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Day 3: 7-29-06
Survey Team
- Paula Whitfield
- Christine Addison
- Doug Kesling
Collection Team
- Jay Styron
- Brian Degan
- Wilson Freshwater
- Norbert Wu
Survey dives
Today four dives were completed at an area of low relief live rock approximately 60 miles south of Beaufort Inlet. Although this area did not have the relief of yesterday’s wreck dive on the Naeco, the few available crevices and narrow ledges supported a wide variety of fish and other fauna.
A record number of 16 lionfish were counted on one survey transect, which covers an area 50 m long by 10 m wide. The observed lionfish varied in length, suggesting that they came from different spawning events over an extended period of time.
Collection dives
Live specimens of lionfish were collected today. Collecting live lionfish requires a delicate hand and a careful approach. Divers capture the lionfish with aquarium nets and then carefully transfer the fish to a small mesh bag. Due to expansion of the swim bladder* during ascent, fish need to be vented while the divers are at their 20’ decompression stop. Divers vent the fish by carefully inserting a hypodermic needle into the swim bladder until air bubbles escape, releasing the pressure of the expanded air. This enables the fish to swim upright once again. We have found that venting the fish in this way increases their survival on the surface. Lionfish were also collected using pole spears. Lionfish collections are needed to understand lionfish reproduction (see Day 2) and other life history characteristics such as age, growth, diet, and genetics.
*The swim bladder is a flexible-walled, gas-filled sac located in the dorsal portion of body cavity. This organ aids in buoyancy control. Most of the swim bladder is not permeable to gases. Gas (typically oxygen) is introduced to (increase buoyancy) and removed from (decrease buoyancy) the bladder via a gas gland. One of the risks to a swim bladder is that if a fish ascends too quickly, the bladder can rupture or burst, killing the fish.
Lionfish reproduction studies
Aboard the Nancy Foster, studies on lionfish reproduction continue. We have learned from earlier work that lionfish release multiple batches of eggs per year and are mature at approximately 210 mm total length. Lionfish release their eggs encased in a buoyant gelatinous ball.
Today we collected two lionfish egg balls from a single lionfish using a strip spawning technique. This collection provided new information regarding the number of egg balls each lionfish produces during a spawning event. By counting the eggs in each ball, we obtain estimates of lionfish egg output per spawning event, an important parameter for population modeling.
In addition, we are collecting ichthyoplankton using a bongo net. These collections will be sorted to determine if they contain lionfish larvae. By comparison with past ichthyoplankton surveys, these collections will provide insight into the abundance of lionfish larvae in the ichthyoplankton and could be used to gauge the relative increase in lionfish abundance.
