BEHAVIOR PATTERNS and SEXUAL DIMORPHISM in the SPOTTED DRAGONET, DIPLOGRAMMUS Pauclradiatus (PISCES: CALLIONYMIDAE)

BULLETIN OF MARINE SCIENCE, 60(3): 872-893, 1997

BEHAVIOR PATTERNS AND SEXUAL DIMORPHISM IN THE SPOTTED DRAGONET, DIPLOGRAMMUS PAUClRADIATUS (PISCES: CALLIONYMIDAE)

Michael E. Harrington

ABSTRACT Dragonets (Pisces: Callionymidae) have long been recognized as exhibiting high degrees of sexual dimorphism. In the century following Darwin's (1896) suggestion that sexual dimorphism in Callionymus lyra has evolved through sexual selection, there has been no pub-

lished research on sexual selection in any species of dragonet. The present study provides II detailed description of sexual dimorphism in the spotted dragonet, Diplogrammus pauciradiarus, as well as a description of the behavior patterns involved in courtship, spawning, and agonistic interactions. Observations in the field and laboratory revealed the conIext in which sexually dimorphic traits were expressed, thus providing a basis for future research on sexual selection. Like most dragonets, the males of D. pauciradiarus are larger than the females, and the former develop longer dorsal and caudal fins. Males can also develop black pigmentation on the lower jaw (mouth bar), a black bar across the eye (eye bar) and orange pigmentation on the head. and all three pigment patterns are accentuated (if present) during courtship and agonistic encounters. Males are highly aggressive toward each other and form dominance hierarchies. During both courtship and agonistic encounters, males perfornl lateral displays that involve raising the first dorsal fin. Spawning occurs during the last 2 hours of light (dusk) and involves ascending into the water column to release pelagic eggs. Because the sexually dimorphic traits of the males are involved in both courtship and agonistic behavior patterns. they may have evolved in response to either female mate choice, male-male competition, or a combination of both selective forces. Comparisons are made with other dragonets, though the behavior of most species remains unstudied.

For at least 100 years, dragonets (Pisces: Callionymidae) have been noted for exhibiting high degrees of sexual dimorphism (Darwin, 1896), and it is often suggested that the differences between males and females of a species have evolved due to sexual selection. For example, Holt (1898) hypothesized that the sexually dimorphic characters in males of Callionymus lyra evolved through sexual selection via female choice. But in the century that followed, studies of sexual selection have been published for species in all the other groups mentioned by Darwin (except the Callionymidae), including cichlids, cottids, goldfish, pipefish, salmon, sharks, sticklebacks, swordtails, and wrasses. To study the possible selective pressures responsible for the evolution of sexual dimorphism in a species, one must first document the dimorphic characters and the behavior patterns in which the characters are expressed. Sexual dimorphism in the spotted dragonet, Diplogrammus pauciradiatus. and other species within the family Callionymidae, has been documented to some degree (Chang, 1951; Davis, 1966; Takita et al., 1983), but a more detailed description is needed to choose traits that likely influence the reproductive success of both males and females. In addition, little is known about the behavior of any dragonet species. Thus, it is essential to document behavior patterns (particularly those involved in aggression, courtship, and spawning) before attempting to study how sexually dimorphic traits and behavior patterns influence reproductive success in these animals. Thus, the formation of an ethogram for D. pauciradiatus is a necessary prerequisite to experiments on sexual selection.

872 HARRINGTON: D. PAUC1RAD1ATUS BEHAVIOR PATTERNS AND DIMORPHISM 873

The behavior patterns described in the ethogram are organized according to the scheme used by Myrberg (1972) with the following exception: color patterns are described in a separate section on sexual dimorphism. More recently published ethograms have additional designations of social vs. non-social behavior patterns (Clayton and Vaughan, 1988; Almada et al., 1990; Santos and Barreiros, 1993). This is a potentially misleading categorization, particularly for motor patterns that are used in both courtship and agonistic encounters (social by definition). Because males of D. pauciradiatus are not territorial and do not build nests, patterns such as staring are not included, though they may take on additional meaning when performed from a nest (Santos and Barreiros, 1993). Although quantitative analyses, such as sequential contiguity analysis (Myr- berg, 1972), were not carried out to confirm the groupings of motor patterns, many behaviors of importance to research on sexual selection (e.g., courtship) are highly ritualized and their occurrences are predictable. Aggressive encounters are more variable, but dominance relationships can be determined using simple behaviors like chase, flee, and lateral display. Thus, the following ethogram will provide a sufficient basis for subsequent experiments on female mate choice and male-male competition in D. pauciradiatus (Harrington, 1996).

MATERIALS AND METHODS

Sexual Dimmphism.-Individuals were collected from sites in Biscayne Bay, Florida (Fig. I), during most months in 1993 and all months in 1994 (I.5-m-wide pushnet with 3-mm mesh). All fish were measured using either a ruler or dial calipers. Color patterns were observed in both the field and laboratory, and many individuals were observed in the laboratory while they were anesthetized with tricaine methane sulfonate (MS-222). The addition of MS-222 also enhanced the coloration of males with respect to mouth bar and orange head pigmentation (see Results), as both pigment types can fade when the fish are handled (i.e., stressed). A Wild dissecting microscope was used to observed the genital openings and other small structures (e.g., preopercular spines). Separate pushnet samples were obtained at site A (Fig. 1) during November, 1994, and September, 1995, and all dragonets collected were preserved in 70% Ethanol. The following data were obtained using dial calipers (nearest 0.1 mm): standard length as defined by Davis (1966), left pelvic fin-length (length of longest ray), first dorsal fin-length (length of longest spine), and caudal fin-length (length of longest ray). Pigmentation patterns were also recorded. Fin-length comparisons were made between males and females and between males with and without mouth bars and orange pigmentation. In each case, fin length was plotted against standard length, and a regression line was generated using Cricket Graph 1.2 on a Macintosh IIsi computer. Each pair of regression lines was first tested for differences in slope (0. = 0.05) using a two-tailed t test. If the slopes were not significantly different, the elevations were compared (0. = 0.05) in a second t test (Zar, 1984).

Behavior Pattems.-Field observations were made using snorkel and SCUBA at site A (Fig. I), the time of day varying from early afternoon to dusk. Laboratory observations (over 200 h) were carried out on single- and mixed-sex colonies. The number of individuals in mixed-sex colonies ranged from 30 (15 males and 15 females) to 8 (2 males and 6 females). Fishes were housed in 400-800 liter aquaria (92-184 X 47 X 62 cm) with sandy substrate (3 cm deep) and plastic seagrass. Salinities were maintained at 34%0, temperatures ranged from 24° C to 27° C, and the tanks received fluorescent white light from 07:00 to 19:00. Colonies were observed during all hours of light. All colonies were fed frozen brine shrimp chopped into small pieces (single-edged razor blade) to facilitate feeding, es- pecially among the smaller females. Laboratory observations were supplemented with video tape recordings and 35-mm photography. These records allowed for more detailed analyses of behavior patterns in which rapid movements occurred (i.e.. lateral displays). Laboratory observations of spawning were confirmed by the collection of fertilized eggs in the aquaria. This was accomplished by passing a 30-cm2 net (500-f..Lmmesh) through the upper 30 cm of the water column 8-12 times. The contents were then transferred to a 1000-ml container of water from the same aquarium. Eggs were observed immediately, and larvae were observed on the following day. 874 BULLETIN OF MARINE SCIENCE. VOL. 60. NO.3. 1997

3 KILOMETERS

_ /"lVIRGINIA 1 ~ KBY N 4KBY BISCAYNE ~ ;

SAFETY VALVE ..

" f .. I n J 0 m BAY rf V '<:] 11 t} CD BLLIOT!' KEY !j . J f ~:~

Figure I. Collection sites for D. pauciradiatus in Biscayne Bay, Florida. Marked areas were sampled with a 1.5-m-wide pushnet (3-mm mesh). The highest densities of fish were collected at sites A and B.

RESULTS Sexual Dimorphism.-More than 900 dragonets were collected over the course of the study, and the length-frequency distributions for males and females are shown in Figure 2. The maximum standard lengths were 43.0 mm (males) and 29.0 mm (females). The maximum lengths of the first dorsal fin were 74.1% (males) and 33.3% (females) of the standard length. The maximum lengths of the caudal fins were 56.0% (males) and 33.5% (females) of the standard length. Males (~ 9 mm SL) possess external genital papillae that are recognizable under a dissecting microscope. No such structure is present in females at any size. These results are summarized in Table 1. The overall mottled, sandy color of this species is not sexually dimorphic, but individuals altered their overall "darkness" on differently colored substrates HARRINGTON: D. PAUCIRADIATUS BEHAVIOR PATTERNS AND DIMORPHISM 875

60 I:J Males (n=596) • Females (n=316) 50

I-< QJ 1 40 Q

'.5 30 o Eo-<

9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 Standardlength(mnl)

Figure 2. Length-frequency distributions for all males and females of D. pauciradiatus collected during the present study for laboratory observations or experimentation. Fishes were collected using a push net at the sites marked in Figure 1. All size classes from early juvenile (9-12 mm SL) to large adult (females: 24-29 mm SL; males: 37-43 mm SL) are represented.

(Douglas and Lanzing, 1981). The mottled pattern does, however, extend over the posterior ventral surface of larger males (Fig. 3). A small number of males «5 %) were observed to have an overall greenish color, and a small number of females « 10 %) had an overall orange color, lighter and more brown than male orange pigments (see below). Many males (-75%), henceforth termed barred, possessed black pigment along the dorsal surface of the lower jaw, forming a bar across the mouth (Fig. 3). Males also possessed black pigments in the shape of a diagonal bar across the eye (Figs. 3, 4). This bar was exposed or hidden rapidly and moved with eye rotation. Some males (-25%), henceforth termed colored, possessed orange pigmentation (sometimes with a red component) around the anterior-most portion of the head and the tissue around the eye, and it could extend ventrally along the throat region, to the insertion of the pelvic fin. Large males «25 mm SL) also possessed an iridescent blue pigment on the head in the cheek area and, sometimes, at the base of the pelvic fins. This coloration was much more subtle than the mouth bar or orange face pigmentation., and was intensified during courtship and aggression. The above pigments may always be present, but all were intensified during courtship and agonistic encounters. No females were found to possess any of the above pigment patterns. In males, the pelvic, anal, and caudal fins all became darkly pigmented during agonistic encounters. The pigment appeared and disappeared rapidly (1-5 sec). The pelvic fins were the first to change and had much higher densities of pigments than did the other fins (Fig. 4). The degree of pigmentation varied within an individual and appeared to reflect the level of aggression of the male. The first dorsal fin of males had 2-3 black spots on the tissue between DI and DI1, as well as 1-3 black spots on the tissue between DII and DIV (Fig. 4). In large males «25 mm SL), the tissue covering the elongated filaments of DI-DIV was lightly 876 BULLETIN OF MARINE SCIENCE. VOL. 60. NO.3. 1997

c 0) '"0) c..•..

.... c:: 0) J:)'" '"

o oi N HARRINGTON: D. PAUC1RADJATUS BEHAVIOR PATTERNS AND DIMORPHISM 877

Figure 3. Courtship and spawning behaviors in D. pauciradiatus. A: courtship lateral display by a male (right), resulting in flight by the female (note the tilting of the male's dorsal fin toward the female and the sand displaced by the male's caudal fin motion); B: courtship lateral display by a male (left) in parallel orientation to the female (note the males mouth bar, eye bar and straight body posture); C: the start of a spawning ascent after the pair has performed locking while parallel swimming; 0: apex of a spawning ascent into the water column, the female's body (right) curving inward as eggs are released (note the ventral pigmentation of the male). Scale (D): male-31 mm SL; female--19 mm SL. pigmented. In females and small males «15 mm SL), the first dorsal fin was dark brown to orange with a white area between the first two spines (Fig. 4). There was also a matching brown color between the last two rays of the second dorsal fin. All large males possessed a similar pigment pattern on the tissue covering the preopercle (cheek). There were three darkly pigmented patches which formed a triangular pattern. Females differed from the males in that the two most posterior patches of pigment blended together to form a bar pattern (Fig. 4). Although the bar tended to fade after preservation, it was a reliable character in rapidly iden- tifying the sex of live individuals without having to look at the dorsal fin or genital opening. This was particularly the case with newly captured individuals. A sununary of the above findings is shown in Table I. Fin Lengths vs. Sex and Pigmentation.-A total of 147 males and 169 females were collected for these analyses, and the length-frequency distributions for males and females are shown in Figure 5. All fishes were included when comparing males and females. The smallest male with a mouth bar or orange pigmentation was 17.5 mm (SL), so only those males longer than 17 mm (SL) were included 878 BULLETIN OF MARINE SCIENCE. VOL. 60. NO.3. 1997

Figure 4. Sexually dimorphic traits and agonistic behavior patterns in D. pallciradiatlls. A: adult male (40 mm SL) performing an agonistic lateral display (note the curved body posture, elongated first dorsal fin-spines, and pigmented pelvic and caudal fins); B: adult female (19 mm SL) performing a first dorsal fin wave in which the fin is moved side-to-side (note the pigment on the first dorsal fin, pigment between the last two rays of the second dorsal fin, and the two pigment patches on the cheek that blend together to form a bar pattern); C-D: two males performing agonistic lateral displays while circling (note the anti-parallel orientation, darkly pigmented pelvic fins, open mouth with mouth bar, eye bar, and the bite mark on the third dorsal fin spine of the male in C). when comparing barred and/or colored males to unbarred and uncolored males. As expected, males developed longer first dorsal fins than females, and the size difference appeared at a standard length of only 14 mm (Fig. 6). There was no difference between barred and/or colored males and those males without the pigments. The slopes of the regression lines were significantly different (Fig. 6), but the lines moved toward convergence at approximately 29 mm (SL), and there was no clear separation of the two groups in this size range. Males developed longer caudal fins than females (Fig. 7), but the size difference did not appear until a standard length of 22 mm, above which there were no females in this collection. The difference in the slopes of the regression lines suggests that longer females would also have shorter caudal fins than males of similar standard lengths. There was no difference between barred and/or colored males and those males without the pigments. The elevations of the regression lines were significantly different (Fig. 7), but the size difference was <1 mm. Males were found to have longer pelvic fins than females, but this was not due to differential elongation with increasing body length as seen with the dorsal and caudal fins. The elevation of the regression line for males was significantly higher than the line for females (Fig. 8), but the size difference was <1 mm. There was no difference between barred and/or colored males and those males without the pigments. The slopes of the regression lines were significantly different (Fig. 8), but there was no clear separation of the two groups in this size range. A subset of each group was chosen to measure variance in lengths of the dorsal HARRINGTON: D. PAUCIRADIATUS BEHAVIOR PA'ITERNS AND DIMORPHISM 879

o 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 Standard length (mm) Figure 5. Length-frequency distributions for all males and females of D. pauciradiatu~' included in the analyses of fin lengths (Figs. 6-8). Fishes were collected using a pushnet at site A marked in Figure I. These fishes are a subset of those shown in Figure 2, and their peak frequencies are at similar lengths to those seen in Figure 2.

and pelvic fins. The females were 16-23 mm (SL), the unbarred and uncolored males were 19-27 mIll (SL), and the barred and/or colored males were 22-28 mm (SL). The variances in length of the first dorsal fin were 0.14 (females), 13.4 (unbarred and uncolored males), and 11.4 (barred and/or colored males). The variances in length of the pelvic fin were 0.28 (females), 0.51 (unbarred and uncolored males), and 0.72 (barred and/or colored males). General Behavioral Account.-FEEDlNG. Individuals in the laboratory were observed feeding throughout the day, including periods between bouts of courtship and spawning. All feeding was upon benthic sources and consisted of the frozen brine shrimp added to the tanks as well as organisms living in the sand substrate. In the field, this species feeds primarily on harpacticoid copepods (Sogard, 1984), but it also feeds on other meiofauna living on blades of seagrass (pers. obs.). Individuals were observed to obtain prey items by extending the highly protrusible jaws and drawing the item into the mouth, often followed by an expulsion of sand. NIGHTACTIVITY.Individuals in the laboratory were observed to be either partially buried in the sand or resting on the surface of the substrate at night. Move- ments were infrequent and typically consisted of a sudden burst forward followed by burying in the sand. The sandy substrate in the aquaria may have made it harder for individuals to bury, since the silty sediments in seagrass beds (normal habitat) are more loosely packed. In the field, individuals have been reported to bury themselves in different locations nightly (T. Yoshikawa, pers. COmIll.). TERRITORIALITY.There was no evidence of site attachment by males or females in the laboratory or in the field. In addition, individuals did not defend specific areas of substrate from intrusion by conspecifics or individuals of any other fish species, even at the lowest densities. High densities may have prevented estab- 880 BULLETIN OF MARINE SCIENCE, VOL. 60, NO.3, 1997

10 FEMALES (y = 0.23x - 0.55; r2= 0.76; n = 169) 20 MALES (y 1.05x - 12.46; r2 0.85; n 147) :Z0 = = = :z --e El 15 cO -- 10° 0 19 'to 0 oQJ r::l o QJ 0 EP I 10 A -r::l 0 a:: IlJ 0 <:IS -~ 0 0 '0•.. 5 ~lJ) •...... •

0 8 10 1:z 14 16 18 :z0 :z:z :Z4 26 28 30 Standard length (mm)

10UNBARRED AND UNCOLOREDMALES(y = 1.29x - 18.11; r2= 0.73; n = 44) 20BARRED AND/OR COLOREDMALES (Y = 1.16x - 14.50; r2 = 0.79; n = 50) 20

--e e 15

~ r::l QJ I -r::l 10 tl:: ~ -lJ) ~ 0 '0 •.. 5 .•..'"~ \J.o

o 16 18 20 2:Z 24 26 :Z8 30 Standard length (mm)

Figure 6. First dorsal fin-length vs. standard length for D. pauciradiatus collected from Biscayne Bay, Florida. The slopes of regression lines for males and females (A) are significantly different (t test. P

2 10 FEMALES (y = 0.26x + 0.75; r = 0.72; n = 169) 140 20 MALES (y = O. 51x - 3.21; r2 = O. 80; n = 147)

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2 8 10 12 14 16 18 20 22 24 26 28 30 Standard length (mm)

10UNBARREJ) AND UNCOLORED MALES(y = 0.61x - 5.50; r2= 0.68; n = 44) 140 20 BARRED AND/OR COLORED MALES (y = O. 60x - 5.04; r2 = 0.66; n = 50)

12 El e '-' oS 10 B bO d CLI I -d «::: 8 -; 't:l ~ ~ 6 U

30 Standard length (mm)

Figure 7. Caudal fin-length vs. standard length for D. pauciradiatus collected from Biscayne Bay, Florida. The slopes of regression lines for males and females (A) are significantly different (t test, P<0.05), but there is no clear separation of groups at standard lengths in which the two sexes overlap (10-21 mm). When the above males are divided into those with mouth bars (barred) and/or orange pigments (colored) and those without these pigments (B), the regression lines are parallel (t test, P>0.05). The line for barred and/or colored males is significantly higher (1 test, P<0.05), though the difference is small « I mm). 882 BULLETIN OF MARINE SCIENCE. VOL. 60. NO.3. 1997

10 FEMALES (y = 0.25x - 0.12; r2 = 0.68; n = 169) 20 MALES (y = 0.27x - 0.28; r2= 0.86; n = 147)

8 o

-e e .s:l 6 be d Q.J A ,S-I tj..; u '> • -~Q.J

Standard length (mm)

10 UNBARREDAND UNCOLOREDMALES(y '" 0.32x - 1.13; r2 0.75; n 44) 9 = = 20 BARRED AND/OR COLOREDMALES (y = O. 23x + 0.95; r2 = 0.65; n = 50)

8 -e e 7 .cl +-'bO d Q.J 6 I -d i.i:: u 5 'S Q.J -~ 4 1

3 16 18 20 22 24 26 28 30 Standard length (mm)

Figure 8. Pelvic fin-length vs. standard length for D. pauciradiatus collected from Biscayne Bay, Florida. The slopes of regression lines for males and females (A) are parallel (t test, P>O.05). The line for males is significantly higher (t test, P

Ethogram.-LocOMOTION. Four types of swimming were observed. All swimming resulted in a forward motion with no lateral or backward motion. Burst swimming was accomplished by using the pelvic fins to first propel the body off the substrate and then to glide as the pectoral fins propelled the body forward (approx. lh body length). It was not accomplished by using the pelvic fins to push the body forward, as in the mudskipper, Boleophthalmus boddarti (Clayton and Vaughan, 1988). Individuals often remained on the substrate for approximately 1 sec before propelling forward again. This was the most common type of swimming and was used during foraging. Continuous swimming also used the pectoral fins to propel the body forward and the pelvic fins to lift and glide. The distance traveled (>2 body lengths) was much greater than with burst swimming. This swimming pattern was often used by males from the late afternoon to just before dark, when approaching a potential mate from a distance and during approach or retreat in an aggressive encounter. Rapid swimming differed from the previous two patterns by using the caudal fin as well as the pectoral and pelvic fins. The caudal fin likely provided the means to achieve rapid speed. This pattern was only observed during aggressive 884 BULLETIN OF MARINE SCIENCE, VOL. 60, NO.3, 1997 bouts when attacking or fleeing, or when individuals were disturbed by human actions. Vertical swimming was accomplished by using the pectoral fins to propel the body vertically into the water column, sometimes extending the dorsal fin as an apparent keel. Although the pelvic, caudal and dorsal fins were extended, they were held still while the pectorals propelled the body upward. This pattern occurred during spawning, but it was also observed when individuals ascended a piece of seagrass or the wall of the aquarium. MAINTENANCEPATTERNS.-Defecation: This occurred while stationary on the substrate. An individual would defecate by arching its body so the center of the ventral surface was raised above the substrate. The pectoral fins would then beat rapidly while a fecal pellet was expelled and subsequently propelled into the water column as high as 10 cm. The function of such expulsion is unknown, but it may aid in passing the large amounts of sand ingested along with prey items, or it could distance the fish from a fecal pellet that may attract predators such as blue crabs (Callinectes sp.). FEEDING.-Feeding occurred throughout the light hours and consisted of extending the highly protrusible jaws out and toward the substrate. Food items were drawn into the mouth (vacuum-like action), and inedible particles were then expelled. In the field, individuals were also observed to bite at epifauna on seagrass blades, jerking the head side to side to remove the organism from the blade. Gut content analyses of adult males and females revealed a large proportion of indigestible material (e.g., sand) concentrated in the hindgut. Qualitative observations of prey items confirmed that harpacticoid copepods, ostracods, and mites are the three most abundant groups (Sogard, 1984). Ten males and females were preserved in 70% ethanol immediately upon capture, and gut contents were examined within 1 h of preservation, allowing coloration of prey items to be as- sessed. All copepods, ostracods, and mites were observed to have orange pigmentation, and the orange color appeared to match (under artificial light) the orange pigments found in males of D. pauciradiatus. COURTSHIPANDSPAWNING.--Courtship was observed throughout the day but increased in the evening. Spawning only occurred during the 2 h before dark. The sequence of behaviors leading to spawning was always as follows: approach -7 lateral display -7 close swim -7 locking -7 spawning. Thus, patterns are described in order of their occurrence. A flow chart shows the possible outcomes of male- female encounters as well as an indication (qualitative) of path frequencies (Fig. 9). Courtship and spawning, in both the field and laboratory, occurred only in open sand patches and not in dense seagrass. Approach: This involved oriented movement (typically continuous swimming) toward a potential mate. The approach was primarily performed by males, although females occasionally approached males during the two hours before dark, typically after a spawning ascent in which eggs were not released. Courtship lateral display: This was performed exclusively by males and directed toward females. It involved extending the first and second dorsal, caudal and pelvic fins, while the pectoral fins were used to propel the male forward during the display. This was the only courtship pattern in which males raised their first dorsal fins. The mouth was opened, and the mouth bar (if present) and eye bar were shown (Fig. 3). The pelvic fins remained in contact with the substrate while the posterior end of the body moved side to side in a wagging motion. This often resulted in sand being stirred into the water column. The first dorsal fin was tilted toward the female such that it extended above the female's body (Fig. 3). HARRINGTON: D. PAUC1RAD1ATUS BEHAVIOR PATTERNS AND DIMORPHISM 885

Approach (m, f)

! Avoidance (f) Lateral display (m)

~ ~ Parallel swimming Chase (m)

Locking+

Ascent into !ter column ,/ 1 Spawning ---) SeparationJ, (--- Interference (m) Return to substrate Figure 9. Courtship behavior flow chart for D. pauciradiatus. The thickness of the arrows indicates the relative likelihood that the following behavior will occur. (m) = performed by males. (f) = performed by females.

The display was almost exclusively performed while in a parallel orientation to the female. Close swim: This was performed by the pair only if the female did not flee the male after courtship lateral displays. The female turned toward the male, and the pair moved together in either burst or continuous swimming while close together. This was followed by locking if the pair was not interrupted by another male. Locking: This occurred when the male and female came into contact while close swimming. Both nudged each other until their pelvic fins were in an interlocking arrangement. The interlocking of the pelvic fins was essential for spawning to occur, as pairs returned to the substrate whenever unlocking occurred. Spawning: While in the locked position, the pair moved vertically into the water column (Fig. 3). The only fins moving were the pectorals, although the pelvic, anal, caudal and second dorsal fins were extended. The male was often below the female at an approx. 45° angle and appeared to lift the female into the water column. The pair continued up into the water column until they released gametes (often coinciding with an inward curling of the body) or broke apart before gamete release. In either case, the pair separated and each individual glided or darted back to the substrate separately. When gliding, females would raise their first dorsal fins, apparently as a keel, during descent. If gametes had not been released, the pair approached one another and, once again, began the process with parallel swimming. This continued until spawning ceased for that pair. Pairs were observed to perform at least four ascents without the release of gametes (confirmed with net), followed by additional ascents, after 886 BULLETIN OF MARINE SCIENCE, VOL. 60, NO.3, 1997 which fertilized eggs were collected. Pairs have not been observed performing multiple ascents in the field, and females typically buried themselves upon descent (T. Yoshikawa, pers. comm.). AGONISTICBEHAVIORS:(performed exclusively by males).-Approach: This was performed using burst or continuous swimming. The male oriented toward a male or female. If the other individual was moving, the approaching male would alter its course toward a point ahead of the other. Males were successful at turning away other males by an approach at the proper angle. This type of approach may be a more energy efficient behavior than a chase or lateral display (detailed below). Agonistic lateral display: This was only directed at other males and resulted in their fleeing or displaying in return. Unlike the display during courtship, this was conducted in the anti-parallel orientation (head to tail). Like the courtship display, all fins were extended, and the mouth was opened showing the mouth bar (if present). The eye bar was also noticeable (Fig. 4). The pelvic fins became dark, while the anal and the ventral half of the caudal fin showed multiple rows of dark spots. A bout of displaying typically began with a wagging motion similar to that seen during courtship displays. The first dorsal was tilted toward the opponent such that it extended over the opponent's body. Circling: This occurred when both males displayed. They typically assumed a display posture different from courtship. The body was arched so the head and tail regions were higher above the substrate than the pelvic region. They then hovered above the substrate and circled each other with all but the pectoral fins extended and motionless (Fig. 4). The pectoral fins were used for propulsion. Parallel swimming: This occurred when both males swam together (burst or continuous) after a bout of circling or another bout of parallel swimming. This was sometimes performed while both males were in the arched posture described above. It was terminated when one male turned so that the pair was anti-parallel. At that point, lateral displays commenced again. Head twitch: This was defined by high frequency, small amplitude lateral movements of the head performed by one or both males during pauses between bouts of circling or parallel swimming. This was only observed in cases when the two interacting males were of similar size or rank and after many bouts of displaying had occurred. Twist contest: This was a highly aggressive action pattern that occurred after extended bouts of lateral displays between males and often after head twitching. The males spun rapidly around each other, presumably in an attempt to bite each other. Eventually, one male fled, followed rapidly by the victorious male. Preopercular spine bite: This involved two males approaching each other head on, each attempting to bite the other's preopercular spine. If both males had hold of the other's spine, a twist contest would often ensue. Chase: This involved rapid swimming toward another individual that was moving away. Often, the chase ended with a nip. Chasing occurred throughout the day, but its frequency increased in the two hours before dark. Nip: This behavior was followed a chase and consisted of a single bite. Nips were observed most often in the two hours before dark, except when males were newly introduced into colonies. Nips directed at the first dorsal or caudal fin were observed to cause damage (Fig. 4). Aggressors were observed holding dorsal spines in their mouths while the other males attempted to flee. This resulted in the aggressors being pulled around the aquarium until the fin was tom or the males released their hold. Interception: This involved rapid swimming into the water column toward a HARRINGTON: D. PAUCIRADIATUS BEHAVIOR PATIERNS AND DIMORPHISM 887 spawning pair. The male would hit the spawning pair, resulting in their breaking apart from the locked position, and this resulted in the pair returning to the substrate. In the aquaria, such aggression was always directed at the male. In both the field and laboratory, the pairs were intercepted while still close to the substrate «20 cm), thus streaking (Warner and Schultz, 1992) was likely not the intention of the intercepting male. Open mouth: When approaching another male, a dominant male would fully open the mouth at which time the mouth bar was highly visible and in a direct line to the eye bar. The duration of such displays was 1-3 seconds. It was often accompanied by the raising of the second dorsal fin and a spreading of the caudal fin. MISCELLANEOUSPATIERNS.Fin waving: Females would raise their first dorsal fin and move it side to side, during which the body remained motionless. If the second dorsal fin was raised, it was at an angle of -30°. This behavior was observed in both the field and laboratory, and it was most commonly seen when objects or people approached the female. It was also performed in response to loud sounds. This is likely an anti-predation response (camouflage or seagrass mimicry) and/or pre-flight response, though it may be used by males or other females as a signal. Fin raising and waiving were also performed by young males «15 mm). This behavior was also observed in females and young males of Callionymus lyra (Holt, 1898). Rocking: This was similar to the above behavior in that both dorsal fins were raised, but in this case, the fins remained motionless while the body was arched so that the head and tail regions were above the substrate. The body was then rocked using the pelvic fins. This may also be an anti-predation response (seagrass mimicry). Burying: This was accomplished by using the pelvic fins to make a depression in the substrate into which the body was moved. Although males and females buried themselves (head partially exposed and gill openings exposed) at night, males were observed, in both the field (T. Yoshikawa, pers. comm.) and laboratory, to bury themselves upon the approach of a more dominant male. This resulted in an absence of additional aggression by the dominant male, and the subordinate male came out of the sand only after the dominant male moved away. Sounds.-A hydrophone was placed in a colony tank, and colonies were monitored for sound production during aggressive and courtship behaviors. No bio- genic sounds were detected. Sounds produced by males biting others and rubbing against the substrate during displays were not thought to be communicative in function.

DISCUSSION Sexual Dimorphism.-Descriptions of most dragonet species are derived from a limited number of preserved specimens. This can lead authors to make incorrect assumptions and underestimate the degree of sexual dimorphism. For example, published reports of sexual dimorphism in D. pauciradiatus are based on the descriptions by Davis (1966). Although the morphometries are undoubtedly ac- curate, the material consisted entirely of preserved specimens. Thus, the color patterns described are limited to those remaining after preservation. Personal observations of individuals before and after preservation indieated that melano- phores retain their dark coloration, while other chromatophores fade beyond recognition. Therefore, the mouth bar remains intact, but the orange and iridescent 888 BULLETIN OF MARINE SCIENCE. VOL. 60. NO.3, 1997 blue pigments soon fade out. This may explain why Davis notes the mouth bar, but makes no mention of the latter two pigments. Another inconsistency with the present study is the description of the first dorsal fin from Davis (fig. 3, p. 843). The drawing of an adult male shows the four spines to be connected except for the last -10%. In fact, in all males examined in the present study, the tissue connecting the spines extended only about 25% of the way (-1,2 the length of the second dorsal fin-rays). The pigment pattern and shape of the connecting tissue are also inaccurate in the former study. These tissues are easily torn when examining the spines, and it is likely that Davis assumed the tissue extended farther but was torn. In addition, I found the fourth spine to be as long as the third spine and not as short as was depicted by Davis. This could be explained by possible damaged specimens. With respect to the length of male dorsal fin-spines, Davis described some spines extending half-way out on the caudal fin when lying along the body (p. 847). Among the 600 males examined in this study, none had a dorsal fin that extended past the caudal peduncle. It may be that only older males develop such long fins, and these males were not present in this study's collections. The specimens used by Davis came from many locations, and range-specific differences may exist for this character. Also, dorsal fin-spines may be shortened in length if bitten during male-male aggression. Broken spines may account for some of the variance in length of the dorsal fin measured in males. As some theories predict (Pomiankowski and M\1l11er,1995), the variance in an apparent sexual trait (dorsal fin) is higher than in a non-sexual trait (pelvic fin). In addition, the same trait (dorsal fin) in females shows much lower variance than in males. This suggests that the exaggerated first dorsal fin in males of D. pauciradiatus may have evolved through directional sexual selection (Pomiankowski and Ml1Iller,1995). Subsequent experiments indicate that the length of the first dorsal fin in males affects the outcome of both female mate choice and male- male competition (Harrington, 1996). Although smaller males have a pigmented first dorsal fin like that of females, these pigments disappear as the males get larger. The common color pattern in small males and females suggests a common function, possibly enhanced cryptic coloration. Subjects raised the dorsal fin in response to loud noises and upon the approach of people both in the laboratory and field. The fin waved back and forth in a manner that resembled the movement of surrounding seagrasses. As males grow and the dorsal fin elongates, this possible function of seagrass mimicry may be outweighed by other factors such as visibility to predators during lateral displays. Davis (1966) also notes that D. pauciradiatus is the only western Atlantic callionymid species (all within the genus Callionymus at the time) possessing ventral pigmentation (only in males). Considering more recent revisions of the family Callionymidae (Robins and Ray, 1986), this is not so surprising. There may be as many as seven species in the western Atlantic (C.R. Robins, pers. comm.); however, the genus Diplogrammus is still considered monospecific in this study's region. In a description of another species in the genus Diplogrammus (D. xenicus), Fricke and Zaiser (1982) noted the presence of ventral pigments in males only. This pigment pattern may be common to all members of the genus. Given the location of these pigments and the benthic habitat of these fishes, the function, if any, of such pigmentation is not immediately obvious. The only time these pigments are exposed is during spawning, and both males and females are subject to similar exposure. Fricke and Zaiser (1982) also describe a ventro-lateral fold of skin below the HARRINGTON: D. PAUClRADIATUS BEHAVIOR PATIERNS AND DIMORPHISM 889 lateral line extending from the first anal fin ray to the caudal peduncle. This same structure is called a ventrolateral keel by Davis (1966); the character upon which the genus is named. During the present study, thin sections were taken from an adult male and female, and microscopic analysis (blue color, hemotoxylin stain) revealed that, for D. pauciradiatus, this keel contains a cartilaginous structure (M.e. Schmale, pers. comm.). Although its function remains unknown, the structure and location (resting just on the substrate) suggest a possible role in the detection of particle motion (vibration). This, in turn, may aid in predator avoidance. Because this structure is not sexually dimorphic, any hypothesis as to its possible function should apply to both sexes. One final observation of note refers to the caudal fin of the male shown in Figure 4. The present study involved the collection and measuring of over 600 males of D. pauciradiatus, and this is the only male observed to have elongated caudal fin rays. Davis (1966) also did not report any such finding. The caudal fins of some males appeared shorter than expected, and observations under a dissecting microscope revealed evidence of aggression (i.e., bitten rays). This is one possible explanation for finding only one male with such a caudal fin. Another possible explanation is a genetic mutation resulting in differential growth of caudal filaments. Other members of the family Callionymidae have males with elongated caudal filaments, one of which, Foetorepus agassizi, is found in deeper waters within the same geographical range as D. pauciradiatus (Robins and Ray, 1986). The elongated fin ray may have evolved in response to sexual selection via male-male aggression or female choice. Agonistic Behavior.-Behavioral descriptions of D. pauciradiatus are limited to those in Sogard's (1982) thesis. Although the lateral display of the males was mentioned, courtship and agonistic displays were not distinguished. For example, darkened pelvic fins were described as a courtship coloration (p. 84), while I have observed this to be an aggressive color pattern to which females were unreceptive. Also, a " ... flaring of the preopercular spines ... " (p. 84) was described as part of the lateral display. During the display, the mouth and gill openings were open, causing the preopercular spines to move outward to some degree. The spines were not independently moved into a flared position during any displays. Sogard's observations were made while housing subjects for feeding experiments, and behavior was not the focus of the study. Accounts of the motor patterns associated with agonistic encounters in dragonets are limited to Holt's (1898) and Wilson's (1978) papers on the behavior of Callionymus lyra held in large aquaria. From their descriptions and the photo- graphs provided, it appears that males of this species are territorial and more aggressive than D. pauciradiatus. They are similar, however, in the darkening of the pelvic fins during agonistic encounters, the existence of dominance hierarchies, and (perhaps) the presence of pigments similar to the mouth bar. Males were also observed to bite opponents' dorsal fins during fighting (Wilson, 1978). This differed from D. pauciradiatus in that the fins were bitten while erected, a behavior never observed in males of D. pauciradiatus. Holt described a motor pattern similar to interception, but the actor was unsuccessful in disrupting the spawning event. Wilson proposed that Holt's (1898) original descriptions of behavior did not mention territoriality because the fish were held in smaller aquaria at higher densities, thus preventing the establishment of territories. Neither Wilson nor Holt mention female agonistic behavior, and it may be that females of C. lyra are similar to females of D. pauciradiatus in that regard. Although their main focus was on the spawning behavior of Callionymus en- 890 BULLETIN OF MARINE SCIENCE, VOL. 60, NO.3. 1997 neactis. Takita et at (1983) mention some aspects of male behavior from which tentative conclusions can be drawn. Six males and 14 females were held in a round colony tank, and spawning activity was monitored at night using a "faint light" over the tank. They report that only two of the six males spawned. The two spawning males occupied separate halves of the tank and did not enter the other male's half of the tank. Non-spawning males intercepted spawning pairs by striking at them in the water column. Daytime observations recorded intense fighting between males involving biting each other's mouth and twist contests as seen in D. pauciradiatus. They also mention that similar fights have been documented in the field for C. enneactis. Based on the above descriptions, males of C. enneactis are apparently territorial, at least during spawning hours. Additionally, it appears that they form dominance hierarchies, and that the most dominant males are the ones that obtain spawns. They appear to differ from D. pauciradiatus in that the only aggression observed during spawning hours was interception. Males were not aggressive toward each other except during the daytime. In D. pauciradiatus, males were most aggressive toward other males during spawning hours. This may be due to the difference in light availability or to the fact that females of C. enneactis are buried until moments before spawning. No agonistic interactions between females were observed. Courtship and Spawning Behavior.-Published accounts of the motor patterns associated with courtship and spawning in dragonets are also few, but the descriptions are generally more detailed than is the case for agonistic behaviors. Takita and Okamoto (1979) observed spawning by Callionymus flagris and C. richardsoni in aquaria, and they characterized spawning as having four phases: courtship, pairing, ascending, and releasing of gametes. The authors suggested that a male's elongated first dorsal fin is a character preferred by females, and that it also serves in species and sex recognition. Although their description of courtship is limited, behavior patterns appear to be similar to those of D. pauciradiatus, with the following exceptions: pairs ascend into the water column only once (at which time gametes mayor may not be released), and females spawned once daily for at least 3 days. Males spawned more than once per day and for consecutive days. Spawning for both species occurred in the hours before sunset. Takita et al. (1983) reported that C. enneactis differs from other dragonets in that it spawns at night. In the laboratory, all individuals buried themselves at dusk, but the males began moving about the bottom approximately 90 min later. Females then also came out of the substrate and the pair immediately began an ascent into the water column. The spawning ascents were short (-5 sec) compared to that of D. pauciradiatus, which can take as long as 30 sec. Females apparently made only one ascent per evening, and the authors suggested that females spawned for seven consecutive days. Males, on the other hand, completed multiple spawnings in each evening. If a pair was intercepted by a second male, the female was not immediately approached again by the male, as was seen in D. pauciradiatus. Although spawning took place at night, courtship occurred during the day. The lateral display of males is not well described, but it appears to be of relatively short duration. A behavior similar to close-swimming also occurred during day- light hours. Holt (1898) described the spawning behavior of C. lyra. From his accounts, it appears that the females spawn on many consecutive days. Females did not spawn with males lacking certain pigmentation patterns and dorsal fin development, but they mated indiscriminately among males with these traits, regardless of the HARRINGTON: D. PAUCIRADIATUS BEHAVIOR PATTERNS AND DIMORPHISM 891 male's rank:in the dominance hierarchy. Thus, dominance is not an apparent factor in determining male mating success. Unlike D. pauciradiatus, males of C. lyra will perform lateral displays while some distance from any other individuals. Finally, males were observed biting the raised dorsal fin of other males. If the elongated dorsal fin is a character preferred by females, reducing the size of competing male's fins may enhance an individuals chance of obtaining spawns. The courtship sequence of C. lyra appears similar to that of D. pauciradiatus with some exceptions. It is unclear from Holt's (1898) description whether or not lateral displays included any side-to-side motion like the wagging described for D. pauciradiatus. Motor patterns similar to close-swimming and locking preceded the pair's ascent into the water column, and the male was often positioned un- derneath the female. All fins (except the first dorsal) were extended, as in D. pauciradiatus. Since only one female spawned during the observation period, multiple male spawnings were not possible. The female spawned with multiple males, but this may be an artifact of captivity. Finally, spawning in C. lyra occurred between 09:00 and 11:00. Holt (1898) mentions color patterns as possibly influencing female choice of mates, but no further details are provided. This is also the only mention of color patterns in any behavioral descriptions of dragonets. In D. pauciradiatus, the intensification of pigmentation during courtship and aggression suggests a possible function of color patterns in both male-male competition and female choice. During agonistic encounters between males of D. pauciradiatus, fins become darkened and can remain that way throughout the encounter. In contrast, only the orange pigments on the head and the mouth bar are intensified during courtship, the former often becoming reduced when the spawning pair enters the water column. This reduction, combined with a lack of fin pigmentation, may make the spawning pair more cryptic, thus reducing the chance of predation during this vulnerable period. The need to remain cryptic may also account for the sudden onset of pigmentation, exposing the male only when necessary. Future descriptions of dragonet behavior should include color patterns so comparisons can be made between species living in different habitats with different predators. Published observations of spawning in the field are still lacking for any species of dragonet, and all observations made of D. pauciradiatus spawning were made in open sand flats (T. Yoshikawa, pers. comm.). The above hypotheses regarding cryptic coloration predict that pairs of D. pauciradiatus, spawning in seagrass beds, may limit their ascent to the height of the seagrass. This could result in decreased exposure to predation while allowing the eggs to disperse beyond the seagrass. The two grasses dominating the areas from which subjects were collected, Thalassia testudinum and Syringodium filiforme, each reach lengths of 30 cm (Kaplan 1988). In the large aquaria (62 cm deep), spawning pairs typically released eggs after ascending 30-40 cm into the water column. Furthermore, females held in 15 cm deep water did not release eggs during multiple spawning ascents, suggesting a possible minimum height above the substrate is required for spawning. Field observations are needed to confirm the height of spawning pairs relative to the height of the seagrass and the likelihood of predation. Most studies have not included data regarding the development of eggs after fertilization, but Takita (1983) described embryonic and larval development of Cal/ionymus cal/iste. The larvae hatched 11 h after spawning when held in -290 C water. This is similar to the hatching time of D. pauciradiatus (14 h), considering the temperature difference (290 vs. 260 C). This temperature difference may also account for the earlier development of a functional mouth by C. cal/iste (48 vs. 72 h). 892 BULLETIN OF MARINE SCIENCE. VOL. 60. NO.3. 1997

As expected, a number of similarities exists among the motor patterns of dragonets studied to date. The brevity of previous studies unfortunately precludes detailed behavioral comparisons. Dragonets have been collected from a wide va- riety of habitats, and adaptations may well exist that lead to different motor patterns associated with courtship and agonistic behaviors. Those dragonets studied to date all spawn in the water column, but the time of spawning varies from early morning to well after sunset. The above variations may allow testing of hypotheses regarding the adaptive nature of observed reproductive strategies and the importance of sexually dimorphic traits to male spawning success.

ACKNOWLEDGMENTS

I thank A. A. Myrbcrg Jr. for his guidance throughout this study, and I thank M. Schmale, M. Ryan, R. Tokarz and S. Green for their critical comments on the manuscript. I thank J. Stadler, M. Edmonds, M. Rose, A. Almanza, and D. de Sylva for their assistance with field collections. Financial assistance was provided by the Bader Fund and "Anonymous Donor in MBF" at the University of Miami. I thank T. Yoshikawa for sharing her observations of dragonets in the back reefs of Puerto Rico. Finally, I would like to thank C. R. Robins for serving on my Ph.D. committee even after his retirement. I have benefited from his vast knowledge and have been inspired by his devotion to integrity in science.

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DATEACCEPTED: July 9, 1996.

ADDRESS: (M. E. H.) Rosenstiel School of Marine and Atmospheric Science, Marine Biology and Fisheries, 4600 Rickenbacker Cswy., Miami, FL, 33]49.