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ICAR AICE-JRF/SRF Statistical Ecology, Environmental & Fisheries Statistics: practice questions

ICAR AICE-JRF/SRF - Agricultural Statistics, Computer Application, Bioinformatics (PhD admission and fellowship) · India · National Testing Agency for ICAR

Original practice questions written to the published syllabus · not past papers
10worked here, free
42written to this exam in this subject
10syllabus units

What this subject covers

Counting what cannot be counted directly: capture-recapture and distance sampling, quadrat and line-transect methods, diversity indices and species-abundance models, fish stock assessment, forest inventory sampling and environmental monitoring designs.

In the exams: AICE-JRF Ag Stat Unit 5 'livestock and fishery statistics' (present); ICAR MSc/PhD elective; light in national exams

Where the 42 questions fall

How our questions for ICAR AICE-JRF/SRF spread across the units of Statistical Ecology, Environmental & Fisheries Statistics. Difficulty: 7 easy, 23 medium, 12 hard.

Capture-recapture: Lincoln-Petersen and open-population models5
Diversity indices: Shannon, Simpson and species richness estimators5
Extreme value analysis of rainfall and floods5
Spatial patterns: random, clumped and regular; dispersion indices4
Quadrat, line-transect and distance sampling4
Population dynamics models: logistic and Leslie matrix4
Fish stock assessment: growth (von Bertalanffy), mortality and yield-per-recruit4
Forest inventory: plot sampling, point sampling and volume estimation4
Environmental monitoring designs and trend detection4
Species-abundance and species-area models3

10 practice questions, worked

Choose an answer, then open the working. Each explanation says why the right answer is right and why the others are not.

1 · Spatial patterns: random, clumped and regular; dispersion indices · hard

The Clark–Evans nearest-neighbour ratio for a perfectly regular hexagonal pattern is about:

  1. 2.15
  2. 1.00
  3. 0.00
  4. 0.50
Answer and working

A. 2.15

1 indicates randomness, values below 1 clumping, and about 2.15 the maximum regularity.

Further reading: Krebs, Ecological Methodology (1999); Buckland et al., Introduction to Distance Sampling (2001); Magurran, Measuring Biological Diversity (2004); Sparre and Venema, FAO Fisheries Technical Paper 306/1 (1998); Coles, Statistical Modeling of Extreme Values (2001)

2 · Quadrat, line-transect and distance sampling · medium

The critical assumption of conventional distance sampling is that:

  1. Objects on the line are always seen
  2. All objects within the whole strip are detected
  3. Detection does not depend on distance
  4. Objects move towards the observer
Answer and working

A. Objects on the line are always seen

g(0) = 1; detection is allowed to fall with distance.

Further reading: Krebs, Ecological Methodology (1999); Buckland et al., Introduction to Distance Sampling (2001); Magurran, Measuring Biological Diversity (2004); Sparre and Venema, FAO Fisheries Technical Paper 306/1 (1998); Coles, Statistical Modeling of Extreme Values (2001)

3 · Capture-recapture: Lincoln-Petersen and open-population models · medium

If marked animals become trap-shy, the Lincoln–Petersen estimate will tend to be:

  1. Too low
  2. Unbiased
  3. Zero
  4. Too high
Answer and working

D. Too high

Fewer recaptures (smaller R) inflate MC/R.

Further reading: Krebs, Ecological Methodology (1999); Buckland et al., Introduction to Distance Sampling (2001); Magurran, Measuring Biological Diversity (2004); Sparre and Venema, FAO Fisheries Technical Paper 306/1 (1998); Coles, Statistical Modeling of Extreme Values (2001)

4 · Capture-recapture: Lincoln-Petersen and open-population models · medium

In closed-population capture–recapture model Mh, capture probability varies:

  1. Among individuals
  2. With time only
  3. With behavioural response only
  4. Not at all
Answer and working

A. Among individuals

Mt varies by occasion and Mb by behaviour; M₀ is constant.

Further reading: Krebs, Ecological Methodology (1999); Buckland et al., Introduction to Distance Sampling (2001); Magurran, Measuring Biological Diversity (2004); Sparre and Venema, FAO Fisheries Technical Paper 306/1 (1998); Coles, Statistical Modeling of Extreme Values (2001)

5 · Diversity indices: Shannon, Simpson and species richness estimators · medium

Many singletons in a sample of a community suggest that:

  1. The community is fully sampled
  2. Diversity is zero
  3. Simpson's index is exactly 1
  4. Many species remain undetected
Answer and working

D. Many species remain undetected

Chao estimators use singletons to estimate unseen species.

Further reading: Krebs, Ecological Methodology (1999); Buckland et al., Introduction to Distance Sampling (2001); Magurran, Measuring Biological Diversity (2004); Sparre and Venema, FAO Fisheries Technical Paper 306/1 (1998); Coles, Statistical Modeling of Extreme Values (2001)

6 · Species-abundance and species-area models · hard

Why do species–area extrapolations tend to overestimate immediate extinctions after habitat loss?

  1. Species–area curves always underestimate richness
  2. Islands have no species
  3. Habitat loss increases species
  4. Species persist in the matrix; losses lag
Answer and working

D. Species persist in the matrix; losses lag

The matrix is not an ocean, and extinction debts take time.

Further reading: Krebs, Ecological Methodology (1999); Buckland et al., Introduction to Distance Sampling (2001); Magurran, Measuring Biological Diversity (2004); Sparre and Venema, FAO Fisheries Technical Paper 306/1 (1998); Coles, Statistical Modeling of Extreme Values (2001)

7 · Fish stock assessment: growth (von Bertalanffy), mortality and yield-per-recruit · medium

In a Ford–Walford plot of Lₜ₊₁ against Lₜ, the slope equals:

  1. K
  2. L∞ (asymptote)
  3. t₀
  4. e^(−K)
Answer and working

D. e^(−K)

Where the line crosses Lₜ₊₁ = Lₜ gives L∞.

Further reading: Krebs, Ecological Methodology (1999); Buckland et al., Introduction to Distance Sampling (2001); Magurran, Measuring Biological Diversity (2004); Sparre and Venema, FAO Fisheries Technical Paper 306/1 (1998); Coles, Statistical Modeling of Extreme Values (2001)

8 · Forest inventory: plot sampling, point sampling and volume estimation · medium

Huber's formula estimates log volume as:

  1. Mid-length area times length
  2. Mean of the two end areas times length
  3. Area of the large end times length
  4. Length cubed
Answer and working

A. Mid-length area times length

Smalian's formula averages the end areas.

Further reading: Krebs, Ecological Methodology (1999); Buckland et al., Introduction to Distance Sampling (2001); Magurran, Measuring Biological Diversity (2004); Sparre and Venema, FAO Fisheries Technical Paper 306/1 (1998); Coles, Statistical Modeling of Extreme Values (2001)

9 · Extreme value analysis of rainfall and floods · medium

The Weibull plotting position assigns the m-th largest of n annual maxima an exceedance probability of:

  1. m/(n + 1)
  2. m/n
  3. (m − 1)/n
  4. 1/m
Answer and working

A. m/(n + 1)

It avoids assigning probability 0 or 1 to observed extremes.

Further reading: Krebs, Ecological Methodology (1999); Buckland et al., Introduction to Distance Sampling (2001); Magurran, Measuring Biological Diversity (2004); Sparre and Venema, FAO Fisheries Technical Paper 306/1 (1998); Coles, Statistical Modeling of Extreme Values (2001)

10 · Extreme value analysis of rainfall and floods · hard

Why are 500-year return levels estimated from a 30-year record very uncertain?

  1. They extrapolate far beyond the data
  2. Return periods cannot exceed 100 years
  3. Annual maxima are always normal
  4. Records of 30 years are too long
Answer and working

A. They extrapolate far beyond the data

Confidence intervals widen rapidly beyond the record length; regional analysis helps.

Further reading: Krebs, Ecological Methodology (1999); Buckland et al., Introduction to Distance Sampling (2001); Magurran, Measuring Biological Diversity (2004); Sparre and Venema, FAO Fisheries Technical Paper 306/1 (1998); Coles, Statistical Modeling of Extreme Values (2001)

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Statistical Ecology, Environmental & Fisheries StatisticsThe full study manual, free ICAR AICE-JRF/SRFFormat, sections and how it has changed

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