Description of reared preflexion gray triggerfish, Balistes capriscus. Larvae from the northern Gulf of Mexico Carrie M. Simmons and Stephen T. Szedlmayer SEDAR62-RD-12 June 2019 BULLETIN OF MARINE SCIENCE. 89(2):643–652. 2013 http://dx.doi.org/10.5343/bms.2012.1062 NOTE DESCRIPTION OF REARED PREFLEXION GRAY TRIGGERFISH, BALISTES CAPRISCUS, LARVAE FROM THE NORTHERN GULF OF MEXICO Carrie M Simmons and Stephen T Szedlmayer ABSTRACT Here we describe and illustrate reared gray triggerfish, Balistes capriscus (Gmelin, 1789), larvae from the northern Gulf of Mexico less than 3 mm notochord length (NL). Eggs were collected by scuba divers from active nests with a guarding female. Gray triggerfish eggs had a mean diameter of 0.62 (SD 0.03) mm. Eggs hatched from 24 to 48 hrs after fertilization based on samples brought back to the laboratory. Post-hatch larvae were distributed throughout the water column of the rearing tanks. Larvae were maintained in laboratory rearing tanks but none survived beyond 6 d post-hatch. Morphological development of live gray triggerfish larvae n( = 10) for each day is described and a representative specimen is illustrated. Larvae hatched at a mean size of 2.2 mm NL and 20 myomeres, without pigmented eyes or a functional mouth. This study provides descriptive information on smaller and less developed larvae than has previously been described. This new material will improve researchers’ ability to identify gray triggerfish from field collections. Gray triggerfish, Balistes capriscus (Gmelin, 1789), is a widely distributed species found throughout the Gulf of Mexico and the eastern and western Atlantic Ocean (Briggs 1958, Moore 1967). Homogeneity of mitochondrial DNA sequences be- tween gray triggerfish collected in the Gulf of Mexico and western Atlantic Ocean suggests that there is one stock (Antoni et al. 2011). This widely distributed species can be found in a variety of habitats including artificial reef structures (Frazer and Lindberg 1994, Vose and Nelson 1994, Kurz 1995, Wilson et al. 1995, Simmons and Szedlmayer 2011, 2012) and natural reefs (Johnson and Saloman 1984, Vose and Nelson 1994). Recent stock assessments indicate that the gray triggerfish is overfished in the Gulf of Mexico (SEDAR-9 2006, SEDAR-9 Update 2011). Fishery-independent ichthyoplankton surveys in the Gulf of Mexico, when avail- able, play an important role in the stock assessment process as indices of adult abun- dance (Lyczkowski-Shultz and Hanisko 2007). The National Marine Fisheries Service in cooperation with the gulf states has been conducting ichthyoplankton surveys since 1982 under the Southeast Area Monitoring and Assessment Program (SEAMAP). For these ichthyoplankton surveys to be used as an index of adult abundance, lar- val identification keys are needed. Postflexion gray triggerfish larvae from the Gulf of Mexico and southern Brazil have been described and illustrated (Matsuura and Katsuragawa 1981, 1985, Lyczkowski-Shultz and Ingram 2005). However, the pres- ent study provides new descriptive information of reared preflexion gray triggerfish larvae, which facilitates identification of the earliest stages of gray triggerfish. Bulletin of Marine Science 643 © 2013 Rosenstiel School of Marine & Atmospheric Science of the University of Miami 644 BULLETIN OF MARINE SCIENCE. VOL 89, NO 2. 2013 Methods Eggs were collected from active gray triggerfish nests with a guarding female by scuba divers around artificial habitats that were located 26–50 km south to southeast of Dauphin Island, Alabama, in the northern Gulf of Mexico. Eggs were collected from 2004 to 2006 in June–July during the peak spawning season while reproductive behavior of gray triggerfish was recorded (Simmons and Szedlmayer 2012). Eggs were removed from active nests and placed in 3.8-L plastic bags. At the surface, eggs were placed into aerated coolers at 20 to 21 °C, similar to the bottom water temperature, and transported to the laboratory. Larval rearing was attempted six times from 2004 to 2006 during June and July of each year. Several different methods of rearing gray triggerfish larvae were attempted, but only meth- ods with survival up to 6 d are reported. All larval rearing attempts were completed in a closed system, with gentle aeration. Larvae from three different gray triggerfish egg mass- es were reared in circular polyvinyl chloride (PVC) 200-L containers with the temperature maintained from 21 to 22.5 °C and salinity constant at 33. Stocking density ranged from 10 to 15 larvae L−1. Live wild zooplankton were collected with two 63-μm plankton nets every 2 d. Larvae were fed all zooplankton within the 63–150-µm size fraction daily. Photographs were taken of live eggs and larvae each day. Digital photographs of larvae and a micrometer were taken with an Olympus BH-2 compound microscope with 4× and 10× objective lenses, a Sony AVC-D7 video camera, and a FlashPoint 128-4M digitizing board (Integral Technologies, Inc., Indianapolis, Indiana). Digitized egg and larval images were measured (nearest 0.01 mm) using Image Pro v4.5 software. Measurements of 10 gray triggerfish larvae were taken each day and terminology follows: (1) total length (TL) = tip of snout to end of tail; (2) snout length = tip of snout to anterior margin of the eye; (3) noto- chord length (NL) = tip of the snout to end of the notochord; (4) oil globule in the yolk sac = largest horizontal measure from the anterior to the posterior margin of the oil globule; (5) yolk sac = largest horizontal measure from the anterior to the posterior margin of the yolk sac; (6) eye diameter = largest horizontal measure from the anterior to the posterior margin of the eye; (7) lower jaw length = tip of the lower jaw to posterior margin of the jaw (Matsuura and Katsuragawa 1981, Kimmel 1993, Moser 1996). Illustrations of the larvae were made each day using the digitized images of live larvae. For pigment location, larvae preserved in NOTOXhisto fixative (Scientific Device Laboratory, Glenview, Illinois) were examined using a Leica MZ6 (Leica Microscopy Systems, Ltd., Heerbrugg, Switzerland) dissecting scope and compared with several (3–5) digitized images of live larvae without fixative. Results Mean egg diameter was 0.62 (SD 0.03) mm (n = 90) based on samples from nine different nests (Fig. 1A). Gray triggerfish eggs hatched from 24 to 48 hrs after fertilization based on samples brought back to the laboratory. Rearing at- tempts resulted in larvae living through 6 days post hatch (dph). Post-hatch larvae were distributed throughout the water column of the rearing tanks. The rearing tank height ranged from 0.61 to 1.52 m. Mean morphometric characters of larvae from hatching through 6 dph are shown in Table 1. After rearing experiments were completed and larvae preserved, we examined preserved larval gray trig- gerfish for the presence of a tuft of spinules on the cheek, a characteristic feature of Balistidae larvae. These spinules were detected in preserved larvae, but due to deterioration the exact timing of formation was undetermined. Spinules were not visible in photographs or documented in the illustrations of live larvae. NOTE 645 Figure 1. Photographs: (A) gray triggerfish eggs. Mean egg diameter = 0.62 (SD 0.03) mm; (B) gray triggerfish larvae at 0 d. Larvae hatched without pigmented eyes or functional mouth. Scale bars = 0.5 mm. Day 0.—Mean TL of gray triggerfish larvae at hatching was 2.27 (SD 0.04) mm (Fig. 1B, Table 1). Larvae hatched without pigmented eyes or a functional mouth. At 0 dph, there were 20 myomeres, with four to five pre-anus, 15 to 16 post-anus, and the otoliths were visible. The number of myomeres did not change from 0 dph throughout the study. Nine to 12 melanophores were visible on the anterior por- tion of the oil globule and yolk sac, with four to five melanophores on the dorsal margin of the peritoneal cavity. One to two melanophores were visible on the dorsal portion of the yolk sac. The forebrain, midbrain, and hindbrain were vis- ible, with one melanophore on the forebrain and one to two melanophores on the midbrain. Day 1.—At 1 dph, mean TL was 2.32 (SD 0.02) mm (Fig. 2A). Eyes were partially pigmented, with melanophores spreading from the anterior and dorsal portion of eye towards the ventral margin of the eye. Many overlapping melanophores were visible on the anterior margin of the yolk sac and oil globule. The gut was Table 1. Mean (SD) morphometric measures of live larval gray triggerfish by day n( = 10). Day Total length Snout length Notochord length Eye diameter Oil globule Yolk sac Jaw length 0 2.27 (0.04) 0.10 (0.01) 2.16 (0.04) 0.16 (0.01) 0.18 (0.01) 0.46 (0.02) – 1 2.32 (0.02) 0.11 (0.02) 2.19 (0.05) 0.18 (0.02) 0.18 (0.01) 0.35 (0.02) – 2 2.34 (0.08) 0.12 (0.02) 2.20 (0.06) 0.22 (0.01) 0.15 (0.01) 0.22 (0.02) – 3 2.34 (0.02) 0.13 (0.01) 2.20 (0.03) 0.20 (0.02) 0.11 (0.01) 0.20 (0.02) 0.17 (0.03) 4 2.27 (0.06) 0.10 (0.01) 2.12 (0.05) 0.20 (0.01) 0.08 (0.01) 0.12 (0.03) 0.22 (0.03) 5 2.29 (0.05) 0.11 (0.01) 2.13 (0.04) 0.20 (0.01) – – 0.21 (0.03) 6 2.22 (0.05) 0.06 (0.01) 2.08 (0.05) 0.20 (0.01) – – 0.25 (0.02) 646 BULLETIN OF MARINE SCIENCE. VOL 89, NO 2. 2013 Figure 2. Illustration of gray triggerfish larvae over the first six days post hatch (dph).