Merluccius peruanus

Merluccius peruanus is the hake of northern Peru. The FAO hake catalogue treats it as the Peruvian population of Merluccius gayi, with the rank of subspecies and with reservations ^[1], while the taxonomic register WoRMS accepts it as a species in its own right ^[2]. It lives near the bottom of the continental shelf, with its largest concentration between 3° and 10°S ^[3].

It feeds mostly on fish, among them other hake and the Peruvian anchovy ^[4]. It is the target species of the main bottom trawl fishery of northern Peru, which began in the 1950s ^[3]. The FAO catalogue, which gives catches of Merluccius gayi without separating the two populations, cites for Peru more than 300,000 t in 1978 and just over 5000 t in 1983 ^[1].

In 1954 Ginsburg described the Peruvian population as the subspecies Merluccius gayi peruanus, with specimens from Paita and Callao as its type locality ^[1]. The name Merluccius peruanus, at species rank, is the one WoRMS accepts, within the family Merlucciidae and the order Gadiformes ^[2].

The FAO catalogue lists the local names «merluza», «huaycuya», «merlango», «peje palo», «pescada» and «pescadilla» for Peru ^[1].

It is an elongated fish with a blackish-grey back, especially on the head and fins, a horizontal orange stripe halfway up the flanks and a whitish belly ^[1]. The head measures between 26 and 33.5 % of the standard length, and there are no scales on the nasal membrane, the lacrimal bone or the lower cheek ^[1].

For the Peruvian population the catalogue gives 10 to 13 rays in the first dorsal fin, 36 to 40 in the second and 36 to 39 in the anal fin, with 17 to 23 gill rakers on the first arch and 48 to 53 vertebrae ^[1]. The tips of the pectoral fins always pass the start of the anal fin, and the gill rakers and their base carry small black pigment spots ^[1].

The Chilean population, separated from the Peruvian one by some 1300 km, differs little in those counts, which is why the FAO accepts the two subspecies with reservations; according to the catalogue, the counts of the Peruvian one resemble those of Merluccius angustimanus more than those of the Chilean one ^[1].

Similar species

• Merluccius angustimanus: The Panama hake, described from the Gulf of Panama and ranging from Colombia to the Gulf of California, has 13 to 18 gill rakers on the first arch, against 17 to 23 in the Peruvian population, and 49 to 52 vertebrae against 48 to 53 ^[1],[1]. The counts overlap, so they do not separate the two with certainty, and the FAO itself notes that the counts of the Peruvian one resemble those of this species ^[1].

According to the FAO catalogue, the Peruvian population ranges from Punta Pariñas (4°40'S) to Tambo de Mora (13°56'S), with the largest concentrations between 6° and 9°S ^[1]. A paper from the Instituto del Mar del Perú places it under normal conditions between 0°30'S and 10°S, with its core between 3° and 10°S and its greatest density at depths of 100 to 200 m ^[3].

Its habitat depends on the southern branch of the Cromwell Current, which flows from north to south between 100 and 500 m depth, and the species tolerates temperatures of 10° to 22 °C ^[1]. With El Niño it shifts south: in 1997-1998 it reached 18°S, and in 2016 and 2017 specimens were caught off Quilca, Arequipa, at 16°42'S; in July 2017 a gillnet set at about 45 m depth brought up 56 hake of 26 to 34 cm ^[3].

According to the FAO catalogue, males mature at 27.3 cm and females at 29.9 cm; spawning is fractional and takes place all year, peaking in August and September, with a smaller second peak in summer ^[1]. A female of 40 to 70 cm produces 78,000 to 174,000 oocytes ^[1]. The mean size in the areas of greatest concentration is 40 cm, at about 4 years, and large specimens are usually found south of 6°S ^[1].

Of the 56 specimens from Arequipa in 2017, 89.36 % of the females were mature, and the authors compare their size structure with that of age group 2 of the northern population ^[3]. The 2008 IMARPE assessment used a natural mortality of 0.38 per year ^[5]. In 2004-2007 the population in the fishery consisted mostly of hake aged 1 to 3 years ^[5].

Orrego and Mendo examined 2836 stomachs of hake of 24 to 73 cm, taken aboard industrial trawlers in northern Peru between 1995 and 1997: fish made up 87 % of the ingested mass, cephalopods 10.4 % and crustaceans 2.6 % ^[4]. Within the fish, hake itself ranked first (40.6 %), followed by the family Engraulidae (24.1 %), with the Peruvian anchovy clearly dominant ^[4]. According to the authors, in 1997 the diet became more varied, which they attribute to El Niño ^[4].

The FAO catalogue adds that individuals under 30 cm eat mostly crustaceans, particularly euphausiids, and larger ones eat sardines and other fish; from 50 cm cannibalism is common and accounts for 30 % of the species' natural mortality ^[1]. When the hake moves south, its consumption of anchovy rises ^[1].

The oldest fishery data show heavy exploitation: according to the FAO catalogue, coastal and distant-water trawler fleets fished it from 1970 and exported almost the whole catch, until the fishery collapsed in 1980 ^[1]. The maximum total catch of Merluccius gayi reported to the FAO was in 1978, at more than 380,000 t, with more than 300,000 t Peruvian, and in 1983 the Peruvian catch fell to just over 5000 t ^[1].

An IMARPE assessment published in 2009 describes a moratorium in force from September 2002 to May 2004, which cut the catch to a minimum, and a fishery that resumed with individual non-transferable quotas and observers aboard the whole industrial fleet ^[5]. Between 2004 and 2007 the mean vulnerable biomass was about 64,000 t, of which roughly 67 % was reproductive biomass ^[5]. The authors concluded that, with the fishing pattern of those years, the spawning biomass could not be expected to grow, and calculated that lowering fishing mortality to 0.48 per year would make it grow 33 % a year, to 0.26 per year 53 % and a total closure 84 % ^[5]. These data are from 2008 and do not describe the current state of the resource ^[5].

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

Of 62 hake bought at the Ventanilla fishing terminal, Callao, in January and February 2014, 59.67 % had cysts of the myxosporean Kudoa peruviana in the muscle, with a mean of 241.62 cysts per infected fish ^[6]. The authors point out that Kudoa infections in marine fish are known to damage muscle tissue ^[6].

Another study, of hake from that same terminal and those months, identified 15 parasite species, among them the nematode Anisakis simplex and the cestode Diphyllobothrium pacificum ^[7]. Soto bought 150 hake at the Terminal Pesquero Grau, in Ayacucho, between July and December 2023: 8 % carried Anisakis larvae, 2 % of Anisakis simplex and 6 % of Anisakis physeteris, always in the peritoneal cavity ^[8].

Hake is the target species of the main bottom trawl fishery of northern Peru, which started in the 1950s and which, according to IMARPE authors, brings in foreign exchange and jobs and weighs on the country's fishing production chain ^[3]. Chero and colleagues describe it as the most abundant and economically valuable species of the bottom trawl fishery ^[7].

According to the FAO catalogue, in the period of greatest activity almost the whole Peruvian catch was exported, and South Pacific hake is preferably marketed frozen ^[1]. The 2008 IMARPE assessment states that when fishing resumed in May 2004, individual non-transferable quotas and observers aboard the whole industrial fleet were applied ^[5].