Table 3 List of environmental variables and management practices obtained from Nile tilapia production units between 2012 and 2013 in Yucatán State

Fish age (months)

2–4.5

2.5–6.0

Mean annual production (kg)

200–500

1,000–25,000

Water supply

<1 km

>1 km

Number of tanks on the farm

1–4

5–13

Tank capacity (m³)

4–6.5

12–16

Fish density per tank

950–4,500

5,000–10,000

Number of workers

1–2

4–9

Nearby communities

<1 km

>1 km

Fingerlings source

Campeche

Campeche – Tabasco

Type of tanks

Concrete – geomembrane

Concrete – geomembrane

Epidemiological outbreaks

Parasites, bacteria, fungi

Parasites, bacteria

Prophylactic treatments

No

Salt, Crustabay

Quarantine area

No

Yes

Vector presence

pigs, cattle, poultry, dogs and cats

Sometimes dogs

Guardhouse

No

Yes

Footbaths

No use

Yes

Tank cleaning

No disinfection

Virkon, chlorine

Bathroom

Latrine / No use

Bathroom

Disinfection of equipment

No disinfection

Virkon, chlorine

Warehouse

Galley / Lacking

Cement

Drug use

No

Antibiotics

Incineration of organisms

No

Burying and incineration

Education level of workers

No education

Elementary school, sometimes preparatory

Drainage

No drainage

With drainage

Communication

Roadless

With road

Livestock areas

Poultry and pigs

Poultry

Agricultural areas

Yes

Yes

Accumulation of garbage

Yes

No

Accumulation of dead animals

Yes

Sometimes

Water exchange rate

Monthly and fortnightly

Weekly and fortnightly

Water discharge treatment

No

Sometimes

Other land uses

Husbandry and livestock

Sometimes livestock

Nitrates (mg/l)

4.21–7.57

0.10–5.0

Nitrites (mg/l)

0.002–2.97

1.83–3.10

Ammonium (mg/l)

1.85–3.38

0.01–1.68

Salinity (ppt)

0.30–0.70

0.83–2.11

Dissolved oxygen (mg/l)

1.98–7.68

7.78–13.61

Conductivity (μS/cm)

1044–1698

1831–4364

Temperature (T °C)

23.10–31

28.92–32