EDP Foz Tua: Fish – Complementary Studies [2011]

Study Extent

The study was carried out in 17 fixed stations covering the upper Tua (4 stations), Tinhela (2 stations), Tuela (1 station), Rabaçal (3 stations) and seven minor tributaries (Curros, Carvalhais, Macedo and Mentes, Rebousa, Milhais and Flagosa, 1 station each). Sampling was designed to sample areas of river with suitable habitat for Cobitis calderoni and Anguilla anguilla, covering the Tua river sub-basin. The maximum distance between stations was 5 km along the river Tua and its small tributaries up to the lower stretches of rivers Tuela and Rabaçal. Two additional stations located in these rivers were farther apart, but they were used because they contained suitable habitats for the species. Each station was sampled once in the summer of 2011 (23 to 30 of August).

Sampling

Samples were taken during the day by electro-fishing, by a team of two or three elements, using a portable device with a gasoline generator set (for safety reasons used as a fixed element), with pulsed direct current output (Hans Grassl ELT 60II-HI, 500-1000 V, 1300W), or a portable rechargeable battery pack for dorsal transport with continuous pulse output (Hans Grassl IG200 / 2C; 400-1000 V; <70 Hz). The fishing was carried in the opposite direction of the current current. In the course of the work, the welfare of the captured specimens was ensured by depositing them in plastic buckets with portable oxygenators, which were kept in shelters at cover of direct sun exposure. The usual safety measures for working with electrofishing were strictly followed. The individuals of all taxa caught were identified up to the species and counted. In the specific case of Cobitis calderoni, the total length (in mm) was measured with the aid of an ichthyometer. After these procedures, the native specimens were returned to their habitat in the vicinity of the capture sites with suitable conditions; at the request of the Institute of Conservation of Nature and Forestry (ICNF), exotic individuals were eliminated. A brief environmental characterization of each station was made “in situ”. The parameters used were: (a) abundance (n./ha) of exotic species present, (b) width (m) of the waterline, (c) altitude, (d) area (km2) of the basin, (e) distance (km) to the river springs, (f) slope (‰), (g) average yearly temperature (º), (h) average temperature of July (º), (i) precipitation (mm), (j) predominant substrate (mud, sand, gravel, grit, stones, blocks, rock), (k) depth (m) and (l) current velocity (m/s).

Quality Control

All fish was identified by experienced researchers with a deep knowledge of the local icthyofauna.

Method steps

1. To be completed

The taxonomic coverage of this dataset spans 1 phylum, 2 classes, 5 orders, 6 families and 10 species. All individuals were identified to the species level.

1. Animalia
   rank: kingdom
2. Chordata
   rank: phylum
3. Actinopterygii
   rank: class
4. Cephalaspidomorphi
   rank: class
5. Cypriniformes
   rank: order
6. Petromyzontiformes
   rank: order
7. Salmoniformes
   rank: order
8. Perciformes
   rank: order
9. Cyprinodontiformes
   rank: order
10. Cobitidae
    rank: family
11. Cyprinidae
    rank: family
12. Petromyzontidae
    rank: family
13. Salmonidae
    rank: family
14. Centrarchidae
    rank: family
15. Poeciliidae
    rank: family

The data was collected at 17 field stations along the valleys of rivers Tua, Tinhela, Tuela and Rabaçal (Northeast Portugal, Europe), within the municipalities of Alijó, Carrazeda de Ansiães, Murça, Mirandela, Macedo de Cavaleiros and Vinhais