WALLACE RESOURCE LIBRARYWALLACE RESOURCE LIBRARYModule 05 – Natural Resource Use and Module 05 – Natural Resource Use and

SustainabilitySustainability

D03 – Quantifying the effect of fishing on D03 – Quantifying the effect of fishing on Amazonian fishAmazonian fish

WALLACE RESOURCE LIBRARYWALLACE RESOURCE LIBRARYModule 05 – Natural Resource Use and Module 05 – Natural Resource Use and

SustainabilitySustainability

D03 – Quantifying the effect of fishing on D03 – Quantifying the effect of fishing on Amazonian fishAmazonian fish

Amazonian fisheriesAmazonian fisheries

• The Amazon is home to the greatest richness of freshwater fish species in the world

• The Pacaya-Samiria Nature Reserve, Peru, was initially established to protect the paiche and other freshwater fish

• Fish stocks in the Samiria River are surveyed to assess impact of local fishing

Seasonality in water levelsSeasonality in water levels

• Aquatic ecosystem in Samiria River driven by large seasonal fluctuations in water levels

High water season (December to June):• Fish enter flooded forest to feed and

reproduce

Low water season (July to November):• Fish populations condensed in rivers,

channels and lakes

Threats to fisheriesThreats to fisheriesFisheries around the world are under threat from:• Climate change• Overfishing• Pollution• Habitat loss/destruction

• Samiria fishery is part of a protected reserve

• Only sustenance fishing (i.e. fishing for food not profit) by local Cocama people is allowed

• Quotas set to ensure fishing levels are sustainable

Survey methodologySurvey methodology

• Designed to replicate the fishing methods used by local people

• Gill nets set vertically in the water and left for one hour

• Fish caught are identified, measured and weighed

• Fish are then released back into the river

Monitoring fish populationsMonitoring fish populationsThese surveys are used to understand the health and stability of fish populations

•Abundance – measured as catch per unit effort– Can show trends in population numbers, or impacts of

extreme events

•Age structure of populations approximated from the frequency of different size classes– A population of shorter, younger fish is less stable

Research questionsResearch questions

1. How stable are the size distributions of the oscar (A. ocellatus) and white piranha (S. rhombeus) in the Samiria River, given constant fishing quotas and a drought in 2010?

1. Would you recommend adjusting the fishing quota for either species?

A. ocellatusA. ocellatus S.rhombeusS.rhombeus

Summary ConclusionsSummary Conclusions

0

5

10

15

20

10 14 18 22 26

Freq

uenc

y

Length (cm)

2008

0

5

10

15

10 14 18 22 26

Freq

uenc

y

Length (cm)

2009

0

5

10

15

20

10 14 18 22 26

Freq

uenc

y

Length (cm)

2010

0

5

10

15

20

10 14 18 22 26

Freq

uenc

y

Length (cm)

2011

0

10

20

30

10 14 18 22 26

Freq

uenc

y

Length (cm)

2012

• Since the 2010 drought, the dominant Since the 2010 drought, the dominant size class of the oscar population has size class of the oscar population has remained smallremained small• The fishing quota should be The fishing quota should be

lowered to enable the population lowered to enable the population to recoverto recover

• There was little effect of the drought There was little effect of the drought on the age structure of the white on the age structure of the white piranha populationpiranha population• The quotas for this species do not The quotas for this species do not

need adjustingneed adjusting