ENVIRONMENT: Size limit issues revisited

LATELY we’ve been landing some nice rock blackfish and silver drummer on our luderick tackle. The silver drummer are all released as almost no one reckons that they’re worth eating. While they’ll take a green weed, cunjevoi or prawn bait when they’re in the mood, they’re primarily vegetarians and their favourite food appears to be the iodine-rich brown strap weed that often grows next to the green lettuce used for luderick and rock blackfish. That presumably accounts for their lack of appeal as a food fish. So, as they’re not kept, in NSW there are no size or bag limits set for them.

It’s a different story for the rock blackfish, also known as the pig or black drummer. As many have written previously, they are really good to eat. The smaller fish, up to a kilo or so, bake or roast beautifully whole. The bigger guys, ideally around 2-3kg, yield lovely thick, firm, white fillets. Unlike the silvers, in NSW there are size and bag limits for the blacks, 30cm and 10 fish respectively.

Years back my mates and I targeted big pigs a lot. For a most of us, 12lb or around 5.5kg was our specimen target, bit like a metre barra up north. 4 to 4.5kg fish were often taken, mainly on cunjevoi or cut crab, and silver drummer to 6kg were often part of the by-catch. Pigs of all sizes head for caves or reefs when hooked, so landing a good one on luderick tackle is always an achievement. Silvers don’t do that but do run over rocks and kelp beds and often cut you off. Both species have teeth sharp enough to bite through light luderick leaders, so most landed tend to be lip-hooked.

But back to the size limit issue. The Australian record silver drummer was around 14.4kg, nearly 32lb. It was speared. The rock blackfish record is a bit over 9kg, nearly 20lb, and was line-caught by the co-founder and first editor of Fisho magazine, the late Ron Calcutt, many years back. That’s about a 75cm fish.

So, should the size limit stay at 30cm? The best piece of work on rock blackfish I’m aware of is a PhD thesis by Jerom R. Stocks from 2015. He suggests that female rock blackfish don’t hit sexual maturity until 39cm. So, if the size limit objective to let at least 50% hit spawning age, then logically the minimum size should be 39cm. But it’s more complex than that. If you go up to 39, then more of the retained fish will likely be females, as currently fish between 30 and 39cm that are kept are probably going to be males. Jerom suggests that without further work on population modelling, raising the size limit may have the unintended consequence of further stressing the rock blackfish stocks rather than preserving them.

Maybe a better strategy would be to halve the bag limit. And have a slot limit of 30 to 40cm. It’s been done for blue groper and dusky flathead in NSW and talked about for barra up north. Rock blackfish are slow growing and easily depleted in specific areas when targeted with modern high-tech tackle and methods. It would be tragic to see them go down the same road that bluefish (blue drummer) took in NSW, the road to near extinction. Time to consider slot limits and a lower bag limit for the rock blackfish, DPI Fisheries?

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