All Fishes look different but they do share four characteristics in common.
These characteristics enable fishes to live more successfully in their aquatic environments. Because fishes are water-dwelling animals, they need to have oxygen gas for metabolism from the water around them. To get dissolved oxygen gas from the water, they force the water from the mouth, and send it over the gills and out through the gills silts. The vertebral column surrounds and protects the dorsal nerve cord. It is composed of many hollow bones called vertebral that are stacked on top of one another.