Brown Sea Cucumber

The brown sea cucumber are quite small organisms, with average body length and weight being 23 cm and 386 g, respectively. The largest samples have been recorded reaching up to 40 cm and weighing 830 g, although weight varies seasonally according to reproduction and the maturity stage. The species grows allometrically, meaning that increases with body length are also associated with increases in weight. Isostichopus fuscus is dioecious. Gonads can only be determined and sexed under a microscope. There is no apparent sexual dimorphism among individuals, unless gonads are ripe. When gonads are ripe, males are a white color, while females gonads are orange. The brown sea cucumber has an elongated body and can be described as having a soft or gelatinous texture.

This species is found in the Pacific Coast of Mexico, including the Gulf of California, and down through Central America to South America as far as the northern coast of Peru, as well as in eastern Pacific islands, including the Galápagos. They are found in shallow waters, roughly 0 to 40 m deep in rocky reefs, although 3 to 29 m are a preferred range. Additionally, reefs with sandy patches seem to be a preferred substrate. Within these depths, I. fuscus has been found to predominate areas where high amounts of Ulva sp. are located. The species tends to be more active at night as during the daytime they are cryptic and being active would make them more visible to predators.

Like other sea cucumber, I. fuscus is a deposit feeder, whose survival tends to increase with soft-substrates such as sand or clay. Recent studies suggest that a blend of seaweed species such as P. durvillaei and S. ecuadoreanum are an optimal diet, although they can survive off of other types of seaweed.

Spawning occurs in Isostichopus fuscus from July to September, with post-spawning gonads occurring in October. Gametogenesis was documented between January and July, with oogenesis occurring approximately one month before spermatogenesis. Peaks in reproduction followed by drastic declines have characterized I. fuscus as an episodic spawner, in which water temperature is thought to play a large role as a reproductive indicator.

The brown sea cucumber is a highly sought out commodity in many North and South American countries, including Mexico, Costa Rica and Ecuador. Sea cucumber fishing is also seen as the most important fishing activity in the Galápagos Islands. As it is such a common item in the fisheries of these countries, overfishing and overexploitation of the brown sea cucumber is a vast problem. Due to the endangered state of the brown sea cucumber, the Galápagos Marine Reserve and all major stakeholders took it upon themselves to monitor its population in the Galápagos twice a year between 1999 and 2003 in order to determine the impact of the fisheries and any possible solutions for it.