The Fishing Concept of “Catching Some, Not All”

When people fish, the goal is rarely to pull everything from the water. Instead, fishermen use methods that selectively catch some fish while letting others escape. This selectivity can be by size, species, or behavior.

Here are the main principles:

1. Selectivity Through Gear

• Hook size: A small hook catches small fish, a big hook catches larger fish, but each excludes the other.
• Net mesh size: Large mesh allows small fish to escape; small mesh traps even tiny fish but may be wasteful.
• Lesson: The tool itself decides what gets caught.

2. Selectivity Through Bait

• Different fish are attracted to different bait. Worms may catch freshwater fish; shrimp bait may attract saltwater species.
• Artificial lures mimic insects or prey that only certain fish go after.
• Lesson: The signal you put out attracts only a subset of fish.

3. Selectivity Through Trap Design

• Pots and cages are designed so only certain animals (crabs, lobsters, bottom fish) can enter.
• Others ignore or physically can’t get in.
• Lesson: Structural design enforces who gets caught.

4. Selectivity Through Depth

• Surface fishing with floating bait catches surface-feeding fish.
• Deep-sea lines target species that live far below.
• Lesson: Where you position your effort (depth) shapes the outcome.

5. Efficiency vs. Precision

• Casting a big net is efficient but messy (lots of unwanted catch).
• Fly fishing is slow but precise (one species at a time).
• Lesson: Methods trade off between scale and accuracy.

Just as different fishing techniques are designed to catch certain types of fish while letting others escape, Snowball Research uses selective stock screening methods to focus on companies that fit specific strategies. For example, it highlights firms that are making strategic or operational changes following a CEO transition. Similarly, screenings of activist 13D filings, fund letters, and 13F disclosures provide additional ways to filter the broader market into a focused set of ideas for further research.