NRES 348 — Lec 14: Fish Early Life Stages & Harvest Theory

What is recruitment in fish populations?

The addition of fish to a population at a defined stage, such as when they become vulnerable to fishing gear or settle on a reef.

What is year-class success?

How successfully fish born in the same year survive & contribute to the population. It can vary greatly between years.

What is the stock-recruitment relationship?

The relationship between the number of spawning adults & the number of new fish recruited into the population.

What is the difference between the Beverton-Holt & Ricker models?

• Beverton-Holt = recruitment increases & levels off.

• Ricker = recruitment increases, peaks, then declines at high spawner abundance.

What is density-dependent compensation in fisheries?

When fewer spawning adults lead to more recruits per spawner, helping the population replenish after harvest.

What is depensation?

When recruits per spawner decrease at very low spawning populations, causing slow or unsuccessful recovery.

Why does the age & size of spawning fish matter?

Stock age & size composition can affect reproductive success & offspring quality, not just the total number of adults.

What are the 3 early life stages of fish?

• Embryonic = nutrition from yolk or mother.

• Larval = rapid development, often weak swimming

• Juvenile = rapid growth & resemblance to adults

What is ontogeny?

The developmental changes in a fish’s body, organs, physiology, & behavior as it grows.

What is the point of no return (PNR)?

The point when a starving fish larva becomes too weak to feed & recover.

What is the match-mismatch hypothesis?

Fish larval survival depends partly on whether the timing of larval production overlaps with the availability of zooplankton prey.

How does starvation & predation affect recruitment?

Poor food supply slows growth & increases exposure to predators. Faster larval growth can improve survival & recruitment.