Fish Facts

Fish Facts: Giant Herring

Image: Jim Harnwell

ONE of the most explosive sportfishing challenges available in Australia’s tropical estuaries is an encounter with a good sized giant herring (or Hawaiian ladyfish, Elops hawaiensis). Weight-for-weight these fish are exceptional sportfish, combining acceleration, speed and aerobatics into a total package that few other species can match. When you combine this fighting ability with sharp eyesight and a bony mouth filled with fine sandpaper-like teeth to blunt hooks and fray leaders, it is easy to see why giant herring are a formidable foe for fly fishers and light tackle sportfishers alike.

The exceptional speed of giant herring is partly related to their slim build. Even though they grow only to about 6-7kg at their maximum size, they can reach over 1.3 metres long. Even relatively small fish of 2-3kg are up near a metre long. The maximum swimming speed of a fish is related to its body length – so giant herring are fast – having an advantage in this regard over more robustly proportioned species.

A highly predatory fish with large eyes and an oversized mouth, giant herring prey mainly on other smaller fish and crustaceans. Their aggressive nature makes them avid lure takers, with most patterns that resemble prawns, crabs or small fish getting the bites.

Elops hawaiensis is commonly encountered in estuaries and inshore waters of northern Australia, ranging as far south as Spencer Gulf in South Australia and down the east coast as far as Wilsons Promontory, Victoria. But it’s not the only species of giant herring found here. A second species, known as the Australian Giant Herring or tenpounder (Elops machnata) also occurs throughout northern Australia, and indeed both E. hawaiensis and E. machnata overlap in distribution throughout many areas of the tropical Indo-West Pacific region. The two species have been proven based on genetic data, but it can be hard to tell them apart just by casually looking at them as the species are differentiated mainly by counts of gill rakers and vertebrae.

Throughout the world there are seven recognised species of Elops. All belong to the Elopomorpha, which is a primitive group of fishes which also includes eels, tarpon, and bonefish. While adult bonefish, tarpon and giant herring may all appear at first sight to be very different to each other, they all have in common a transparent, leaf shaped larval stage called a leptocephalus larva. Leptocephalus larvae are quite long lived and hence grow quite large for fish larvae, up to 50 mm in the case of Elopsand a whopping 200 mm in some eels, compared to less than 10 mm for the larvae of most other types of fish.

Relatively little is known about the biology of giant herring around Australia, but based on data from overseas we know that adult fish spawn offshore in oceanic waters, as this is where the early stage leptocephalus larvae are found. Over many months these larvae are spread widely by the currents and eventually find their way inshore, after which the larvae metamorphose into juvenile fish and enter estuaries and rivers. Juveniles can tolerate wide ranges of salinity (including water twice as salty as normal seawater), but are more commonly found in waters of low salinity (less than half the strength of seawater up to and including freshwater). The juveniles remain in the coastal wetlands, estuaries and nearshore coastal waters for a few years until they mature, and it is this early part of the lifecycle that makes giant herring vulnerable due to ongoing declines in estuary habitats. Because of their primitive biology and reliance on healthy estuarine nursery habitats, groups such as the International Union for the Conservation of Nature (IUCN) recommend giant herringshould be included with tarpons and bonefishes as target species for catch and release sportfisheries in developing countries in the Indo-Pacific region. Because all of these species have flesh that is full of bones and is relatively unpalatable, this sounds like a good idea to me !


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