Cancer porteri

Cancer porteri is a crab of the family Cancridae, order Decapoda ^[1]. It lives in the south-eastern Pacific from the Lobos de Afuera islands, in Peru, to Chile ^[2]. In Chile it supports an artisanal fishery, with 446 tonnes landed in 2023 ^[3].

The Peruvian catalogue credits the name Cancer porteri to Rathbun, 1930 ^[2]. It also lists Cancer longipes Bell, 1835, a name already occupied by Cancer longipes Linnaeus, 1758 ^[2].

The catalogue of decapod crustaceans of Peru gives the colour of the species as cream and white, mottled with purple ^[2]. It examined 5 males of 34.8 to 48.1 mm carapace length and 3 females of 31.9 to 41.7 mm, collected at a single locality in Callao ^[2].

Its walking legs are slender, so in Chile only the claws are used as food ^[3].

Similar species

• Cancer plebejus: Cancer plebejus is reddish brown, deep red or orange-red, with conspicuous white spots on each side of the midline of the carapace, arranged in a half-moon ^[2].
• Metacarcinus edwardsii: Metacarcinus edwardsii is reddish brown above and yellow mottled with red below ^[2].
• Romaleon polyodon: Romaleon polyodon is reddish brown above, sometimes with yellow flecks in young animals, and red mottled with yellow below ^[2].

Its range runs from the Lobos de Afuera islands, in Peru (6.9° S), to Mocha Island, in Chile (38.4° S) ^[3]. The Peruvian catalogue records it from Lobos de Afuera to Talcahuano, in Chile, and names San Lorenzo Island, the Palomino islets and the bays of Independencia, San Juan and San Nicolás as Peruvian localities ^[2].

It lives from the intertidal zone down to about 350 m depth according to the Peruvian catalogue ^[2]; another source gives a range of 0 to 375 m and notes a preference for muddy bottoms ^[3].

Its southern limit is consistent with the outcome of larvae reared in the laboratory at 10, 13, 16 and 19 °C: at 10 °C all died in zoea III and at 13 °C all died in zoea V, in line with a southern limit near 38° S ^[4].

In Valparaíso, females reach sexual maturity at a cephalothorax width of 92 mm, which corresponds to an age of 2.3 years in females and 2.5 years in males ^[3]. Between 288750 and 323130 eggs have been estimated for females of 61.3 to 64.9 mm cephalothorax length, and up to 740920 eggs for females of 83.8 to 118.2 mm ^[3].

Its larval development had only been described up to the first zoea; other cancrid crabs in Chile have a planktonic larval phase of more than 2 months ^[3]. Males usually form harems of 3 to 5 females and guard them ^[3].

The nemertean worm Carcinonemertes camanchaco lives in the egg masses of egg-bearing females ^[5]. In November 2020 it was found in 24 % of 21 egg-bearing females from Valparaíso, with a mean of 2.6 worms per egg mass, and in none of 48 females without eggs from Iquique ^[5].

In Tongoy Bay, in northern Chile, a study used this species as a top predator to compare the cascade of effects expected in a soft-bottom community with the predictions of ecological models ^[6]. It is also part of the bycatch of demersal crustacean fisheries off north-central and south-central Chile ^[3].

In Chile, crab fisheries are governed by general measures such as a minimum landing size and a ban on taking egg-bearing females ^[3]. A 2021 study reported that landings of this species fell from 667 tonnes in 2014 to 2.62 tonnes in 2019 and that specific management measures were applied ^[5]; in 2023, 446 tonnes were landed ^[3].

A genetic study with samples from 161 individuals (127 after data filtering), from 2014-2015 and 2023-2024, suggests a single large population over the stretch from 23°37′ S to 36°36′ S, with high gene flow ^[3]. Its authors note that, without demographic studies, it is hard to tell whether the species is vulnerable to local demographic fluctuations and fishing pressure ^[3].

In Chile it is an artisanal fishery resource taken between Valparaíso (32°02′ S) and Biobío (36°49′ S); it accounted for 17 % of brachyuran crab landings between 2009 and 2019 ^[3]. The specimens of the genetic study were obtained by fishers using traps ^[3].

Only the claws are eaten, so it is common to remove them and return the animal to the sea; this practice could affect reproduction, because males guard the females of their harem ^[3].

In Peru, the specimens in the catalogue were collected on 9 January 1993 at Cantolao, La Punta (Callao), among fish and crustacean debris left by the sea ^[2]. The catalogue, published in 2012, also names San Lorenzo Island, the Palomino islets and the bays of Independencia, San Juan and San Nicolás as Peruvian localities ^[2].