Brown Sea Cucumber

Isostichopus fuscus is a sea cucumber of the family Stichopodidae, described by Ludwig in 1875 under the name Stichopus fuscus ^[1]. In Peru it is called «pepino de mar de Galápagos» ^[2] or «pepino de Galápagos» ^[2], and it is the most commercially valuable holothurian of the tropical eastern Pacific ^[2]. Overfishing to supply Asian markets made its populations collapse, and in Peru it has almost disappeared ^[2].

Its body is almost cylindrical, arched on the back and flat underneath ^[3]. The back is dark brown and carries many sturdy, pointed yellow papillae scattered without forming rows; the underside is a lighter brown, with the tube feet grouped in dense bands ^[3]. The mouth sits on the underside, ringed by 20 yellow tentacles, and the anus, at the rear end, lacks teeth ^[3]. Under the microscope, the body wall holds table-shaped ossicles and C-shaped curved rods, but no rosettes ^[3].

Fresh, it weighs on average between 294 g in Ecuador and 497 g in Mexico, and its mean length runs from 20 cm in Ecuador to 24 cm in Mexico; once dried it turns greyish black and is usually 6 to 10 cm long ^[3]. In the northern Gulf of California, 2808 specimens averaged 21.4 cm, with a maximum of 41 cm and up to 1200 g in weight ^[4].

FAO's regional review places it from Baja California to mainland Ecuador, with the Galápagos, Socorro, Cocos and Revillagigedo islands, and notes that a 2005 study included Peru in its range, at the Lobos de Afuera Islands ^[5]. It occupies the coastal belt, from the shallow subtidal down to 39 m depth ^[5], although a 2017 article states that it reaches 61 m ^[4].

In the Galápagos it prefers rocky bottoms where the seaweed Ulva predominates ^[6], and in Baja California it usually lives on coral and rocky bottoms ^[5]. Occasionally it also turns up on sand or soft bottoms ^[4].

The sexes are separate, and males and females cannot be told apart by their appearance ^[6]. In the Galápagos it breeds all year round, regardless of water temperature, and in captivity it follows a lunar rhythm: it spawns between 1 and 4 days after the new moon, usually at night ^[6]. There it matures at 161 to 170.9 g drained wet weight; its larva feeds on plankton and, reared in the laboratory, settled between 22 and 27 days and reached 35 mm at 72 days ^[6].

In the northern Gulf of California, the northern edge of its range, the cycle is seasonal: gonads develop mainly from April to July, as the water warms, and spawning runs from June to November, peaking in August and September ^[4]. Of 553 gonads examined, 224 were female, 162 male, 157 undifferentiated and 10 hermaphrodite; the smallest reproductively active specimen measured 16 cm, and half of the population was sexually active at around 25 cm ^[4].

There are no growth estimates for the Galápagos; a preliminary calculation gave an asymptotic length of 36.118 cm and a growth coefficient K of 0.180 per year, and a later one obtained similar values, 29.108 cm and 0.243 ^[6]. At Bahías de Huatulco, in Mexico's southern Pacific, the von Bertalanffy equation gave an asymptotic length of 38.7 cm and a K of 0.4 ^[7]. The assembly of its genome, built from one specimen from Wolf Island, in the Galápagos, spans 898.4 megabases and has 23 chromosomes ^[8].

It is more active at night ^[5]. At Coronado Island, in Loreto Bay (Gulf of California), 70 transects of 100 m² surveyed by day and again by night in October 2008 gave an average of 1.943 animals per transect by day and 3.714 by night: by day it hides in crevices such as holes in the rock or coral bases, and at night it comes out to feed in open areas ^[9].

Its recruitment is irregular: in the Bolívar Channel, in the Galápagos, the indices stayed low between 1994 and mid-1999, the point at which a massive wave of juveniles arrived whose density reached its maximum in 2001 ^[10]. FAO's review links that pulse, probably, to the 1997-1998 El Niño, which favoured breeding, and to the productive La Niña that followed, which helped the juveniles grow ^[6].

At 3 sites in Bahías de Huatulco the mean density was 0.018 individuals per square metre, too low to sustain a fishery at any of them ^[7].

In October 2003 it was added to CITES Appendix III ^[6], at Ecuador's request ^[3], making it the first sea cucumber to appear in an appendix of that convention ^[6]. In mainland Ecuador fishing for it is banned outright; in the Galápagos it is managed with a total allowable catch, a minimum size of 20 cm fresh, no-take zones and a 2-month season ^[3].

In the Galápagos the fishery began in 1991, once it had been exhausted on the mainland; it was closed in 1992 and, when it reopened in 1994, the quota of 500000 individuals was overrun with catches of between 8 and 12 million ^[6]. A 1993 survey in eastern Fernandina gave 6.24 individuals per square metre, whereas in the Bolívar Channel densities from 1999 to 2007 ranged from 0.03 to 1.03 ^[6].

In Mexico it was fished heavily from 1988 to 1993; in 1994 fishing for it was banned outright, in 2002 it was allowed again subject to stock assessments, and in 2017 the species was listed under special protection ^[4].

In Peru the fishery began in the late 1980s and, once the species was depleted, the effort moved to other holothurians ^[5]; according to the 2008 FAO review, the country had no management measures for that fishery ^[5]. The management plan of the Mar Tropical de Grau National Reserve lists it among the highly threatened rocky-reef species ^[2] and prohibits taking it in the Arrecifes de Punta Sal ^[2], Cabo Blanco – El Ñuro ^[2] and Isla Foca sectors ^[2].

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

Protein-degrading enzymes extracted from its tentacles and partly purified were used to digest proteins from its own body wall; of the peptide fractions obtained, the most antioxidant came from the crude protein hydrolysate, at 0.92 µmol Trolox equivalents per mg of protein ^[11]. The authors see those peptides as possible ingredients for functional foods ^[11].

It is caught by hookah diving in semi-industrial fisheries; its rehydrated body wall is eaten in Asia, and its main markets are Hong Kong and the United States ^[3]. In China it is prized because its texture and flavour resemble those of Apostichopus japonicus, the favourite species there ^[6].

According to the CITES permits for the Galápagos catch, China received 98.5 % of exports in 2004 and 95.9 % in 2005, and Peru, through Lima, imported 36227 and 49494 animals in those years ^[6]. Part of the illegal catch from the Galápagos may be landed in mainland Ecuador, travel overland to Peru and be exported as a Peruvian product ^[6].

Its reproductive cycle has been completed in captivity and it has been reared in abandoned shrimp ponds in mainland Ecuador, which has stirred interest in restocking the Galápagos ^[6].

The 2026 management plan of the Mar Tropical de Grau National Reserve, drawing on a 2011 study, states that the species has almost disappeared in Peru and is recorded only rarely ^[2]. A FAO review notes that a 2005 study included the Lobos de Afuera Islands in its range ^[5]. In the reserve's Isla Foca sector, as in two other sectors, taking it is prohibited ^[2].