Pacific seahorse

Hippocampus ingens is a seahorse of the family Syngnathidae, described by Girard in 1858 ^[1]. In Peru it is called «caballito de mar» ^[2]. It is the only seahorse species on the Pacific coast of Latin America and a large species, up to 31 cm in height ^[3]. Its global category on the IUCN Red List is Vulnerable ^[4], and taking it from Peruvian waters has been banned since 2004 ^[5].

Its body is encased in bony rings, with a sturdy horse-like head covered in spines, a tube-shaped snout and, instead of a tail fin, a prehensile tail it uses to hold on to the substrate ^[6]. An adult of 185 mm caught in northern Chile had 11 trunk rings and 39 tail rings, 16 rays in the pectoral fin and 18 in the dorsal; it had a medium-sized coronet tilted backwards, a marked spine on the cheek and another above the eye, and was greyish yellow ^[6].

In 1760 dried specimens seized in northern Peru, the trunk averaged 11 rings and the tail had between 31 and 41 ^[7]. The male is recognised by its brood pouch; in a sample of 322 seized specimens, every male also showed a dark line along the belly, which the authors put forward as a supporting trait for sexing them ^[8].

On the Peruvian coast there is no other seahorse to confuse it with: a Peruvian study notes that it is the only species of the genus Hippocampus living along Peru's shoreline ^[8].

It ranges from San Diego, in the United States, to Pucusana, in Peru, including the Galapagos Islands ^[6]. Further south, in northern Chile, it has been recorded since the 1982-1983 El Niño, with finds in 1983, 1998 and 1999; in January 2017, a year without El Niño, 2 specimens came up in a trawl net at 4 m depth off Chañaral, which moves its known limit some 114 km further south ^[6].

In Latin America it is associated mainly with algae and rocky bottoms, and also with soft corals and reefs; fishers in Mexico found it between 1 and 55 m depth, with most catches between 20 and 35 m ^[3].

In Peru, according to IMARPE studies from 2007, the highest densities of the species are in the southern part of the Punta Sal sector ^[2].

It is the male that carries the brood pouch, the trait used to tell the sexes apart ^[8]. Under semi-controlled conditions, three mature wild-caught males, weighing 14.8 g, 24.5 g and 32.0 g, released 1598, 1703 and 1658 young, an average of 76.43 young per gram of male, with the water between 17 and 23 °C; the sex of the young could be told at 95 days of age, when they measured 6 to 7 cm ^[9].

The 322 specimens studied from a 2016 seizure from Tumbes, Piura and Lambayeque were classed as adults by the authors and measured 87 to 160 mm in total height; there were 1.21 females per male, a ratio that does not differ from 1:1, and males and females were of similar size ^[8]. In another lot seized the same year, of 1760 dehydrated animals, sizes ranged from 56 to 219 mm and weights from 0.53 to 5.37 g, and the authors conclude they were caught before reaching full size ^[7]. The largest known size for the species is 300 to 310 mm ^[6].

Its global category is Vulnerable ^[4]. The whole genus Hippocampus is on CITES Appendix II, so its trade has to be controlled ^[5].

In 2004 Peru's Ministry of Production banned taking it from Peruvian waters until studies show it can be harvested without endangering the species, and also made landing, transporting, processing and selling it punishable ^[5]. The rule relies on IMARPE's opinion, which judged the state of its populations uncertain and possibly critical and had found it scarce in biodiversity surveys along the coast; it adds that, being sedentary and slow, living at low densities and surviving very poorly in its early stages, it all but vanishes from areas where it is exploited and takes a long time to recover ^[5].

The ban has not stopped the trade: in 2019, 1053 kg were seized, a figure similar to the 1460 kg Peru exported in 2004, before the ban, and the two agencies that monitor its exports and imports report figures that do not match ^[10]. In 2016 lots of dried seahorses were seized in the north of the country, one of them from a vessel of Chinese origin ^[7],[8].

In the Mar Tropical de Grau National Reserve, the management plan describes it as highly threatened by extraction, above all in the Arrecifes de Punta Sal and Cabo Blanco – El Ñuro sectors, and notes that, despite the ban, trawling and extraction by divers for sale still affect its populations ^[2]. The plan bans taking it in the Arrecifes de Punta Sal sector ^[2], in Cabo Blanco – El Ñuro ^[2] and at Isla Foca ^[2].

In 2000, Peru had the largest domestic seahorse trade in South America, as curios and for traditional Chinese medicine, supplied by small-scale fishers and divers; the curio trade alone went through at least 23 buyers in 7 coastal localities, who together handled between 1300 and 4100 seahorses a year (5 to 15 kg), and a soup with seahorses cost 10 dollars a bowl ^[3].

Seahorses were also exported, at least to Canada, Hong Kong and mainland China: fishers in Tumbes and Piura and divers in Pisco said they had sold seahorses to middlemen since 1995-1997, and exporters were estimated to have access to no less than 415 kg of dried seahorses a year; Hong Kong recorded imports from Peru of 1838 kg in 2003 and 2079 kg in 2004, the largest amounts logged up to then ^[3].

According to IMARPE studies from 2007 cited in the management plan of the Mar Tropical de Grau National Reserve, Peru's highest densities are in the southern part of the Punta Sal sector ^[2]. Taking it is banned in that sector of the reserve ^[2]. The seahorses seized in 2016 and later studied came from the coast of Tumbes, Piura and Lambayeque ^[8].