21/04/2022
Some interesting facts about red emperor to ponder.
Considering they are next on fisheries list to cull the fishing of :(
Red Emperor
Size and age is all about s*x
So in the past, I have voiced concerns about the Red Emperors' recruitment ability with increasing fishing pressure. It’s fairly obvious that numbers, especially of the larger fish have definitely declined over time. When I started fishing Coral Bay a 10kg plus Red was part of the catch every other day. Then it was once a week, and now we only see a few every year. I know one of the reasons for this is because of the areas we fish. We have definitely been pushing deeper over time. With Goldband and other Jobfish making up the majority of our catch most days. This is a good thing, as we are spreading the fishing pressure over a larger area and more importantly more species. I know this is part of the reason we see fewer big Reds. Last year when we had bad currents for most of the second half of the season and fished shallower more often than we have for many years. And we saw more and bigger Reds than we have for a few years. But still not what it once was. And I’m saying this knowing I was not around for the best of it. Most people are aware that Reds are quite a slow-growing fish and this is not going to help the situation. But a while ago I wanted to know a few more facts so I did some research, well tried to. I could only find 2 published papers relating to Red Emperor on the west coast. One from a large study of the trap fishery in the northwest. And the other short one, about just a single fish also from the same trap fishery. I had always known that our Reds don't seem to grow as large over east. Maxing out at about 15kg and anything over 13kg is very rare. Where over east they get 20kg+. It also appeared from the data that our reds seemed to also grow slower and also reach s*xual maturity smaller. A combination of the data started making me concerned about the potential age of our larger red emperor. The largest fish aged in these studies in WA is 7kg and its age is about 20yo. This combined with the oldest fish was 40yo, but with a fork length of 516mm it would have been just under 3kg. So 3kg in 40 years, and I could not find any confirmed ageing of larger Reds 10-15kg on the west coast so I began to speculate on their potential age. If we have a 7kg that is 20yo and a 3kg one that is 40. How old is a 10+kg red potentially going to be, 50, 70? If this is the case, the potential of us shortly getting to the stage where the 10kg red is a thing of the past would be very likely.
I looked into all this some time ago. Since then I have found small bits of info here and there. This combined with me looking at the data from the original study in more depth and what I would like to think is more of an understanding. I have a different overall picture and opinion of the Red Emperors' rate of growth and age. I have since found out about several bigger reds between 12 and 14kg that have been aged at 15-25years old. But how does this make sense if we have a 3kg fish that is 40yo and a large number of fish smaller than this 20yo plus? Well, the answer to this is s*x. As with most fish and animal species, one of the s*xes grows bigger than the other. And Red Emperor are no different. Put simply all the big ones are boys. Not only that the females virtually stop growing around the 40-50cm from length. So females actually max out around that 3kg mark. But the males while the growth rate can start to slow around that size do continue to grow well past it. So that explains why a 3kg 40yo female and a 10kg 20yo Male. This has been well and truly confirmed by my observations with every single large red we have caught, since I learnt how to s*x them at least, has been male. And have not seen a single female that would exceed the 3kg mark. I have further been able to confirm this with the removal of the Otolith. There can be a major discrepancy between the size of the fish and the size and weight of the Otolith. And this all aligns with the s*x of the fish. I have pulled bigger Otoliths out of small 3kg Females than I have out of 6 or 7kg Males. The most relieving aspect of all of this is that it is unlikely that we have Been catching fish that are 50 or 70 years old. But in saying that 30 or 40 is not a young fish. And knowing that fish being spawned now is not likely to be reaching the 10kg mark before I have well and truly finished my fishing career. With the way we are going the chance of any getting there at all is reducing.
So after learning all this it has actually changed my opinion of the venerability of this species. Not only that it has also changed my opinion on what would be considered good fishing practices in regards to the species. The minimum legal size for Red Emperor in Western Australia is 410mm. We have always stuck to our own rule on the boat of a minimum size of 500mm. The main reasoning behind the rule was that at 410mm there is not much of a fillet on the fish. So we release them in the hope they can keep growing to and above 500mm. Now not everyone will agree with me on this but, would you believe it that fisheries might actually know what they are doing in regards to the 410mm size limit. Two reasons for this. First is the mortality rate of the released fish. Between the damage done to the fish during capture/handling and the ever-increasing shark depredation issue. The chances of that fish actually surviving are quite slim. I mean if we have trouble dragging them up to the surface at a rate of knots before they get snapped up by the sharks. What chances does an exhausted one have of getting past them back to the bottom under their own steam? But other than that from what I have learnt a lot of those fish between 410 and 500mm, if they are female might not get much bigger. They would have already reached s*xual maturity and could have spawned several times, and they might be fairly old. So you are not actually achieving much by releasing it. We could say we don’t keep the males under 500mm but considering you need to dice the fish up to s*x it. I don't see that working. So we haven’t scrapped the 500mm rule altogether as 410mm does always seem a little small. But we take into consideration the fish's condition, the sharkynes of the spot and the choice of the angler and find ourselves chucking a few smaller (410-500mm) fish in the esky these days. This opinion is backed by the author of the main study and some others considering size limits as not a practical option to maintain spawning stock. And that more complex management solutions such as closures may be required.
I know things like closures are definitely not what people want to hear. But this is the reason I look into these things is so if the time comes when changes need to be made I want to be as educated as I can on the subject and hopefully help to educate others as well. As unfortunately a lot of fisheries management decisions have just as much to do with public opinion as they do fisheries science. But if we try to keep up with, and understand fisheries science we have half a chance of both the science and public opinion aligning. Because no matter what we all want the same end result. So I’m not sure that we are going to keep seeing as many big reds as we have in the past or currently are. I am much more hopeful we can maintain a healthy fishery and there will always be the odd one that lasts long enough to pull the scales down that bit more.
As always remember, I’m definitely no scientist and this is just as much opinion as fact. So call me out if I’m getting something wrong or let me know if you agree or disagree.
Referenced papers.
Growth, Age Validation, Mortality, and other Population Characteristics of the Red Emperor Snapper, Lutjanus sebae (Cuvier, 1828), off the Kimberley Coast of North-Western Australia
S. J. Newman* and I. J. Dunk
2001
Age estimation and otolith characteristics of an unusually old, red emperor snapper
(Lutjanus sebae) captured off the Kimberley coast of north-western Australia
By S. J. Newman, C. L. Skepper and C. B. Wakefield
2009
Fishing Around Western Australia
