Shad

Ethmidium maculatum is a fish of the family Clupeidae, the herrings and sardines, in the order Clupeiformes ^[1]. It is the only species in its genus, lives in coastal waters of the southeast Pacific from northern Peru to Talcahuano, in Chile, and forms large schools ^[2]. In Peru it is called «machete» or «machuelo» and is taken by small-scale fishers, mostly with gillnets ^[3],[4]. Its global category on the IUCN Red List is Data Deficient ^[5].

Valenciennes described it in 1847 as Alausa maculata, from specimens taken at Valparaíso, Chile ^[2]. The genus Ethmidium was erected by Thompson in 1916, and its type species, described by Steindachner under another name, turned out to be the same fish as Valenciennes' ^[2]. In 1946 Hildebrand described Ethmidium chilcae from fish caught at Chincha Island, Callao and Pisco Bay, and many authors kept a Peruvian subspecies apart from the Chilean one; Whitehead, in 1970, doubted that body depth, pectoral fin length and scale shape could separate them, and the FAO catalogue concluded that more study was needed ^[2]. FAO gives it the English name «Pacific menhaden» ^[2].

The body is fairly deep and flattened from side to side, with a keel of scutes along the belly and a second row of scutes on the back, between the nape and the dorsal fin ^[2]. The upper jaw has a notch in the middle and carries no teeth, and the lower limb of the first gill arch bears 130 to 150 long, fine gill rakers ^[2]. The anal fin is short, with iii 12 to 15 rays, and starts well behind the end of the dorsal; the pelvic fins have i 6 rays, and the scales, 50 to 60 in a lateral row, have a toothed rear edge ^[2].

The easiest mark to see is the colour pattern: a dark spot behind the gill cover and up to 4 rows of upright oval spots along the flanks ^[2]. It grows to about 26 cm standard length and 35 cm total length ^[2]. In landings at La Libertad, fish of 16 to 29 cm were measured in 2010 and of 22 to 32 cm in 2016 ^[4],[3].

Similar species

• Sardinops sagax: Sardines of the genus Sardinops are the only other clupeids in the area with spots on the flanks, but their body is slimmer, the upper jaw has no notch, the back has no scutes and the gill cover bears radiating bony ridges ^[2].

The 1985 FAO catalogue gave its range as Puerto Pizarro, at 3°34' S in the Gulf of Guayaquil, to Callao and Pisco Bay in Peru, and the whole coast of Chile south to Talcahuano, at 36°40' S; it presumed the fish reached the Chilean border but had no records from that stretch ^[2]. It has since been studied in La Libertad, north of Callao ^[4],[3], and in Chancay Bay, in Lima ^[6], and a study cited by Atoche and Culquichicón measured its maturity at Callao and at Ilo ^[4].

It is a marine, pelagic, coastal fish that forms large schools ^[2]. In La Libertad in 2010, landings were larger in the south of the region and fell off towards the north, which the authors linked to its preference for cold water ^[4].

Among 1508 fish landed in La Libertad in 2010, females made up 57.4 %; length at first maturity was 18.12 cm in females and 20.50 cm in males, and the species was sexually active all year, with the heaviest spawning at the end of winter and the start of spring ^[4]. Length frequencies gave an asymptotic length of 30.83 cm for females and 29.07 cm for males, with fast growth during the first 2 years ^[4].

For Chile, the FAO catalogue stated that it spawns in spring, that its eggs are sticky and cling to sand, and that the larvae rise into the plankton on hatching ^[2]. Off Talcahuano, its eggs were collected with plankton nets: they measured 1.25 to 1.40 mm across, 1.30 mm on average in 47 eggs, and had no oil droplet ^[7]. Larvae hatched in the laboratory from those eggs measured 3.7 to 3.9 mm at hatching and finished absorbing their yolk at 6.4 to 6.5 mm ^[7].

It feeds by filtering phytoplankton, mainly diatoms, and zooplankton, especially copepods, and according to a synopsis cited by FAO it also takes small fishes and crustaceans ^[2]. In La Libertad in 2010, zooplankton made up most of the stomach contents, so the study classed it as a zooplankton feeder ^[4].

A 2016 study in the same region examined 362 stomachs with food and found 39 kinds of prey ^[3]. By count, pelagic diatoms were the most abundant item, at 55.5 %, but by wet biomass copepods made up 97.2 %, led by Oithona at 49.4 %, Calanus at 20.6 % and Paracalanus at 8.1 %; anchoveta eggs were among the minor prey ^[3]. There were no statistical differences in diet between size classes, from 21 to 32 cm, and the vacuity index showed less feeding activity from March to June than in the second half of the year ^[3].

Its global category on the IUCN Red List is Data Deficient ^[5].

In Peru, the minimum catch size for machete is 25 cm total length, with a maximum tolerance of 10 % juveniles, set by Ministerial Resolution No. 209-2001-PE ^[8]. In La Libertad in 2010, 52.9 % of the fish landed were below that size, and the authors called for management measures ^[4].

In 2024 the Ministry of Production authorised IMARPE to carry out an exploratory machete fishery along the Peruvian coast, first for 15 days and then for 45, because the institute reported that the lack of information was a major barrier to building management tools for this fishery ^[8].

Not medical advice. For a sting, a poisoning or an allergy, seek medical care.

In machete caught by small-scale fishers at Chancay between November 2022 and November 2023, every fish examined had microplastics in its gut ^[6]. The average was 10, 4 and 3.8 particles per fish in the 3 seasons sampled; across the whole study, which also covered Sarda chiliensis, black or blue fibres and fragments of 1 to 5 mm predominated, and chemical analysis identified polyethylene and polypropylene ^[6].

In Peru it is a small-scale fishery resource sold for human consumption ^[3],[6]. In La Libertad in 2009 it was the fish most landed by the inshore small-scale fleet, about 494 t and nearly 30 % of the total, but in 2010 its landings fell to 26779 kg, most of them at Puerto Morín and Salaverry ^[4]. It was caught mainly from small boats with gillnets of 2 to 3 inch mesh, and according to the authors it was not a targeted fishery but came up together with the mullet Mugil cephalus ^[4].

In 1983 a total of 6213 t was caught, 2100 t by Peru and 4113 t by Chile, with purse seines from both commercial and small-scale fleets; in 1978, 74.4 % of the catch went to fishmeal and oil ^[2].

It is a schooling fish known above all from fisheries. In 2010 it was landed at Pacasmayo, Malabrigo, Huanchaco, Salaverry and Puerto Morín, in La Libertad ^[4], and in 2016 it was sampled again at those same landing points ^[3]. In 2022 and 2023 it was brought in by small-scale fishers at the port of Chancay ^[6], and the first descriptions of the Peruvian form were based on fish from Chincha Island, Callao and Pisco Bay ^[2].