Strand Crab
Source: Pet Battle. The low tide reveals the colonies of strand crabs and the sound of their clicking dance as they feed upon small creatures hidden in the sand. Aquatic type. I've not seen them actually spawn in Ashenvale, but they sometimes appear as secondary pets there.
The Strand Crab is a wild pet found across multiple continents, appearing both as a primary spawn and as a secondary pet alongside other wild battles.
Guide awaiting review
Hunt Strand Crabs Wild
Strand Crabs appear as secondary pets in Ashenvale and Dragonblight, where they show up alongside primary pets such as the Tundra Penguin. Engage wild battles in those zones to encounter one as a secondary combatant.
Use a Crab to Capture
Bring a crab pet of your own into the capture battle and use Renewing Mists combined with Shell Shield — Renewing Mists keeps your crab healed through prolonged battles while Shell Shield reduces incoming damage enough to nearly negate multi-turn abilities, giving you plenty of time to land a trap.
Understand Surge Priority
The Strand Crab's Surge ability states it always goes first, but if an opposing pet uses a similar speed-boosting ability and ends up with a higher speed value that round, that opponent will act first — Surge works by boosting speed on the round it is used, not by guaranteeing absolute priority.