Aquatic Species Monitoring Flashcards

A biologist applies a power analysis before designing a fish monitoring study. What is the primary purpose of this analysis?

Answer: Determine the minimum sample size needed to detect a specified effect with acceptable Type I and Type II error rates

Power analysis balances the risk of false positives (Type I error) and false negatives (Type II error) to determine adequate sample sizes for reliable inference.

In the context of freshwater mussel monitoring, what does the term 'recruitment' specifically refer to?

Answer: The addition of newly settled juvenile mussels (glochidia transformed to juveniles) to the monitored population

Freshwater mussel recruitment describes the successful transformation of parasitic glochidia on host fish into free-living juveniles that settle into the substrate.

Which habitat variable is most commonly used as a surrogate for salmonid redd density when direct redd counting is not feasible?

Answer: Percentage of suitable spawning gravel substrate within a reach

Spawning gravel availability limits redd-building sites, and the proportion of suitable substrate closely predicts potential redd density in many systems.

A fisheries biologist observes that electrofishing CPUE for walleye has doubled over five years at a reservoir site, but angler catch rates have remained flat. Which explanation is most plausible?

Answer: Increased fish density in shallower habitats sampled by electrofishing due to habitat change, without an overall population increase

Habitat shifts can redistribute fish into areas sampled by electrofishing without changing total abundance, creating apparent CPUE trends that do not reflect population growth.

When using acoustic telemetry to study fish movement in a large river, what is the term for the probability that a tagged fish in range of a receiver is actually detected?

Answer: Detection efficiency

Detection efficiency quantifies the fraction of transmitter pings from a fish within receiver range that are successfully logged, and it varies with tag output, current, and noise.

A state fisheries agency samples a lake using trammel nets over three nights and calculates CPUE for northern pike. Which source of variation is trammel net CPUE most susceptible to?

Answer: Nightly water temperature and moon phase affecting fish activity and net avoidance

Passive gear CPUE for predatory fish like northern pike is highly sensitive to behavioral changes driven by temperature and light conditions, which alter movement and net encounters.

In endangered species monitoring, which statistical model is used to estimate occupancy probability while accounting for imperfect detection across multiple survey visits?

Answer: MacKenzie et al. single-season occupancy model

The MacKenzie et al. occupancy model uses repeated surveys at sites to separate true absence from undetected presence, yielding unbiased occupancy estimates.