Fish Facts

Fish Facts: Black bass research

WHEN you mix a cocktail of large snags in fast flowing rivers together with remote steamy tropical jungles north of Australia, you come up with a recipe for sportfishing excitement called black bass fishing. However, the legendary black bass is not a bass at all, indeed it is a Lutjanid as evidenced by its appearance and its scientific name Lutjanus goldiei.

Also known as nugini bass and Papuan black snapper, L. goldiei was originally recorded only from Papua New Guinea, firstly from the Port Moresby district and the Fly River. But now it is known they also occur along the north coast of New Guinea, through New Britain, Bougainville, Borneo and even as far east as the Solomon Islands.

Black bass are clearly members of the Lutjanid family and present as a larger and chunkier “mega” version of the mangrove jack (L. argentimaculatus). They possess a similar body plan to jacks, including large canine teeth and powerful jaws, but differ due to their dark brown to charcoal grey-black bodies, fading on the lower sides and belly to golden-brown. Young black bass can have pretty blue undulating lines around the eyes that fade as they mature, while the fins tend to be dusky brown to blackish, sometimes with a yellow hue.

On snags inhabited by both jacks and bass, there is no doubt which species rules the roost. Many an angler has been lulled into a false sense of security by taking one or two of the faster mangrove jacks from a PNG snag, only then to be comprehensively blown away by the larger, darker shadows underneath. Both species can grow to a maximum size over a metre in length, at weights exceeding 15 kg for mangrove jacks and 20 kg for black bass. The difference, it seems, is that mangrove jack move to offshore reefs much earlier in their life cycle once they mature, and do not return such that it is rare to catch them much bigger than 60 cm in rivers. In contrast, very little is known about the life history of black bass, but it seems while they might make brief seasonal migrations to nearshore or offshore reefs to spawn, large adult black bass certainly occur in rivers and estuaries and indeed may move back into rivers after spawning.

Having said that, scientists know very little for certain about the lifecycle and biology of this species. Because of the need to know more about black bass in order to properly manage the massive potential for sustainable sportfishing tourism for this species in PNG, one of the first dedicated research projects targeting this species is being undertaken by the Australian Centre for International Agricultural Research in cooperation with PNG Fisheries and Tourism authorities. Some of the questions being asked by the scientists include how fast do they grow, how long they live and of course, if, when and where they move. Although it is early days yet, the research project is already uncovering some interesting black bass facts.

Initial indications from studies of morphology and chemistry of black bass otoliths (ear bones) suggest that they are relatively slow growing and long lived. A 77 cm black bass was estimated to be 18 years old, while several fish between 44 and 73 cm were between three and 10 years old.

Otolith chemistry suggests they have a complex life history similar in many ways to other lutjanids. It appears that spawning occurs in areas of high salinity (e.g. coastal marine waters) after which larval and juvenile black bass move rapidly into freshwater for several years during early life. They then appear to move back down near river mouths at the onset of maturity and make periodic migrations back into high salinity waters, possibly for breeding. The researchers hope to verify these theories using acoustic tagging, while also conducting further research on growth rates and longevity.

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