The Cobia Rachycentron canadus is the only member of its family Rachycentridae. It has a worldwide distribution and is highly prized sportfish targeted for its superb fighting and eating qualities.
Cobia are a subtropical to tropical species and in WA they are occasionally found as far south as Rottnest Island, however they are more often found north of Dongara. In the far north of the state (Port headland and Broome) schools of large cobia can be encountered during “the dry season”.
Cobia are an excellent table fish with firm white flesh that is similar to that of Spanish mackerel. However, as with all pelagic fish, a quick spike to the brain followed by bleeding and gutting before placing in a seawater / ice slurry will dramatically improve its eating qualities.
Cobia fillets freeze well for long periods which is handy if a large specimen is taken. As with spanish mackerel, cobia are suited to most cooking styles whether it be smoking, deep or shallow frying, barbecuing or for use in casseroles and curries as the flesh will hold together well.
The minimum size limit for cobia is 75cm in WA waters with a bag limit of 2 fish per diver per day. This species is part of the "High Risk Pelagic " group so remember in the West Coast Bioregion you may only take a combination of 2 fish from the entire high risk pelagic list per day! For current information please refer to http://www.fish.wa.gov.au/docs/pub/RecFishArrange/FAQ-Nov%202009.pdf
Characteristics and habitat
Cobia are distinguished by having a broad flattened head and a long cylindrical shaped body. They are chocolate brown to black with white underneath. Cobia can also have two horizontal white stripes running the length of the body. These stripes fade with age. They have a large tail, which becomes more forked with age and the upper lobe larger than the lower. The second dorsal fin is peaked and continues on towards the tail. This prominent second dorsal fin, the large pectoral fins, the larger upper tail lobe, and the flattened head all combine to give the cobia a shark like appearance.
Cobia are quite a large pelagic fish growing up to 68kg in weight and a length of 2m. The maximum recorded age for the species is 15years which means that they have a very high growth rate. The world spearfishing record weighed 54.5kg and was speared in Brazil by Jaime DaSilva in 1997. In 1985 a 61.5kg cobia was caught by a line fishermen in Shark Bay WA. In WA Cobia are generally between 6 and 15kg with anything over 20kg regarded as a prized trophy. The current WA state record is 35.75kg was taken by Scott Paxman in 2008.
Cobia are mostly encountered singularly or in small groups but on occasions they can form large schools. They favour reefs, particularly those adjacent to sand, where they are found swimming fairly close to the bottom. It is not unusual to see them found lying on the bottom primarily on sand.
Cobia also have an affinity for floating debri, pylons and marker buoys. It is well known that cobia are often found travelling with other marine creatures such as manta rays, stingrays, turtles and large sharks particularly tigers and whale sharks. It is advisable to have a closer look at any large marine creatures that you may encounter. That huge remora that you saw may in fact have been a decent cobia.
Cobia, especially large specimens, are easily mistaken for sharks. Hard luck stories abound from divers who have seen what they though was a shark only to have realised that it was a big cobia after it was too late.
Like with most pelagics, cobia should be approached cautiously and as silently as possible. Always try to avoid direct eye contact as well as any sudden movements that could spook the fish. Cobia fight very hard once shot and have great stamina. This combined with their relatively soft flesh means that they often tear free. A shot from directly above just behind the head would be ideal. Make sure that you don’t shoot cobia in the head as their heads are extremely hard and your spear is likely to bounce straight off. A side on shot where the lateral line meets the gill plate would also be excellent. Avoid gut shots and shots further down towards the tail as the cobia will get a better fighting advantage and most likely win its freedom. If you can’t get a good shot on a big cobia it is best not to shoot it as it as we all have a responsibility to minimise the amount of fish lost from a spear.
One technique employed on the east coast to bait an area with fish frames the afternoon or night before. Choose a suitable location that is known to hold cobia at times. Headlands are particularly good especially if they front deep water close to sand. Put the fish frames out over sand if possible and then return early the next morning. It is a great use for any old fish frames which can be kept and frozen for future use.
The burley may attract cobia outright but if not large stingrays will hopefully be drawn to the area and with a bit of luck you might find that they have a cobia entourage. This is not a technique often employed in WA (mainly due to the fact that most divers are based a long way south of cobia “hotspots”) but would probably work here as effectively.
Once shot Cobia head straight for the bottom and love to roll in an effort to free themselves, badly bent shafts are normally the result. If you are able to shoot one over the sand it is simply a matter of playing it out slowly until it can be easily pulled up. If in a reefy area you may need to put more pressure on the fish if it is likely to get caught up. Often when a cobia is speared off a ray that is swimming along the fish will take up its position again in the slipstream and they can be very hard to pull away. Also be careful not to hit the ray as well as you could find yourself in all sorts of trouble.
A powerful gun from 1.2 to 1.5m is needed for cobia to penetrate their torpedo shaped body. Use double 16 or a single 20mm rubber with a 7 or 7.5mm spear. Many diver like to use 3/8 spears for these fish although these fish seem capable of bending any spear if hit badly. A reel with at least 30m of line or a rig line / float setup are vital for these strong fish as they can easily pull the gun from a divers hand (or pull the diver under if they hang on!). You will also need a strong sharp knife to get through their extremely hard heads.