous through indistinct colouration. Maximum sizes vary from under 20 centimetres up to nearly a metre and they can weigh from less than half a kilo to over ten kilos.
Unlike most fish, rockfish do not lay eggs; they give birth to live young, usually in the spring and early summer, but some species also give birth during the winter. Depending on the species, and size and age of the female, anywhere from 10,000 to over a million young may be released. The tiny larvae become part of the plankton soup at the surface where many are consumed by larger animals. After a few weeks, survivors slowly make their way into the depths where, depending on the species, they may adopt a solitary lifestyle or live in large schools with other species.
Rockfish are very long lived with some living in excess of 100 years, and some species may not become sexually mature until they are ten or twenty years old.
Unfortunately, some species reach a harvestable size before reaching sexual maturity. Most rockfish also have a small and limited home range in which they spend their whole lives. This combined with the fact that they are relatively easy to catch makes them easy targets. And, unlike many other marine fish, an undersized or unwanted rockfish can rarely be released after capture because its gas bladder expands so rapidly during ascent due to the changes in pressure that, by the time it reaches the surface, a rockfish is so severely bloated that it is unable to swim, if not already dead . And therein lies the problem. Stocks have steadily been declining, putting the status of BC's rockfish in peril.
Over the past decades I, like many divers, have seen a slow and steady decline in many rockfish populations. Black rockfish were so numerous at some sites that they were a nuisance, always getting in the way when I was trying to get a picture of something else. Now, at those same sites, I have logged sightings of four black rockfish over the past five years. At some places schools of yellowtail rockfish were so thick you couldn't see through them. Today you have to look hard just to find a few. And these now include some of our previously most common and well known species such as the quillback, copper, tiger, china, and yelloweye rockfish. The decline can be attributed to one main cause: commercial and recreational over fishing. And now fisheries are targeting some deep water species that we know next to nothing about.
But there are things that are being done and things that are helping. One thing I have noticed while diving some of BC's artificial reefs is healthy populations of juvenile rockfish. On one wreck, vividly striped juvenile yelloweye rockfish are almost a common sighting. These ships are definitely a benefit when it comes to providing a safe habitat for young rockfish and many other species as well.
In an effort to protect the dwindling stocks, Fisheries and Oceans (DFO) has now established Rockfish Conservation Areas (RCAs) throughout the Strait of Georgia and inshore waters between northern Vancouver Island and the mainland. These RCAs are subject to change as the need arises.
Education is an important part of protecting any species and in order to inform boaters, fishermen and divers to the plight of rockfish, DFO has published a free pamphlet and booklet that explains the need for these measures, provides interesting information on the various species under protection and includes detailed maps and co-ordinates of the RCAs. Realization of the problem and an understanding that measures must be taken is an important first step.
The problems facing the BC rockfish are not unique. Unfortunately fish stocks are on the decline around the world and the measures instituted by DFO are expected to be in place for a number of years.
The decline of any species should act as a reminder of our profound effect on the fine balances that exist in nature. Hopefully, and through action and education, the rockfish of BC will continue as the symbol of the fantastic variety that makes up the BC marine environment.
Source: Doug Pemberton. Diver Magazine