Palm Ruff

Seriolella violacea is a bony fish of the family Centrolophidae, described by Guichenot in 1848 ^[1]. It forms schools near the coast and has been studied both in Chile and in Peru ^[2],[3].

In Peruvian restaurants a single trade name is used for this species and for another one, and what has been published about it from Peruvian waters deals mostly with its parasites and the food-safety questions they raise ^[4],[5]. Elsewhere in the region it is also being tested as a new farmed species, which is where much of what is known about its biology was measured ^[6],[7].

In Peru the species has been sampled from fish caught off Lima and Callao between 2012 and 2014 ^[3], and again off Lima, at about 12°09′ S, in a survey run between July 2017 and February 2018 ^[4].

The national checklist of monogeneans records it as a host for gill parasites collected off Lima, at 11°52′ S ^[8].

In Chile, according to the authors of a cytogenetic study, it forms schools near the coast, and adults are found on the continental shelf and also inside protected bays, along the whole northern coast of the country ^[2].

The species has 48 chromosomes, and its nuclear DNA content was estimated at 0.59 pg (C-value) from 6 fish, 4 males and 2 females, kept at a university marine culture laboratory in Coquimbo, Chile. Before that work the chromosomes of none of the 28 species of the family were known ^[2].

In tests on fish of 22 cm mean length at 15 °C, the critical swimming speed was about 80 cm/s (3.8 body lengths per second) and the most efficient speed was 50 cm/s (2.3 body lengths per second). At low speed the large pectoral fins, about 20% of body length, provided thrust and steering ^[6].

In larvae reared from hatching to 50 days, a stomach with its typical tissue organisation could be seen by 33 days, the gastric glands were visible at 35 days, and the specific activity of the digestive enzymes (except amylase) rose significantly between days 33 and 35 ^[9]. The first skull defect appeared at 5.7 mm total length, when the mouth opens, and the most frequent was a curved lower jaw, in 23.1% of larvae ^[7].

Rearing temperature changes growth a great deal: after 80 days, fish at 18 °C measured 55.5 mm and weighed 2.87 g, against 24.3 mm and 0.26 g at 14 °C, although survival was low in both cases (1.80% and 1.33%) ^[10].

It is a coastal pelagic fish with shoaling behaviour and a moderate metabolic rate compared with other pelagic species ^[6].

Its gills host a monogenean, Paraeurysorchis sarmientae (described in 1974 under another name, Pseudoeurysorchis sarmientoi); it was the first monogenean formally described in Peru ^[8].

It also hosts larvae of the nematode Anisakis pegreffii, a parasite whose adults live in marine mammals and whose fish hosts are paratenic ^[3]. Between 2012 and 2014, off Lima and Callao, 22.67% of 75 fish carried larvae, with a mean intensity of 9.88 larvae (range 1 to 48), significantly higher than in the other 3 species examined ^[3]. In the 2017-2018 survey, off Lima, 17.6% of 35 fish were infected, and all 10 larvae analysed genetically were Anisakis pegreffii; it was a new host record for that parasite ^[4].

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

Anisakis larvae can cause digestive disorders and allergic reactions in people who eat raw or undercooked fish, such as ceviche, although few human cases have been described in Peru and Chile ^[3].

In the fish of this species studied in 2017 and 2018 the larvae were only in the viscera; none were recorded in the musculature ^[4].

In 6 samples analysed in a study of seafood sold in Peru, total mercury averaged 60.44 ng/g wet weight (range 23.18 to 101.90), far below the 300 ng/g screening value of the United States environmental agency ^[5].

According to a parasitological study, in recent years the Peruvian fishery has sought to diversify towards resources such as this species and other fishes, which are well distributed along the coast and are among the most consumed seafood of the local population ^[4].

In Chile it is regarded as a candidate for aquaculture because of its fast growth and adaptability ^[2], and it has been proposed as a new farmed species for Chile and Peru ^[7].

A survey of 779 fishers at 39 landing sites in Peru and Chile, with catches estimated for 2023, linked gillnet meshes of 7.6 cm or more, and this species as a target, with the incidental capture of the Humboldt penguin; the authors conclude that mesh size seems to matter more than target species (5.4% of the variability on the main axis for species) ^[11].

The trade name shared by this species and Schedophilus haedrichi was the one most often mislabelled in the Peruvian restaurants sampled ^[5].