Egg Production and Completion of the Life Cycle of Belted Sandfish <I

NOTES 701

ElIS/irs/8//a t9X8n8 DensIty va SerlIng Ooefflclent and " Slit + Olay

• 6

Figure 3. Relationship between Eusarsiella texana abundance, sorting coefficient, and percent silt + clay, Marco Island, Florida.

Wilkinson, L. 1990. SYSTAT: the system for statistics. SYSTAT, Evanston, lIIinois. 677 pp.

DATE ACCEPTED: May 12, 1994.

ADDRESS: Collier County Pollution Control Department, 3301 Tamiami Trail East, Naples. Florida 33962.

BULLETIN OF MARINE SCIENCE. 56(2): 701-707. 1995

EGG PRODUCTION AND COMPLETION OF THE LIFE CYCLE OF BELTED SANDFISH (SERRANUS SUBLIGARIUS) IN CAPTIVITY

John W. Tucker, Jr. and Peter N. Woodward

The belted sandfish, Serranus subligarius (family Serranidae) ranges from Tex- as through Florida to North Carolina on hard bottom, from the shoreline to at 702 BULLETIN OF MARINE SCIENCE. VOL. 56, NO.2, 1995 least 80 m depth (Robins and Starck, 1961; Hastings and Bortone, 1980). It is a simultaneous hermaphrodite, maturing at about 1 year, and reaching a maximum size of about 100 mm SL and age of 4-5 years in nature (Hastings and Bortone, 1980). This species and its Caribbean relatives such as the harlequin bass (S. tigrinus) and tobaccofish (S. tabacarius) are sold as aquarium fish. Some members of the genus might be worthy of farming as ornamentals. Spawning behavior of belted sandfish in nature and in aquaria (190 and 380- liter, E. Clark, pers. comm., 1992) was described by Clark (1959, 1965), but egg production was not investigated and no fish were reared. Hastings and Bortone (1980) described habitat, age and growth, feeding, reproductive morphology, and spawning season in west Florida waters. This report focuses on the number and quality of eggs produced by two pairs of captive wild belted sandfish and sub- sequent spawning of two of their progeny.

MATERIALS AND METHODS

The four belted sandfish used in our initial study were caught on 30 September 1990 at 1-2 m depth in the Indian Rive:r estuary just north of St. Lucie Inlet on the east coast of Florida. 1\vo fish were held in each of two 3D-liter(254 mm X 500 mm X 235 mm deep) glass aquaria with undergravel filters, containing short pieces of 25 and 38-mm PVC pipe for cover. In February 1991, pair A fish were about 65 and 70 mm TL, and pair B fish were both about 60 mm TL. During October to February, water temperature was in the range 22-27°C. It was 26.0°C in February when spawning began. From then until spawning ceased in June, temperature was controlled within the range 23-27°C by a 50- watt heater in each tank working against cooling by an air conditioner. Light was not controlled for the fish. Throughout the period (September-June), four 40-watt daylight fluorescent bulbs in the ceiling 85 cm above the tanks provided about 10 f.LE/m2/s at the water surface for 9-14 hlday on weekdays and 0-14 h/day on weekends. A small amount of indirect sunlight entered the room through a north window (80 cm X 12 cm) level with the bases of the tanks and 2.0 m away, resulting in about one- tenth the illumination of the electric lights. Time from sunrise to sunset was 11.5 h when spawning started and 14.0 h when it stopped. During their first 2 weeks in captivity, the fish were weaned from a diet of frozen seafood to an experimental dry pelleted feed containing 60% protein and 10% fat, including 7.7% marine fish oil (feed no. HB9120, described in Tucker, 1992 and Tucker and Wood- ward, in press), HB9120 was the sole diet from mid-October 1991 through June 1992. The fish were fed to satiation. One meal a day was enough until spawning began, but appetites increased so much during the spawning period that two meals a day were required. HB9120 also was the only food given to other sandfish that spawned later. Beginning in November 1993, an improved feed (HB9262) was used. This was not a behavioral study. To determine if spawning would occur, behavior of the fish was observed for 1-6 h each afternoon and night (usually 2-3 h), but not on a regular schedule. On most days, spawning events were witnessed, and several times they were recorded on videotape, The fish also were watched intemlittently during the day. Each morning, all eggs present were removed from the broodfish tanks and counted with a pasteur pipette, Either a sample of 20 or all the eggs from smaller spawns were placed in a beaker with 400 mL of seawater to detelmine combined fertilization and hatching rate (FHR)-i.e., survival from spawning to hatching. Fertilization rate was not determined separately.

RESULTS AND DISCUSSION Early in the season, courtship usually began late in the afternoon (1-3 h before sunset); spawning began near sunset and continued until the room was dark. Late in the season, spawning often occurred during the morning and sometimes in the early afternoon. Clark (1959) reported that this species spawned mainly between ]600 and ]900 standard time in west Florida waters. In the San BIas Islands of Panama, chalk bass (S. tortugarum) are reported to spawn mainly from 160 min before until just after sunset (Fischer and Hardison, 1987). Most serranine simultaneous hermaphrodites in the Caribbean region normally spawn just before sunset (Fischer, 1986). During the spawning period, pair A had more frequent hostile encounters than NOTES 703

Table 1. Spawning data for two pairs of belted sandfish in 30-liter aquaria

Combined fertilization & hatching ratc

Temperature Length or No Number of eggs per day 100% spawning spawn FHR Min. Mean Max. period days Min.* Mean* Max. Zeros Min.* Mcan* (% or Pair ("C) (0C) (0C) (d) (No.) (No.) (No.) (No.) (No.) (%) (%) all)

A 23.3 25.8 27.2 91 45 2 88 657 5 5 69 8 B 23.4 25.6 27.3 81 2 12 823 1,732 1 45 92 43

* Zero values were excluded from calculations. pair B, with the larger fish usually dominating. Pair B fought occasionally during the day, but those fish were more compatible and easily settled into the spawning routine each afternoon. The belted sandfish usually is solitary and defends feeding territories but forms pairs for spawning in the late afternoon and probably is serially monogamous (Fischer, 1986). Confinement in an aquarium increases ag- gression when the fish are not spawning. The belted sandfish is capable of self- fertilization (Clark 1959; Hastings and Bortone, 1980); however, nearly every day we observed our fish pair-spawning or preparing to do so, and there was no behavioral evidence of intentional self-fertilization. Pair B produced 16 times more eggs than pair A, with a 33% higher average FHR (Table 1, Fig. 1). Pair A spawned 46 times in 91 days (11 Mar-9 Jun), producing 4,042 eggs (88 eggs/day) and 2,789 hatchlings. For this pair, the first spawn was average (78 eggs) and the last large (234 eggs). Average combined fertilization and hatching rate (FHR) was 69%. Pair B spawned 79 times in 81 days (26 Feb-17 May), producing 65,054 eggs (823 eggs/day) and 59,589 hatchlings. The first spawn was small (454 eggs) and the last very small (68 eggs). Average FHR was 92%. The only two days that pair B did not spawn were 11 and 12 Mar when water temperature dropped from 26.0°C to 23.4°C during a cold front. Pair Ns first two spawns were on 11 and ]2 Mar, but consisted of only 78 and 25 eggs. The spherical, buoyant eggs had a mean diameter of 662 f.Lmand a single oil globule. To investigate possible effects of the lunar cycle on egg production, the fol- lowing procedure was followed. Data sets for both pairs were detrended by linear regression (egg number vs. lunar day). This removed any progressive increase or decrease in the data over the evaluation period. Detrending produces a data set that has a mean of zero and a standard deviation of one. The data sets were further smoothed by conversion to 5-day (pair A) and 7-day (pair B) moving averages. Such filtering reduces random noise associated with most data sets and allows detection of possible periodic frequencies. Autocorrelation analysis for pair A revealed three significant frequencies. There were two positive correlations: the first at I-day lag (r = 0.864, N = 93) and the second at 6-day lag (r = 0.247). Also, there was a negative correlation at 8-day lag (r = -0.284). The autocor- relations basically mean that egg number observed today is strongly associated with the number observed yesterday. The 6-day lag means that egg number today is significantly associated with that observed 6 days ago. The negative autocorrelation indicates that if a large number of eggs is produced today, 8 days from now few eggs should be produced. Pair B had a single significant positive autocorrelation at I-day lag (r = 0.653, N = 81). No relationship between egg number and the lunar cycle was evident in this analysis. Size of spawns by pair B did not seem to be affected by temperature in the range 24-27°C (Fig. 2). To determine possible relation between egg number and temperature, a linear regression was performed. The regression was not significant 704 BULLETIN OF MARINE SCIENCE, VOL. 56, NO.2, 1995

Pair A 500

0 A 0 7 14 21 28 35 42 49 56 63 70 77 84 91 98 105

0 0 0 0 ~ • • • • 0 2000 a: 1&.1 11. Pair B (f) 0 0 1&.1 1500 "-0 a: 1&.1 m 2 ::> z 1000

500

o 7 14 21 28 35 42 49 56 63 70 77 84 91 98 105 FEB MAR APR MAY JUN

Figure 1. Egg production by two pairs of belted sand fish in 30-1iter aquaria, Full (clear) and new (dark) moons are indicated,

(,-2 = 0.007, N = 79, P = 0.965). To determine if egg numbers were randomly distributed in relation to temperature, the regression residuals were plotted in a normal probability plot. They fell in a straight line, indicating that they were from a normal (random) distribution. Therefore, there is no reason to believe that temperature affects the number of eggs produced, within the limits of this study. Temperature outside the spawning range will, of course, limit spawning. Pair B produced more eggs and pair A fewer eggs than S. tortugarum of similar size (Fischer, 1986; Fischer and Hardison, 1987). Six chalk bass (2-4 per 80-liter aquarium, at 27°C) produced an average of 250 eggs per fish per day (Fischer and Hardison, 1987). Two adult belted sandfish were raised from eggs spawned by pair B on 23 Mar 1991. At 24.6-26.4"C (mean 25.6°C), they hatched in slightly less than a day, and developed complete eye pigmentation and first fed within 2.5 days after hatch- NOTES 705

2000

Pair B ·. ?( 1500 c 0:: • W a.. •• (I) I. • • C) • • C) 1000 .:. • . • W · I.&.. •. • • 0 • ·• • •• •••· • 0:: • • w • m .· • :::5! 500 ::> ·· • z •

• • • • 0 •

23 24 25 26 27 28 TEMPERATURE (DC)

Figure 2. Number of eggs spawned per day by belted sandfish pair B vs. water temperature. ing (dah). They were fed rotifers (Brachionus plicatilis) and 0-2 day old Artemia. The rotifers and Artemia had been fed Nannochloropsis oculata and Tahitian Isochrysis. Rotifers and 1-2 day old Artemia were enriched for 2-5 h with Frippak Booster microcapsules. At 23.0-28.1oC (mean 25.6°C), transformation was complete and the juveniles had settled by about 34 dah. The fish ate pellets when first offered to them at 46 dah, and no further live food was provided. Most specimens from this rearing trial were preserved. On 26 Mar 1992, each of the two remaining reared fish was paired with a wild fish in a 30-liter tank in a different room (61- mm wild with 62-mm reared; 70-mm wild with 71-mm reared). On 9 Oct 1992 (age 16.5 months), the first pair spawned 32 eggs with an FHR of 95%. During the 18 d before spawning, water temperature was 25.1-26.8°C, and on the day of spawning it was 25.9°C. Thus the life cycle was completed in captivity, but the pair did not spawn again for at least 11 months, probably because of variable conditions or disturbances in the new room. During 1992-1993, the original two pairs, the two mixed pairs, and two new wild pairs of belted sandfish were kept in 30-liter tanks in the second room. All except the second mixed pair spawned sporadically over a temperature range of 2I.9-28SC during June, July, September, October, November, and December, but spawns at less than 24.0°C always were small «80 eggs). At the end of April 1994, two pairs completely isolated from each other (one under controlled conditions and the other ambient) began spawning less than a 706 BULLETIN OF MARINE SCIENCE, VOL. 56, NO.2, 1995

day apart. On 31 December 1993, the 30-liter aquaria had been moved into a third room with better environmental control. Fluorescent lighting was on during 0600-2200, During 27 April to 30 May 1994, the second reared sandfish (age 37 months) spawned with its wild mate (both -80 mm TL) every afternoon. Spawn- ing occurred mostly during 1500-1700 standard time. Daily egg production usually was in the rangt~500-2,000, Fertilization was typically 96-100%, and hatching rate when checked once was 92%. Water temperature had dropped to 22.3°C on 3 February and 23,0°C on 5 March, The range during the 30 days before spawning was 24.9-27.2°C. During April to October 1994, all four pairs in aquaria spawned frequently: original wild pair B, 47 times in 127 days, 9 June-13 Oc- tober; first reared -+- wild, 28 times in 88 days, 14 June-9 September; second reared + wild, 104 times in 181 days, 27 April-24 October; new wild pair, 22 times in 121 days, 9 June-7 October (temperature range 25,0-28.4°C). During 28 April to 24 July 1994 (88 days), a pair of wild sandfish (both -90 mm TL) spawned 55 times. in a 750-liter (231 cm X 72 cm X 45 cm deep) concrete tank in a shaded greenhouse with 10% transmitted natural light. They had been in the tank under essentially ambient conditions for more than a year. Most eggs were produced during 1100-1300 (sunrise at 0543-0533; sunset at 1849-1901). Usually, 2,00Q.-3,000 eggs were found each day. Fertilization rate once was 97% and hatching rate usually 90-100%. Temperature for the previous 30 days was 25.0-27SC, and during spawning, 26.0-27SC. Belted sandfish normally spawn during April-September in Florida waters (Has- tings and Bortone, 1980). Through environmental conditioning, we have obtained both accelerated (winter-spring) and delayed (fall) spawning. Performance of pair B might be representative of spawning in nature under optimal conditions (i.e., compatibility, low stress, good nutrition, relatively constant environment). Over a 3-year period, seven pairs of belted sandfish held in four different environments spawned over a wide daylength range (11.5-16 h), but narrow temperature range (usually 24-27SC). Obtaining eggs for research or commercial culture of the belted sandfish and some of the other Serranus spp. should be relatively easy.

ACKNOWLEDGMENTS

The belted sandfish work was part of a study on culture of serranids partly funded by the U.S. Department of the Interior in cooperation with the U.S. National Sea Grant Office, We thank G. A. Curtis (Indian River Mosquito Control District) for doing the statistical analyses, This is Contribution No. 1043 from Harbor Branch Oceanographic Institution.

LITERATURE CITED

Clark, E. 1959. Functional hermaphroditism and self-fertilization in a serranid fish. Science 129: 215-216. ---. 1965, Mating of groupers. ~'latural History 74: 22-25, Fischer, E. A. 1986. Mating systems of simultaneously hermaphroditic serranid fishes. Pages 77fr-784 in T. Uyeno, R. Arai, T. Taniuchi :md K. Matsuura, eds, Indo-Pacific fish biology: proceedings of the Second International Conference on Indo-Pacific Fishes. Ichthyological Society of Japan, Tokyo. --- and P. D. Hardison. 1987. Ibe timing of spawning and egg production as constraints on male mating success in a simultaneously hermaphroditic fish, Environmental biology of fishes 20: 301-310. Hastings, P. A. and S. A. Bortone. 1980, Observations on the life history of the belted sandfish, Serranus subligarius (Serranidal~).Environmental biology of fishes 5: 365-374. Robins, C. R. and W. A. Starck, n. 1961. Materials for a revision of Serranus and related fish genera. Proceedings of the Academy of Natural Sciences of Philadelphia 113: 259-314. Tucker, J. w., Jr. 1992, Marine fish nutrition. Pages 25-40 in G. Allan and W. DalI, eds. Proceedings of the Aquaculture Nutrition Workshop, Salamander Bay, 15-17 April 1991, New South Wales Fisheries, Brackish Water Fish Culture Research Station, Salamander Bay, Australia, --- and P. N. Woodward. In press. Nassau grouper aquaculture. In Proceedings of the International Workshop on Tropical Groupers and Snappers, 2fr-29 October 1993, Campeche, Mexico, EPO-MEX and ICLARM. NOTES 707

DATE ACCEP1ED:June I, 1994.

ADDRESS: Harbor Branch Oceanographic Institution, 5600 North U.S. Highway J, Fort Pierce, Florida 34946.

BULLETIN OF MARINE SCIENCE, 56(2): 707-710, 1995

MERCURIAL POLLUTION IN THE SEAGRASS THALASSIA TESTUDINUM (BANKS EX KONING)

Daisy Perez

Mercurial pollution in Venezuela's coastal area has been demonstrated for several years, especially at the Golfo Triste region, Parra (1974) suggested that sed- iments in Cafio Alpargaton were polluted by mercury, at levels exceeding 3 ppm. This water course served as a collector of waste lagoons from a Petrochemical Complex operating since 1956 up to 1976, producing NaOH and HCl through an electrolytic process using metallic mercury electrodes. Previous reports on this subject indicated significant levels of mercury found in some marine organisms, like sea stars (Iglesias and Penchaszadeh, 1983) and several fish species (Monaco and Ozaeta, 1979; Urich, 1981; Ishizaki and Urich, 1985). Given the great importance that seagrass communities have in coastal ecosys- tems, it is necessary to know the present degree of mercurial pollution in seagrasses bordering the mercury disposal area. A key objective of this work was to assess the mercurial concentration in water, sediment samples and in Thalassia testudinum, collected from the polluted zones. These results have been compared to the concentrations in samples taken from a mercury-free coastal zone, consid- ered as baseline data.

METIfODS

Thalassia testudinum was sampled at times and locations detailed below, selecting whole and un- damaged plants, with similar size and general appearance. At the same time, sediment and water samples were collected. Collecting Stations.-Punta Mor6n: IQo30'00"N, 68°06'48'W, located in the central zone of the Golfo Triste, is characterized by a regular, low and sandy beach. Thalassia testudinum seagrass beds are between 20 em and 1.5 m deep. Cayo Animas: IQo49'00"N, 68°15'48'W, located in the Morrocoy National Park, is a complex system of water bodies interconnected by channels, surrounding islets or small islands made up of mangrove swamps. Coral reefs and beds of seagrasses of T. testudinum are frequent. Cayo Animas seagrass is also present at depths from 50 em to 2 m. Los Totumos Bay: IQo33'20"N, 66°02'56"W, located east of Codera Cape, between Punta Crucecita and Punta Castillito is a 300 m coastal bay, surrounded by mangrove swamps. Coral reefs and seagrass beds of T. testudinum and Syringodium filiforme are frequent. Seagrass beds of Thalassia here are in depths from 20 em to 1.5 m. Plants, water and sediment collections were made quarterly during the year. Immediately after collection, plants and surficial sediment samples were frozen. Water samples were treated with con- centrated nitric acid before freezing. Mercury Determination.-Water samples (100 ml) were taken in duplicate and the mercurial concentration was determined in a Perkin Elmer Atomic Absorption Spectrophotometer (Mod. 2380), by the cold vapor method (Beaty, 1978). Sediment Samples. A I-g aliquot from each sediment sample was taken in duplicate. Each aliquot was