Pacific porgy

Calamus brachysomus is a coastal fish of the family Sparidae, the porgies and seabreams, known in Peru as marotilla or sargo del norte ^[1]. It was described by Lockington in 1880 under the name Sparus brachysomus ^[2]. It is the only sparid of the tropical eastern Pacific and the Gulf of California ^[3]. It lives over shallow sand and gravel bottoms down to about 80 m depth ^[1]. It feeds mainly on molluscs and other bottom invertebrates ^[3]. In Peru it was regarded as an occasional visitor, but in 2025 its presence off Pisco, in Ica, was confirmed ^[1]. Its global category on the IUCN Red List is Least Concern ^[4].

In 10 specimens measured off Ica, maximum body depth averaged 39.8 % of standard length, the head 28.6 % and eye diameter 9.9 % ^[1]. In the same specimens, the pelvic fin averaged 32.5 % of standard length, and the anal and pectoral fins 27.6 % each ^[1].

The 10 Ica specimens measured between 16 and 18 cm total length and weighed between 79 and 121 g, so they were small fish ^[1]. The usual catch size lies between 15 and 46 cm, and the maximum recorded for the species is 61 cm total length ^[1]. FishBase also gives a maximum published weight of 2.3 kg ^[5]. The Peruvian authors identified them with the keys of Fischer and others (1995) and of Chirichigno and Vélez (1998) ^[1].

It is an eastern Pacific species, recorded from California (United States) and the Gulf of California (Mexico) to Tortugas Bay, and occasionally southwards to La Punta, in Callao, and Independencia Bay, in Peru ^[1]. FishBase summarises its range as lying between 29° north and 8° south latitude, and treats it as rare north of Baja California ^[5].

In Peru, 5 demersal resource surveys made between 1981 and 1987 detected it only between 3°20' S and 3°59' S, and not beyond 9° S ^[1]. Later, a study counted the species among the tropical fishes that reached northern Chile, between 18° S and 23° S, during the warm events of 1998 to 2000 ^[1].

Juveniles live in shallow water over mixed sand and rock bottoms; adults live over sand and along the edges of rocky reefs, down to about 80 m depth ^[3]. FishBase gives a range of 3 to 80 m and a usual depth of 3 to 18 m ^[5]. Off Ica, records from 2010 to 2014 were sporadic and isolated, increased from 2017, mostly between 2019 and 2024, and in 2025 reached the north of Independencia Bay ^[1].

It is an opportunistic predator of bottom invertebrates ^[3]. In 235 stomachs from the Gulf of California, 90 prey types were counted, of which 58 were molluscs; the rest were echinoderms (14), arthropods (13), chordates (2), one annelid, one sponge and algal remains ^[3]. The most important prey were bivalves of the genera Transennella, Argopecten, Anadara and Tivela, and the mussel Septifer zeteki ^[3]. The diet changed with the season, but not with sex or reproductive phase ^[3].

It breeds through most of the year. Among 265 specimens from Santa Rosalía, in the Gulf of California, females ready to spawn were present in 11 of the 13 months sampled, except in February and September ^[6]. The ovary develops asynchronously and spawning is in batches, with a peak of activity from May to July, when the sea surface is between 21 and 28 °C ^[6]. The sex ratio, 1.24 females per male, did not differ from 1 to 1 ^[6]. At another Mexican locality, Magdalena Bay, earlier studies reported that eggs hatched at temperatures of 20 to 26 °C ^[3].

From its diet, with a trophic level of 3.18, it is classed as a tertiary consumer, a link between high and low trophic levels ^[3]. Its trophic niche is narrow, with a Levin index of 0.31, and a few prey dominate the stomach contents ^[3].

On the gills of fish caught in the coastal zone of Puerto Pizarro, in Tumbes, lives the monogenean Haliotrematoides mediohamides, and Calamus brachysomus is its type host ^[7]. It is the third species of the family Dactylogyridae recorded on this fish in Peru ^[7].

Its presence off Pisco appears tied to warm conditions: after the 2023 Coastal El Niño, the authors suggest that warming favoured its arrival ^[1]. However, when the 2025 specimens were caught the surface temperature had already normalised, at 19.7 °C with an anomaly of -1.1 °C, which suggests the species may be shifting from visitor to permanent component ^[1].

Its global category on the IUCN Red List is Least Concern ^[4]. It is not the target of a directed fishery in the Gulf of California, but it is caught in large quantities as bycatch in multispecies fisheries in Mexico ^[3]. In the southern Gulf of California it is part of the incidental catch of shrimp trawling ^[1].

In Peru there is no evidence of a historical fishery directed at this species in Ica, but its greater availability is raising interest in catching and marketing it ^[1]. For that reason, the authors recommend continued monitoring of its distribution and of its possible effect on the region's marine ecosystems ^[1].

In Baja California Sur, in Mexico, it is an important commercial resource and is common in regional and national markets ^[3]. At Santa Rosalía it is taken with gillnets of 10 cm mesh, set between 10 and 35 m depth, from a fleet of 480 coastal boats of 6.7 to 10 m in length ^[3]. The growing interest in the species has also prompted studies of its feeding and reproduction with aquaculture in mind ^[3].

In Peru it is sold at the José Olaya Balandra artisanal fishing pier, in San Andrés, and in the local markets of Pisco, in Ica ^[1]. According to a field observer at the Laguna Grande cove, consulted in 2025, landings of the species have become continuous and constant in the artisanal fishing records ^[1].

The most recent records come from the coast of Ica. In May 2025, 10 specimens were caught with a purse seine, at 12 m depth over a sandy bottom, about 0.7 nautical miles from the La Poza fishing ground, north of Independencia Bay, and landed at the Laguna Grande pier, in Pisco ^[1]. Further north, a study published in 2022 redescribed a gill parasite from fish caught in 2018 and 2019 in the coastal zone of Puerto Pizarro, in Tumbes ^[7]. The sources record fishing catches, not observation sites for divers ^[1].