Sweep – Scorpis lineolata

Sweep – Scorpis lineolata also called False Pompano

Description

The sweep – Scorpis lineolata is grey in colour, darker on the upper body, and silvery on the sides and below. There is a black rear margin on the gill covers, which from a distance, may appear as a spot. The leading edge of the tail is black in colour, as are the tips of the dorsal and anal fins. The body is laterally compressed. 

The mouth and teeth are small. 

The lateral line has a slight curve. 

Found in temperate waters ranging between 13.0-25.°C 

Sweep is known to reach a maximum length of 36cm (about 1.18 ft) and a maximum weight of 1.5kg (3.3lb).  

According to Andrew Stewart, Assistant Curator NE (Fishes), at Te Papa Tongarewa, Museum of New Zealand, the sweep can live for over 50 years! Estimates of age are calculated by counting growth rings in otoliths. Otoliths are found in the ears of fishes. They are rocks, not bones. Sweep can live a very long time. The maximum recorded age is 54 years.  

Growth in their early years is quite rapid and they reach sexual maturity at 2-3 years of age. By which time they are about 17 cm in length. Once they reach maturity their growth rate slows considerably. They can therefore have a very long reproductive life. This is relatively unusual for fish. Studies by fisheries scientists in Australia have shown that the three-year age class is the most abundant. 

Approximately 50% of the fishery comprises fish older than 15 years, and more than 20% comprises fish older than 30 years – see reference below: John Stewart & Julian M. Hughes (2005). 

Silver sweep is closely related to the blue maomao. 

In New Zealand, spawning takes place during May and June. 

Angling 

Anglers in northern New Zealand generally regarded small sweep as a nuisance fish that will strip bait from hooks intended for larger fish, a habit they share with the spotty. However, a larger pan-sized specimen is a welcome addition to the anglers’ bag. 

Although they are plankton feeders, they will readily take a small size 4 hook baited with molluscs, crustacea, squid and octopus. Their small mouths mean they are difficult to catch making small hooks essential.  

A proven way of catching sweep from the rocks in Australia is to use a stoppered float rig which makes it possible to fish any depth. Use a three-hook rig with enough lead weight for casting but not too much so it doesn’t pull your cork float under. 

Distribution 

Sweep is found down the east coast of Australia from southern Queensland south (including Tasmania) and northern New Zealand. It is widespread around New Zealand but is more common around the North Island. Silver sweep are generally residential and can therefore be depleted by recreational and commercial fishing over their more readily accessible rocky reef habitat. 

Possibly, because of warming sea temperatures, it is now found more often around the South Island than it was. They can be caught at least as far south as the Banks Peninsula.  

Silver sweep in New Zealand is always found over rocky inshore coastal reefs. Smaller juveniles can be caught very close to shore from rocks, wharves and jetties. Juveniles also enter brackish water and estuaries. Depth ranges from 1m to 30m. 

The specimen shown in the photographs above and below was caught by Ryan Adams in a crab opera house folding net at Purau, Lyttelton Harbour. The pot was baited with a tin of sardines. 

If you have caught a sweep, we would be interested to hear about how big it was and whereabouts you caught it in the comments below.  

Schools of the mature silver sweep are often seen mid-water feeding over reefs and rocky areas. Sweep is often found together with the closely related blue maomao – Scorpis violaceus. 

What does silver sweep eat? 

Sweep – Scorpis lineolata are plankton feeders. In northern New Zealand, the sweep and the related blue maomao are the main inshore plankton feeders.  

Are sweep fish good to eat? 

Silver sweep are very good eating. They are not usually targeted by anglers and are more likely caught by accident while fishing for other more desirable species over rocky reef areas.

References

John Stewart & Julian M. Hughes (2010). “Longevity, growth, reproduction and a description of the fishery for silver sweep Scorpis lineolatus off New South Wales, Australia”. New Zealand Journal of Marine and Freshwater Research. 39

Grant’s Guide to Fishes. Guide to the fishes of Australia. ISBN: 978-0-646-14106-0. Format: Hardback Pages: 880. Weight: 2.5kg. Size: 25cm long, 18cm wide and 5cm deep.

The Fishes of New Zea land – Edited by Clive Roberts, Andrew L Stewart, and Carl D Struthers.

The sweep