Secondary consumers are organisms that primarily eat primary consumers (herbivores). Based on the list provided, the following organisms would be considered secondary consumers:
- kelp crab (eats primary producers like kelp and can also eat small animals)
- sea otter (eats sea urchins and other marine invertebrates)
- horn shark (eats smaller fish and invertebrates)
- elephant seal (primarily eats fish and squid and can be considered a secondary consumer)
The sea urchin is a primary consumer as it feeds mainly on plant matter, primarily kelp.
Therefore, the secondary consumers from your list are:
- kelp crab
- sea otter
- horn shark
- elephant seal