Monthly Archives: April 2016
Sawfish are modified rays with a shark-like body. Sawfish get their name from their “saws”, which are used for defense and to locate, stun, and kill prey; mostly fish. The earliest sawfish arose about 200 million years ago. These sawfish were distant cousins of the ones we see today which appeared about 65 million years ago. At one time sawfish were abundant; however, they have experienced significant declines due to decades of unintentional overfishing, mostly the result of entanglements in fishing gear. Sawfish saws (scientifically called rostrums) have also been popular trophy items, but when they’re removed, they don’t grow back and sawfish are unable to feed normally or defend themselves. Today, all sawfish species (five) are endangered, including the smalltooth sawfish which occurs in our area. The smalltooth sawfish historically ranged from around North Carolina to central Brazil, and along the western coast of Africa. Now, smalltooth sawfish are only found in south and southwest Florida, and the Bahamas. With few remaining, it is important to learn about their life history, biology, and ecology so that conservation efforts will be successful.
In Southwest Florida, smalltooth sawfish research began in the early 2000s with most research efforts focused in the Caloosahatchee and Peace rivers; research data and angler observations indicate these areas still support juvenile sawfish. Last month I accompanied FWC-Fish and Wildlife Research Institute (FWRI) researchers on a directed sawfish trip in the Caloosahatchee River. FWRI’s sawfish research includes both random and directed sampling using a variety of net gear. We sampled in areas where anglers and shore observers had reported sawfish sightings (hence directed sampling).Sampling involved deploying a net and letting it soak for one hour. We had to check the net whenever anyone saw movement or after a half hour, whichever came first. Our first set resulted in nothing. We then cruised the shoreline looking for sawfish before setting a second net. We thought we were skunked a second time but finally at the end of our set, we got a sawfish!
It’s cownose ray mating season. It’s also the time of year when I’m frequently asked “what kind of fish is that swimming at the surface with two fins out of the water?” That fish is a female cownose ray and if one looks carefully they will see at least one male, often several, following her at a slightly deeper depth. When a female cownose ray displays her pectoral fin tips above water she is ready to mate.
In Charlotte Harbor, cownose ray mating behavior can occur between October and June but mating usually takes place from April to June. Like all sharks and rays, fertilization is internal. Female cownose rays have two ovaries, but only the left one is functional. Males have modified pelvic fins called claspers that they use to deposit sperm when mating. During mating, the male bites the female to hold onto her. This often leaves visible wounds along the pectoral fins. Sharks and other rays also exhibit this biting behavior. Don’t worry, the wounds heal quickly.
If you’ve spent any time fishing along shore or strolling in our parks along the shoreline of Charlotte Harbor, you’ve probably noticed all the green algae attached to the rocks and other intertidal structure. I walked along the shoreline at Bayshore Live Oak Park and noticed two species of filamentous green algae. One species was closer to the water than the other in what biologists refer to as resource partitioning. I suspect that the one closer to shore is probably better adapted to being periodically exposed at low tide. The other is probably better at competing in deeper water.
Closest to shore I saw Enteromorpha flexuosa. If it has a common name I don’t know what it is. Enteromorpha means “intestine-shape,” and this algae resembles hollow tubes much like intestines. Enteromorpha is light green, unbranched, and only about four to five inches in length, often shorter. It grows in clumps or tufts at or near the low-tide line and is often found on rocks, mangrove roots, or other woody debris. This species of algae has a wide salinity range and can be found in almost any shallow-water brackish or marine environment.