Río San José, Horquetas, Sarapiquí, Costa Rica

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Costa Rica, Heredia, Horquetas / Sarapiquí / Heredia

The San José River is part of the Sarapiquí River basin in the northern part of Costa Rica. This basin has an extension of 2.025km².

This area is very calm, here you can see the interactions of flora and fauna with humans. There are clear, clean waters that people use for recreation. In this sector you can find many fish interactions and especially the cichlids which are my favorites.

Submitted by
Andrés Cordero Porras
Approved by
Juan M. Artigas Azas, Jairo Arroyave & Michael Köck
10.3182783, -83.8910141
Geographical region
Central America
Drainage Basin
Río San Juan
River catchment
Braulio Carrillo National Park in Heredia
Water body type
Water body name
San José
Water body part
Water body course
Middle course
Water body: tributary of
Tributary name
Río Sarapiquí

Videos above and below water

Water Chemistry

Water information

Water type
Fresh water
Water color
Clear water
Water transparency
Concentration of sediments
Water temperature
25 °C
Water flow/curent

Chemical parameters

534 mg/l
Dissolved Oxygen
9 %

Substrate in nature

Stone form
Submerged terrestrial vegetation

Aquatic Biotope

Date of collecting
January, 2023
Collecting area
Middle waters
Water depth
Air temperature
28 °C
Full sun


Affected by human activity
Affected by human activity
Surrounding area

This area is located in one of the strongest agricultural sectors in Costa Rica. It is a site that is surrounded by roads and large banana farms. Despite this, it is a site with a lot of biodiversity. On the banks of the river, green iguanas and howler monkeys are easily found.

This ecosystem consists of pure round stones, there are no plants in it due to strong currents, and at any time of the year there are floods that drag everything in their path. For these reasons, the fish found here are adapted to hide in small crevices between the rocks and hold on to strong currents.

This territory is characterized by its high temperatures, which range from 20.3-30.3°C. It is a place in Costa Rica that rains all year round and has an annual rainfall of 3.500-4.000mm per year. The climate of this place is known as very Humid, very hot. The life zones around this point are very humid tropical forests.

Underwater landscape

The watercourses in the area are strong and do not have aquatic plants. But there are a lot of plants on the river bank, all their roots create a lot of shelters for aquatic creatures. There are also many trees that have their roots in the river.

In the water there are stones completely covered with algae, river sand, sunken pieces of wood and fallen leaves in the crevices of rock structures. The clear water shows all the colors of the fishes with the sun shining without any shadow. Due to the lack of shade, the water flowing down to the river bank is very hot and does not allow anything to live in these places. But the little ponds that get shade are full of tadpoles.


  • Neetroplus nematopus (Cichlidae)
  • Amatitlania siquia (Cichlidae)
  • Astyanax aeneus (Characidae)
  • Tomocichla tuba (Cichlidae)
  • Amatitlania septemfasciata (Cichlidae)
  • Alfaro cultratus (Poeciliidae)
Threats to ecology

Water is a super important resource for life. This site is full of diversity, has a lot of reptiles, amphibians, mammals and birds. They all meet to feed and hydrate near the river.

For these same reasons, wildlife crossings have been created in this same spot. During the visit, howler monkeys were observed using them and crossing from one side of the river to the other.

Despite this great importance for wildlife and for humans, the water resource has been degraded by human progress. Pollution, erosion from monocultures, and poor solid waste management threaten this ecosystem.

Another big problem is that this river is used for spearfishing for human consumption. The number of species they extract in each fishing trip is incomprehensible. This causes a great impact on the ichthyofauna populations of the place. They also use chemicals to catch shrimp for consumption. This ends up poisoning the river and is a huge threat to this beautiful ecosystem.

Riparian zone

Trees near the aquatic habitat
Few - Erythrina berteroana (Fabaceae)
Trees near the aquatic habitat
Few - Cascabela ovata (Apocynaceae)
Trees near the aquatic habitat
Few - Zygia longifolia (Fabaceae)

Comment by the expert

Michael Köck: The description of the habitat is clear and I guess everyone has a clear picture of what to expect. The threats are understandably described. A mistake with the GH in the water parameters happened, probably caused by translation, but the cited literature is well chosen.

Juan M. Artigas Azas: It has been 21 years since I last was at this beautiful river wanting to go back and the video has brought to me a beautiful reminder, thank you! I need to say however that the video is a little distressing since the videographer apparently approached breeding Tomocichla tuba very much, causing the pair to lose coordination and with this the Astyanax to eat most (the whole?) spawn. One should always be respectful and never approach so much as to allow this to happen. I found the list of the fish short, perhaps just a reflection of a description of a very specific place, but shouldn’t at least Poecilia gilli be present? As a recommendation, the wonderful book by William Bussing “Peces de las aguas continentales de Costa Rica” would be a great source of information about the fish fauna of this wonderful place — and all of Costa Rica.

Jairo Arroyave: As pointed out by Juan Miguel, species list seems a bit short, although consistent with the actual BIN based on the video. Bibliography is perhaps missing the most important resource of this kind: Bussing’s book in the freshwater fishes of Costa Rica. Other than that, and the stress incurred on the fishes (as mentioned by Juan Miguel) the documentation of both surface and underwater habitat is superb.