Survey Methods

2025-05-12
Elkhorn Slough RTEP

One thing to remember is to talk to the animals. If you do, they will talk back to you. But if you don’t talk to them, they won’t talk back to you, then you won’t understand. And when you don’t understand, you will fear, and when you fear, you will destroy the animals, and if you destroy the animals you will destroy yourself

Chief Dan George | Tseil-Waututh Nation (1899-1981)

Overview

Snorkeling

  • Visual Encounter Surveys (VES):
    • Egg Masses (EM)
    • Tadpoles
    • Adults
  • Equipment
  • Conditions vs. Survey Techniques
  • Other Methods

Overview

There is a balance in how we document, catalog, and observe wildlife. Nature is messy and it can be difficult to detail the pieces of interest. But consistent methods provide a framework we can use to compare and contrast our observations.

What is the objective?

Long-term monitoring of reproduction

Restoration sites:

  • Recolonization
  • Persistence of restored habitat

Oviposition relative to flow and temperature

Development of larvae at different thermal regimes

Resources

  • PARC 2013 Gabrielle J. Graeter, Kurt A. Buhlmann, Lucas R. Wilkinson, J. Whitfield Gibbons

  • Smithsonian 1994 Heyer, W. R., M. D. Donnelly, R. W. McDiarmid, L. C. Hayek, M. S. Foster

References

Definitions

Measuring and Monitoring Biological Diversity: Standard Methods for Amphibians. 1994. Eds, Heyer et al.

  • Relative abundance: proportional representation of species in a sample
  • Inventory: study of a specific area, site, or habitat to determine the number of species present (i.e. species richness)
  • Monitoring: study of the abundance of individuals in one or more populations of a species at a site through time
  • Mark-recapture techniques: methods for determining population size that involve capturing, marking, and releasing animals, and subsequently recapturing or re-sighting them one or more times.
  • Visual Encounter Survey (VES): estimate the diversity (number of. different species) and abundance (number of different individuals) of animals at a particular location

Definitions

Life Cycle & Survey Timing

Timing of Surveys

  • Monitor local conditions
    • River stage/discharge (CDEC, USGS)
    • Storm forecasts
    • Water and air temperatures
  • Compare with activity at reference sites

Visual
Ecounter
Surveys
(VES)

VES

  • Search Area: need GPS of begin/end
  • Habitat:
    • Wetted width / bankfull width
    • Avg depth / max depth
    • turbidity / sedimentation / embeddedness
    • canopy cover
    • geomorphic type (run / riffle / pool)
    • invasives | disturbance
  • Conditions: survey conditions important
    • sunny/windy/warm/cold
    • flow/water quality at site
    • air/water temp at site
  • Search Duration: crucial to quantify effort
    • Obs times provides information on time-to-detection

Important to check shoreline

and edgewater…

VES Snorkeling

  • Snorkeling highly recommended/mandatory for spring egg mass surveys
  • Suitable for monitoring the abundance & distribution
  • tandem teams ideal for paired survey

VES Snorkeling

  • Egg masses can be very cryptic
  • Snorkeling has been found to be highly effective
  • Site conditions can greatly impact where egg masses are located (didymo)

Survey Gear

  • Polarized glasses
  • Binoculars
  • Ruler/calipers
  • Temperature / WQ probe
  • Measuring tape
  • Depth rod/stick

Egg Masses

Observational Data: Oviposition

Stream Habitat – Physical Attributes:

  • Water Temperature | Velocity
  • Total Depth | Egg mass depth
  • Distance to Shore | Geomorphic unit

Attachment Substrate:

  • Pebble (33-64 mm) | Cobble (65-256 mm) | Boulder (>256 mm)
  • Bedrock | Woody material | Riparian vegetation
  • Orientation (upstream / downstream / shore / under / top)

Egg Stage (Gosner)

  • Early | Bean | Tail | Hatching

Tracking Fate of Eggs

  • Multiple visits are important during breeding period
  • Knowing if eggs are going to be stranded or scoured
  • Track development and dispersal

Tracking Fate of Eggs

  • Multiple visits are important during breeding period
  • Knowing if eggs are going to be stranded or scoured
  • Track development and dispersal

from S. Kupferberg, SF Eel

cumulative frequency curves from the SF Eel to show that a well timed survey 3-4 weeks after egg laying starts could capture about 90% of the egg laying. In other words at a site with cool temperatures most clutches would not have completely hatched and dispersed, and could still be counted.

Larvae

Observational Data: Larvae

Developmental Stage

  • Gosner or other
  • Condition
  • Algae observations
  • Predators?

Cues to Search for!

  • Circular tadpole gut…circular poop
  • A tell-tale sign but very cryptic!
  • Flipping rocks can be key

Post-metamorphs

Observational Data:
Post-metamorphs

  • Snout-urostyle length (SUL)
  • Photos | Chin photos
  • Location (X/Y)
  • Time of observation

Incidental Observations

  • Can be valuable source of natural history
  • Tracking distributions over time (CNDDB, iNaturalist)

Night Surveys

  • Suggested by Alvarez et al 2023
  • Viable option in some areas to generate initial “presence”/occupancy detections
  • Less suitable for monitoring populations over time

Other Methods

Audio Surveys

  • Using audio recording units (ARUs) for occupany/detection
    • see Huck et. al (2024) and Lapp et al. 2024
  • BirdNet and SoundHub tools may make this easier

Huck et al. 2024           

Time/Area Constrained Surveys

PIT Tagging

  • PIT tag: a marking tag made of a passive integrated transponder (PIT) that relies on passive radio-frequency identification of a 10-digit hexadecimal number, read with a scanner and portable reader.

e-DNA (Environmental DNA)

Machler et al. 2014. Freshwater Science

  • Filter a lot of water
  • Clean/sterile replicates
  • Cover more ground (but not proof of absence)

e-DNA for Conservation

  • Frameworks already developed (see Adams et al. 2024)

Questions?

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Survey Methods 2025-05-12 Elkhorn Slough RTEP

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  • Survey Methods
  • One thing to remember...
  • Overview
  • There is a balance...
  • What is the objective?
  • Resources
  • Definitions
  • Life Cycle & Survey Timing
  • Timing of Surveys
  • Visual Ecounter Surveys (VES)
  • VES
  • Important to check shoreline
  • and edgewater…
  • VES Snorkeling
  • VES Snorkeling
  • Survey Gear
  • Egg Masses
  • Observational Data: Oviposition
  • Tracking Fate of Eggs
  • Tracking Fate of Eggs
  • from S. Kupferberg,...
  • Larvae
  • Observational Data: Larvae
  • Post-metamorphs
  • Observational Data: Post-metamorphs
  • Incidental Observations
  • Night Surveys
  • Other Methods
  • Audio Surveys
  • Time/Area Constrained Surveys
  • PIT Tagging
  • e-DNA (Environmental DNA)
  • e-DNA for Conservation
  • Questions?
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