Townsend Cromwell
TC-99-04 Lobster Tagging
TC-99-04 Lobster TaggingMarch 24-April 21, 1999
April
5, 1999 Happy belated Easter to everyone
from Necker Island. To date, we have tagged (below left) and released 660
spiny lobsters. The National Marine Fishery Service (NMFS)
Scientists will hopefully learn much on the movement and survivability of
spiny lobsters from the return of a portion of these tags and related data.
The study is dependent on area fisherman from which we hope to receive any
tags they recapture. Some recaptures will also come from this ship when
we return to Necker in June to conduct a lobster assessment survey on the
slipper and spiny lobster populations. The results of that survey are used
to calculate the size of the lobster population and determine the amount
of fishing the lobsters can safely support. Two days ago, we had a storm pass north of our location which resulted in some impressive 12 foot swells rolling through our test area. Thankfully we were spared from the 40 knot (44 mph) winds the gale contained. Following yesterday's lobster trap set, we moved to the 100 fathom (600 feet) bottom contour surrounding the reef and bottom fished in search of juvenile Onaga (a red snapper much prized for its taste). The Onaga juveniles are for another study being conducted by NMFS Scientists. After the bottom fishing operations, we moved to shallower water and set anchor for the night. It wasn't long before our deck lights began to attract a menagerie of creatures for us to watch. The first animals attracted were swarms of tiny animals ranging from the size of a toothpick to the size of this dot (.). These animals are a portion of the vast collection of animals collectively termed "zooplankton" (animal plankton). Many of these tiny animals use moonlight to guide their daily migration from the ocean's depths to the night surface waters where they feed on the abundant "phytoplankton" (plant plankton) located there. On the surface, the zooplankton confuse the ship's lights for moonlight and are drawn to it.
Next to arrive were small fish and squid which feed on the tiny wiggling, zipping, darting shapes of zooplankton. Many of these fish had large luminescent eyes which reflect bright red under light. From the ship's decks, these reflections can look like tiny moving red "lights". Some of the larger fish (6-9 inches long) possessed huge pectoral (side) fins which they kept loosely folded alongside their bodies as they swam through the plankton feast. As time wore on, a couple of 5 foot gray reef sharks and a number of 20-60 lb. uluas (Jacks) appeared below the smaller surface fish. The gray reef shark and the ulua are among the top reef predators in Hawaiian reefs. At regular intervals, the uluas made lightening dashes to the surface in pursuit of the smaller fish while the sharks made less frequent and less energetic rushes at fish deeper down. Two hours into the anchorage, we were treated to a rare treat as a pod of bottled nosed dolphins began patrolling the outer boundary where the ship's lights ended. We could see the 8 foot long mammals gliding below the surface,
their heads moving from side to side as they scanned the area with their sonar. Soon after their arrival, the lead dolphin directed his head straight at a 9" fish about 20 feet away. I know from experience that the dolphin's sonar had picked up a potential prey, and his sonar had switched from search mode (a regular series of clicks similar to a ticking clock), to a barrage of clicks like a machine gun enabling the dolphin to receive more detailed information on the item of interest. An instant later, the dolphin's image became a blur as it accelerated like a race horse out of the gate. The fish reacted instantaneously (possibly made aware by the barrage of sonar), as it leapt (literally) into motion, shooting like an arrow out of the water and snapping open those huge pectoral fins into the "wings" that flying fish are famous for. Once airborne, the fish banked to its left, gliding with the wind to carry it further. In the process, it lost altitude and as it neared the surface, it dipped the stiffened, lower part of its tail into the water and scuttled furiously. The action enabled it to regain air speed and it climbed higher to sail out of sight about 7 feet above the water. The dolphin however, detected the scuttling and altered course to follow the fish into the night. This scene was repeated over and over
again until the dolphins departed in the early morning.
- For related information about lobster research, visit the Honolulu Laboratory's Kewalo Research Facility Lobster Research web pages.