Migratory Macks – Dan Kaggelis August 2016

When anglers think of pelagic fish they typically visualise those species such as mackerel, marlin and tuna which spend the majority of their lives cruising open waters over vast distances away from the bottom. These fish are characterised as ‘pelagics’ because they mostly inhabit the pelagic zone of ocean which is the largest habitat on the earth’s surfaces stretching over 550 million cubic kilometres of water.

Whilst this may seem like a lot of water to move around in, unlike demersal fish which reside on the bottom and rarely travel long distances, pelagics are built for distance with the ability to move with little effort at great speed and cover huge distances due to their streamlined tapered bodies. Known as the great migrates of the sea, these fish will traditionally spend their lives following currents, water temperatures and food sources.
Out of all the pelagic fish species which cruise our waters, the Spanish mackerel would have to be up there with one of the most desirable for trailer boat anglers. They grow to trophy sizes, fight hard, taste great and most importantly can be caught in waters right along the east coast of our great state.

There has been some interesting research undertaken on the Spanish mackerel fishery and from what has been uncovered they certainly do show plenty of attributes which categorise them as a purely pelagic migratory species. To start with like many pelagics they grow really quickly and over a year juvenile fish can reach up to 50cm in length and by their second year they are over the legal size limit. Females are typically larger than males and male fish rarely exceed over 17kg with the life time of a fish usually lasting about 18 years. As mentioned above like other pelagic, Spanish mackerel are migratory. This migratory behaviour is linked to warmer water currents which push down the east coast of Australia during the warmer months. In fact fish tag returns have shown a tendency for fish from up to two years of age to undertake pr e spawning migrations of up to a 1000km in several weeks which is a pretty awesome feat when you think about it. These migratory fish have also shown a tendency to search out particular water temperatures and Spanish will often migrate south along the east coast then back north when southern water begin to cool. Also like other pelagics these fish will seek out and aggregate in certain places to spawn at specific times of the year (typically October and November) and these areas are great fishing spots for those who know when and where to fish them. In fact some of these spots are now in protected zones as you could imagine the domino effect on recreational and commercial sectors all along the east coast if large percentages of the biomass are taken from a single area during a migration movement. Hence we have seen in the last decade the introduction of bag limits and restrictions on netting for these fish to try and sustain a fishery which potentially exists right along the east coast not just endemic to a certain area. It is also worth mentioning the Spanish mackerel is the second largest commercial species behind coral trout along the east coast of Queensland and therefore plays a vital commercial role as well as a social one through recreational fishing.

This is all pretty amazing behaviour and research, but there are also some alternative ideas to consider especially if you put these fish in the one size fit all ‘pelagic migratory’ category. Whilst it is clear that these fish do migrate it seems in some waters Spanish mackerel are becoming far from a seasonal catch and fish especially older larger ones are becoming more residential as opposed to cruising up and down the east coast following the currents. Gone are the days when an unseasonal Spanish catch was a rarity and in some areas many of the fish that aggregate to spawn just don’t leave. Places such as Cape Upstart which were once only seasonal grounds now hold good numbers of these so called ‘residential fish’ all year round. Don’t get me wrong I’m not on about offshore areas like the outer reef which will always hold numbers of fish all year round but those inshore spots some less than a kilometre offshore which usually only hold fish during seasonal runs.   Talking to many anglers who target Spanish mackerel in these inshore areas it seems many are fishing just as good out of season then in season with a mix of both smaller male and large XOS female fish. It begs the question of whether all these fish are migrating or whether there is a substantial percentage which are just moving up and down across shorter distances and staying endemic to a certain area. There are plenty of anglers out there who would agree with this idea of different groups or endemic populations of fish taking up residence along the east coast area as opposed to just a massive migration up and down. These local fish populations are interesting dynamic and it could be argued that better management of the fishery both recreational and commercial in regards to bag limits and the move away from the use of commercial nets has created this effect as residential fish have always been around, they just are around in greater numbers. One argument worth considering is that bait sources in areas have become so prolific that these fish just have no need to leave as they can survive quite easily without having to move with the bait. Other arguments revolve around the clarity of the inshore water and when the inshore waters clear up faster it can lend itself to a longer and more frequent run of Spanish mackerel through inshore grounds.
Whilst the Spanish mackerel will never be classed as a demersal fish or a non migratory species, in some ways they are a very unique species which do exhibit some unique traits and behaviours which don’t fit the pelagic mould. Whilst migration has come into question their life cycle is just as interesting which sees them move around in just about every aquatic environment from estuaries as juveniles to right out on the continental shelf as adults.
Either way they are an awesome fish or if we can begin targeting them all year round that has to be a big win for everyone who wets a line.