785
Abstract.-Three species of the Temporal and spatial spawning stromateoid genus Peprilus have been found to occur in the northwest Atlan patterns of the Atlantic butterfish, tic: P. triacanthus Ibutterfishl, P. burti (gulf butterfish), and P. alepidotus Peprilus triacanthus, in the South (harvestfish). Peprilus triacanthus and P. alepidotus reportedly spawn from and Middle Atlantic Bights* May through August and June through July. respectively. Peprilus burti spawns twice yearly: Februarythrough May and Teresa Rotunno September through November. Collec tions oflarvae andjuveniles ofPeprilus Robert K. Cowen spp. from the northern South Atlantic Marine Sciences Research Center (SAB) and Mid-Atlantic (MAB) Bights State University of New York during both the spring and summer of Stony Brook, New York I J 794-5000 1988 and 1989 suggest that either a E-mail address (for T. Rotunno): [email protected] combination of species was spawning or that reported spawning dates were suspect. Species identification of Peprilus in these collections was deter Three species of the stromateoid ing the winter and early spring mined with morphometric, meristic, and pigment character analyses. Speci genus Peprilus (order: Perciformes) (Horn, 1970). Spawning by P. burti mens sampled had counts for caudal are reported to occur in the west is reported to occur during two dis vertebrae (18-19) and ventral midline ern North Atlantic: butterfish, P. tinct periods, February through May melanophores (11-16) consistent with triacanthus (Peck), gulfbutterfish, and September through November those found for P. triacanthus in previ P. burti (Fowler), and harvestfish, (Murphy, 1981). Unlike these other ous studies. By analyzing otoliths, we P. estimated larval and juvenile growth P. alepidotus (Linnaeus). Although two species, alepidotus does not rates to be approximately 0.23 mmlday. the ranges of all three species ex exhibit seasonal migration patterns, Backcalculation ofhatch dates suggests tend along the eastern coast of remaining in shallow waters either two spawning events for P. NorthAmerica and the West Indies, throughout theyearwhere itspawns triacanthus, February through mid there is some question as to which during June and July (Horn, 1970). April and mid-May through late July, orone extended spawning period begin species ofPeprilus are regular resi During the spring and summer ning in late February and ending in late dents in the South Atlantic Bight seasons of 1988 and 1989, we con July. This study reveals that P. tria (SAB) and Mid-Atlantic Bight sistently collected larval and juve canthus spawnsfor a much longer period (MAB) regions (Caldwell, 1961; nile Peprilus from the South Atlan than previously thought. It is possible Haedrich, 1967; Horn, 1970; Persch tic and Mid-Atlantic Bights. The that P. triacanthus spawns during the spring in the SAB and summer in the bacher et aI., 1979). This question combination of their location and MAB as a strategy to extend the dura is extended by the suggestion of dates ofcapture raised the question tion ofits spawning period. This strat possible hybridization between P. as to which species were present in egy is one used by other north-south triacanthus and P. burti in the our samples. Although most abun migrating species and warrants further northern portion ofthe SAB (Horn, dant within the MAB region, P. study. 1970; Perschbacher et aI., 1979). triacanthus is reported to spawn Reproduction in P. triacanthus during the summer only (Horn, and P. burti is seasonal and appar 1970). According to time ofcapture, ently associated with annual migra the spring-collected larvae in our tion patterns (Horn, 1970). In the SAB samples should have been P. summer and fall, P. triacanthus burti because they were collected be migrates northward and inshore, fore P. triacanthus and P. alepidotus where it reportedly spawns from supposedly begin to spawn (Horn, late May through August, with a 1970; Murphy, 1981). However, their peak in June (Horn, 1970). During occurrence within the SouthAtlantic winter, P. triacanthus migrates off and Mid-Atlantic Bights suggests shore and becomes horizontally re thatthey were eitherP. alepidotus or stricted (Horn, 1970). Movement by P. triacanthus. Thus, the overall aim P. burti is somewhat opposite to that ofthis study was to identify the spe ofP. triacanthus. Peprilus burti mi cies in our samples and to back- grates offshore during late spring * Contribution 1061 ofthe Marine Sciences Manuscript accepted 7 March 1997. through early fall, then onshore to Research Center, State University ofNew Fishery Bulletin 95:785-799 (1997). wards shallow bays and inlets dur- York. Stony Brook, New York 11794-5000. 786 Fishery Bulletin 95(4), J997 calculate hatching dates by using validated otolith-increment analysis.
Materials and methods
Collections
PeprilU8 larvae and juveniles were collected during April and May of 1988 and April of 1989 in the northern SAB, offshore of Cape Hatteras, North Carolina, and June-August of1988 and 1989 in the MAB, from Long Is land, New York, to Cape May, New Jersey (Fig. 1; Table 1). Fish were collected with a 1-m2 Tucker trawl and a 5-m2 Frame trawl. The Tucker trawl had three opening-closing 505-J.l.m mesh nets. Five-minute tows were taken at three primary depth intervals: 0-5 m, 5-10 m, and 10-15 m. For the purpose of this study, all depths were combined. The Frame MAS trawl was fitted with a 2-mm mesh net and - -- towed at the surface for 10 minutes. A flow SAB meter was attached to each net to estimate the volume ofwater sampled. Tucker trawl samples were split in half with a Folsom plankton splitter. One halfof each sample was preserved in 5% buffered 74° formaldehyde and used for identification and L..JL-__L-__.LI__----I.I__--' L..-__-L-_-----' length and body depth measurements. The otherhalfwas preserved in 95% ethanol and Figure 1 used for otolith analysis. Frame samples Study areafrom CapeHatteras, NorthCarolina, to Long Island, New York. were preservedin95% ethanol. Samples were Dotted and barred areas represent spring and summer sampling areas, sorted in the laboratorywith a dissecting mi respectively. croscope for eggs, larvae, and juveniles. by calculating regressions ofbody depth on standard Morphometrics length as a function ofstandard length.
Determination of a seasonal difference in body size Meristics was accomplished by analyzingbody depth (BD) and standard length (SL) for all specimens collected. To determine the species composition of the spring Measurements were made to the nearest 0.1 mm with and summer-collected Peprilu8 larvae, two meristic eithera video-enhanced digitizing system(Optical Pat characters were examined: number ofcaudal verte ternRecognition System, BIOSONICS, Inc.) oran ocu brae and number of ventral midline melanophores. lar micrometer. Standard length was measured from Charactercounts were compared withpublished data tip ofthe snoutto the tip ofnotochord. Body depth was for each of the three possible species (caudal verte measured perpendicular to the longitudinal.body axis brae: Ditty, 1981; ventral midline melanophores: atthe anterior marginofthepectoralbase (Ditty, 1981). Dittyand Truesdale, 1983). Subsamples ofspecimens To examine differences in body depth between were either cleared and stained (Taylor, 1967; spring and summer seasons, linear regressions of Wassersug, 1976; Dingerkus and Uhler, 1977; body depth on standard length were calculated for Potthoff, 1984) or x-rayed (Gosline, 1948; Miller and Tucker and Frame cruises, 1988 and 1989. Slopes of Thcker, 1979; Thcker and LaRoche 1984; Kosenko et regression lines were tested for homogeneity. Allom aI., 1987). Photomicrographs of cleared and stained etric effects ofgrowth on body depth were examined specimens were taken and slides developed for further Rotunno and Cowen: Temporal and spatial spawning patterns of Peprilus triacanthus 787
Table 1 List of 1988 and 1989 cruises, sampling dates, number offish collected, and locations. SAB =South Atlantic Bight; MAB =Mid Atlantic Bight.
Net Cruise Date No. offish captured Location
1988 DEL88-5-2 24 April-l May 71 SAB Frame ATLANTIC TWIN 21 May-23 May 29 SAB DEL88-7-1 1 June-3 June 3 MAB DEL88-7-2 11 June-16 June 22 MAB DEL88-7-3 6 July-9 July 4 MAB DEL88-7-4 16 July-22 July 99 MAB DEL88-7-5 29 July-2 August 50 MAB DEL88-7-6 8 August-12 August 110 MAB Tucker DEL88-7-3 6 July-9 July 188 MAB DEL88-7-4 16 July-22 July 1,191 MAB DEL88-7-5 29 July-2 August 514 MAB DEL88-7-6 8 August-12 August 1,063 MAB 1989 Frame FE1-89 25 April-29 April 158 SAB ONRI-89 30 May-2 June 8 MAB ONR2-89 6 June-7 June 4 MAB FE2-89 7 July-l0 July 2 MAB ONR4-89 18 July-2 August 22 MAB ONR5-89 14 August-18 August 170 MAB Tucker FE1-89 25 April-29 April 201 SAB FE2-89 7 July-l0 July 445 MAB ONR4-89 18 July-2 August 89 MAB ONR5-89 14 August-18 August 146 MAB inspection. Fish were x-rayed with a Kodak. Faxitron Otolith marking experiment atsettings of40 kilovolts, 20 milli-amperes and 30 sec onds, which gave the best results with Kodak. Industry Otoliths of22 fish were marked with oxytetracycline X negatives. These negatives were placed in a Kodak. hydrochloride (OTC) inAugust of1991 to determine GBX developer and replenisher solution for 2 to 3 min ifPeprilu8 larvae and juveniles deposit daily rings. utes, rinsed in water, placed in a Kodak GBX fixer so Sizes offish ranged from 10 to 31 mm SL. Fish were lution for 5 minutes, rinsed for 15 minutes in water, acclimated for two days in a five-gallon bucket with and dried overnight. Caudal vertebrae were counted built-in screeningthat allowed waterto flow-through with the aid of a dissecting scope and included those the bucket when it was placed in an aerated seawa vertebrae attachedto the first fully formed hemal spine ter bath. Fish were fed twice daily with either live and extending to the urostyle
1 Secor, D. H .• E. D. Houde, and D. M. Monteleone. 1995. 2.0 per haul) through mid-August (n=110; 2.2 per Development of otolith-marking methods to estimate survival haul) inthe MAD. Frametrawlsfor 1989 had the great and growth ofearly life stages ofnatural and hatchery-produced est abundances oflarvae during lateApril (n=158; 4.3 striped bass in the Patuxent River in 1991. Maryland Depart ment of Natural Resources, Chesapeake Bay Research and per haul) in the SAD and from mid-July through early Monitoring Division, CBRM-GRF-94-1. 145 p. August in the MAD (n=170; 4.4 per haul). Rotunno and Cowen: Temporal and spatial spawning patterns of Peprilus.triacanthus 789
50 Frame 1988 50 Frame 1989 _ Spring _ Spring 40 c:=J Summer 40 c:::::::::J Summer n=388 n=364 30 30
20 20
10 10 A B o 0
1000 -.------, 1000 Tucker 1988 (summer only) Tucker 1989 800 c:::::::::J Summer 800 _ Spring n= 2,984 c:::::::::J Summer 600 600 n= 881
400 400
200 200 c D o 0 l o 5 10 15 20 25 30 35 40 45 50 55 o 5 10 15 20 25 30 35 40 45 50 55
Standard length (mm) Figure 2 Length-frequency histograms for Peprilus triacanthus collected by net during the spring and summer of 1988 and 1989.
Morphometries stratedthatbody depth increases allometrically with respect to standard length up to a size of 10 to 15 A wide range ofsizes ofPeprilus were collected dur mm SL (Fig. 4). Body depth subsequently remained ing both seasons of1988 and 1989. Because size-fre about 50% oflength for each year. quency distributions had the same mode on all cruises within a season, length frequencies were combined for Meristies all fish sampledwith a particulargearduringeach sea son eachyear. Spring-collected 1988 fish ranged insize Ninety-nine percent of the fish collected with the from 6 to 43 mm SL (Frame; Fig. 2A). Similar size dis-. Frame net in 1988 and 1989 had either 18 or 19 cau tributions offishwere found for the 1989 springcruises: dal vertebrae (of those, approximately 90% had 19 4.7 to 37.5 mm SL (Frame; Fig. 2B) and 2 to 6 mm SL caudal vertebrae; Table 3). Counts ofeither 18 or 19 ('fucker; Fig. 2D). The 1988 summer trawls collected caudal vertebrae are consistent with those reported fish between 5 and 29 mm SL (Frame; Fig. 2A) and 1.3 for P. triacanthus (Table 3). The number of caudal to 36.0 mm SL ('fucker; Fig. 2C). Summer 1989 fish vertebrae was not related to body depth. According rangedin size from 6.0 to 50.0 mm SL (Frame; Fig. 2Bl to Ditty and Truesdale (1983), juvenile P. burti and and 1.7 to 49.0 mm SL ('fucker; Fig. 2D). P. alepidotus have mean body depth-standard length Deep- and shallow-bodied fish were identified from ratios of greater than 0.557 and caudal vertebrae both the spring and summer samples in both years. counts of17-18. However, our findings indicate that Fish had BD-SL ratios ranging from 0.119 to 0.750 fish with high body depth-standard length ratios also (Fig. 3, A and B). There was an indication of two had 19 caudal vertebrae. modes duringboth spring and summerof1989. These The fish we sampled had between 8 and 16 ventral BD:SL ranges overlap with ranges reported by Hom midline melanophores. Ditty (1981) reported ranges of (1970) and Ditty (1981) for all species (Table 2). Fur 4 to 8 ventral midline melanophores for P. burti and 11 ther analysis ofbody depth: standard length demon- to 17 for P. triacanthus. Seventy-sixpercentofourspeci- 790 Fishery Bulletin 95(4). 1997
1200 1988 _ Spring 1000 c:::::::::J Summer n=3.372 800
600
400
200
CD A .c E 0 InIL z::I 1200 1989 _ Spring 1000 c::::::J Summer n= 1,245 800
600
400
200 B O+--.----4...... e,----,-...... ,--..9""~_,______,-_r_____i 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
Body depth to standard length ratio
Figure 3 Body depth to standard length-frequency histograms for Peprilus triacanthus collected during the spring and summer of1988 and 1989. Frame- and Thcker-trawl collections were combined.
mens sampled had 11 to 17 ventral midline melano slope ofthe regression <0.921) did not differ signifi phores, and 94% had 10 to 16 melanophores. These cantly from unity (t-test: t=0.82, P=0,42). data suggest the presence of P. triacanthu8 in our samples. On further analysis ofpigment patterns, we Growth and hatching date found no difference amongspecimens (Rotunno, 1992). These data corroborate our caudal vertebral counts. Spring and summer growth rates were estimated from 1988 collections of Peprilu8 at 0.233 mm/day Otolith marking experiment and 0.219 mm/day, respectively. These growth rates were not significantly different (F=2.071, P=0.155). Daily increment formation was a valid indicator of Therefore, seasons were combined and an overall age ofPeprilu8 spp.. The presence ofsubdaily incre regression was computed that yielded an average ments was also noted in these otoliths. The number growth rate of0.225 mm/day (Fig. 6). The regression of increments observed after the tetracycline mark equation CAge = 3,433(SL) + 8.270, ,.2=0.93) was used regressed against the number ofdays since marking to backcalculate hatching dates from length frequen showed a 1:1 correspondence (Fig. 5). Ay-intercept cies. This age-length relation was also applied to 1989 value of zero was assigned to the regression. The collections for back-calculation purposes. Rotunno and Cowen: Temporal and spatial spawning patterns of Peprilus triacanthus 791
0.8 , 1988 ~. n=3.372 0.6 •• ..... 0.4 •..••"••
~ 0.2 fi, c .l!! 12 A III 1! 0.0 III 'liS g 0.8 .c 1989 15. Gl 'C n = 1.245 >- 'C • .B 0.6 • H• ea. .. 0.4
0.2
B
o 10 20 30 40 50 60
Standard length (mm)
Figure 4 Body depth to standard length versus standard length for Peprilus triacanthus collected during the spring and summer of1988 and 1989. Frame- and Thcker-trawl collections were combined.
Hatching for P. triacanthus in our samples occurs Fish caught in 1989 had a similar spawning pat from February through at least July and appears to tern to that of fish collected in 1988; the earliest be concentrated in two peaks that occur during early hatching date calculated was 14 February 1989, the spring and summer (Fig. 7, A and B). The earliest latest was 29 July 1989 (Fig. 7B). Spawning peaks hatching date recorded for fish caught in 1988 was occurred in late March to earlyApril in the SAB and 19 January 1988 and the latest was 22 July 1988. early to mid-June in the MAB. There appears to be a The winter-spring spawning appears to begin in reduction in spawning duringthe month ofMay along January and continue through late April, with an the U.S. Atlantic coast. apparent peak in March in the SAB (Fig. 7A). A de crease in spawningoccurs atthis time, although some spawningcontinues at a low level through May (Fig. Discussion 7A). Spring-summer spawning occurs during June and July in the MAB with a peak in late June. The Peprilus triacanthus is the most common species of relative strength ofthese two spawnings is not clear Peprilus found along theAtlantic coast ofthe United because sampling effort was not equivalent during States. Within the New York Bight, spawning and each season. larval presence for P. triacanthus is reported to oc- 792 Fishery Bulletin 95(4), J997
(2) 20 ;= 0.921(0) " = 0.989 2" n= 18 S .I!l r:::: 16 Ql E l!? () 12 .5 .(2) '0 (j; .c 8 2)" E ::;, z •.( (2). 4 (
0 0 4 8 12 16 20
Number of days since marking (D) Figure 5 Number of increments observed after oxytetracycline hydro chloride mark versus the number ofdays since marking for a subsample of1988 Frame-caughtPeprilus triacanthus. Num bers in parentheses represent the number offish. *n =3, but one otolith was not readable.
Table 2 Body depth-standard length ratios reported by Horn (1970). Ditty and Truesdale (1983). and from our Frame and Tucker trawl surveys.
Body depth-standard Standard length length range range (mm) n
Horn (1970") P. burti 0.460-0.640 7.80-167.00 232 P. triacanthus 0.364-0.600 10.60-198.00 202 P. alepidotus 0.565-0.877 18.22-222.00 205
Ditty (1981) P. burti 0.241-0.579 2.16-19.82 160 P. triacanthus 0.235-0.546 2.04-20.86 159 P. alepidotus 0.205-0.750 1.85-18.92 80
1988 and 1989 Frame and Tucker Spring 0.187-0.750 2.01-43.00 496 Summer 0.119-0.727 1.29-50.00 4.121 Spring and Summer 0.119-0.750 1.29-50.00 4,617
cur during summer only (Wilk et aI., 1990), Fahay 1) a species other than the most commonly found P. (1975) suggested however, on the basis ofthe range triacanthus spawns within theAtlantic (e.g. P. burti) of larval lengths collected in 1967-68, that spawn or 2) P. triacanthus or P. alepidotus has a more pro ing ofP. triacanthus may occur throughout the year tracted spawning season than previously thought. in the SAB. The occurrence oflarval and pelagic ju Peprilus larvae andjuveniles in our samples proved venile Peprilus within our spring samples collected to be P. triacanthus; therefore, our results demon in the northern SAB suggests two possible scenarios: strate an extended spawningperiodfor P. triacanthus Rotunno and Cowen: Temporal and spatial spawning patterns of Peprilus triacanthus 793
30 SL = 1.72 + 0.225(Age) .. 25 " = 0.9 n=60 ••• • • E • .§. 20 r· ..c: J• C. c:: .J!! 15 "E • as "C ~". c:: 10 enas _..,.fI 5
0 0 20 40 60 80 100 120
Number of increments (age in days)
Figure 6 Standard length versus the number ofincrements for a sub sample of 1988 Frame-caught Peprilus triacanthus.
Table 3 Vertebral counts for Peprilus collected by Collette (1963). Horn (19701, Ditty <1981>, and in this study (Frame).
Standard length (mm) range 16 17 17-18 18 18-19 19 20 n
Collette (1963) P. burfi 2 92 0 2 0 0 0 96 P. triacanthus 0 4 0 36 0 138 2 180
Horn (19701 P. burti 6.0-115.0 5 262 0 6 0 0 0 273 P. triacanfhus 6.0-115.0 0 7 0 62 0 208 2 279 P. alepidotus 6.0-115.0 3 176 0 3 0 0 0 182
Ditty (1981) P. burti 7.14-14.45 0 13 9 0 0 0 0 22 P. triacanthus 7.14-14.73 0 0 0 1 8 10 0 19 P. alepidofus 7.74-11.01 0 5 0 0 0 0 0 5
Frame Spring 1988 8.0-26.0 0 0 0 4 0 48 0 52 Summer 1988 8.0-26.0 0 1 0 6 0 39 0 46 Spring 1989 8.52-37.5 0 0 0 2 0 28 0 30 Summer 1989 8.0-38.0 0 0 0 6 0 39 1 46
'Ibtal Frame 8.0-38.0 0 1 0 18 0 154 1 174
in the Atlantic. According to back-calculated hatch differences in body depth need to be further analyzed ing dates, P. triacanthus spawns from late January before discounting the existence ofeither a polymor through at least July. We did not observe any sea phic P. triacanthus or a hybrid ofP. triacanthus and sonal differences in body depth. However, geographic P. burti. 794 Fishery Bulletin 95(4), 1997
200 "T-"------, 1988 A _ Spring-collected c=J Surrvner- 100 50 ~ 01131/88 02128188 03127188 04124/88 05122/88 06/19/88 07/17188 E ::::l Z 200 -.-- . --, 1989 8 _ Spring-collected c=J Summer-<:ollecled 150 n=391 100 50 01131/89 02128189 03128189 04/25189 05123189 06/26/89 07124189 Hatching date Figure 7 Back-calculated birthdate distributions for all spring and summer samples collected during 1988 and 1989. Frame- and Tucker-trawl samples were combined. Species identification ond, our other analyses (caudal vertebrae and mel anophore counts) supported the contention that P. According to the reported ranges ofbody depth-stan triacanthus was the dominant species ofPeprilus in dardlength ratios (Horn, 1970; Ditty and Truesdale, our samples. Our sample was predominantly com 1983), our larval specimens could have been anyone posed ofindividuals with 19 caudal vertebrae, which oftheAtlantic or Gulfcoast species ofPeprilus. How was consistent with findings ofprevious authors for ever, two points must be considered when interpret P. triacanthus (Collette, 1963; Horn, 1970; Ditty and ing these data. First, we found a strong allometric Truesdale, 1983). The ventral midline melanophore relation between body depth and standard length for counts were also similar to those used for P. triacan individuals smaller than 15 mm SL. Because the col thus by Ditty (1981). lections of Horn (1970) include fish ranging in size The overall results of the above morphometric, from 6 to 222 mm SL, this allometric relation could meristic, and pigment analyses lead us to conclude have confounded his conclusions. Dittyand Truesdale thatP. triacanthus is the dominant and probably the (1983), however, apparently recognized this problem only species ofPeprilus collected in our samples. The and therefore presented their data by size class. Sec- two most definitive characters for identification were Rotunno and Cowen: Temporal and spatial spawning patterns of Peprilus triacanthus 795 the number ofcaudal vertebrae and ventral midline rates, which are higher than our estimate for larvae melanophores. and juveniles and, therefore; would have underesti mated the spawning duration. Age and growth A bimodal hatching-date distribution in P. tria canthus is similar to that reported for another north Ages oflarval and juvenile P. triacanthus can be de south migrating species within the western Atlan termined by counting otolith increments. Validation tic, the bluefish, Pomatomus saltatrix (Kendall and was necessary because ofthe prevalence ofsubdaily Walford, 1979; Nyman and Conover, 1988). However, increments in this species. Secondary nuclei Hare and Cowen (1993) and Smith et al. (1994) have (multinucleation) were also noted inPeprilus otoliths. proposed that P. saltatrix spawns continually dur The cause and timing of the formation ofsecondary ing its north-south migration and that the apparent nuclei are not presently understood (Campana and bimodal hatching date distribution may result from Neilson, 1985), although these secondary nuclei have advective processes acting on the larval distributions been demonstrated to form during metamorphosis and from sampling artifact. in bluefish (Hare and Cowen, 1994). Secondary nu The presence ofan apparent bimodal spawning in clei, in butterfish otoliths, do not seem to follow a P. triacanthus, with spring and summer peaks, may consistent pattern in the development ofthe fish; we be an artifact of our sampling. Because we did not found that two sagittal bones from one fish frequently sample from April to June in each year and because contained differing numbers ofsecondary nuclei. Al our sampling locations were spatially distinct be though secondary nuclei may form during metamor tween spring and summer, it is possible that we did phosis (Campana and Neilson, 1985; Hare and not collect larvae spawned during May and early Cowen, 1994), we found secondary nuclei in larvae June. However, we could have collected older fish in that were several millimeters smaller than the size our samples that were spawned early in June. Data at which metamorphosis occurs (16 mm). collected monthly by the National Marine Fisheries Larval and early juvenile P. triacanthus from 6.0 Services (NMFS) as part oftheir Monitoring,Assess to 28.0 mm SL grew at a rate of 0.227 mm/day. Al ment, and Prediction (MARMAP) surveys suggest though ages of young butterfish have not been re that larvae are indeed present from April to August corded previously, Colton and Honey (1963) gave sizes in the MAB, thus it is likely that spawning occurs of P. triacanthus from hatching to six days of age. continually (Fig. 8). Moreover, MARMAP data indi Based on their estimates, growth rates ranged from cate a northward progression of larvae from near 0.01 to 0.55 mm/day and decreased with the age of Cape Hatteras during March or April (or both) into the fish. Specimens ofyoung P. burti have been aged the entire MAB by mid-summer and until October. with modal length-frequency analysis; growth rates This spatio-temporal pattern is consistent with the ofP. burti ranged from 0.25 to 0.56 mm/day (Murphy possibility of spawning associated with a seasonal and Chittenden, 1990). Peprilus burti may be ex northward migration of adult P. triacanthus. Hom pected to have a higher growth rate than P. (1970) has speculated thatbutterfish movements are triacanthus owing to the fact that it spawns in highly influenced by temperature (and salinity to a warmer waters ofthe GulfofMexico. lesser degree). Temperature-related movements by Our analysis of hatching-date distributions dem butterfish (and bluefish) would correspond with the onstrated that P. triacanthus has a more extensive observed northward progressionofyoung larvaefrom spawning season than previously reported. Their the SAB in the spring into the MAB in the summer spawning effort seems to be focused into two cohorts in association with seasonal warming. The extent of (spring: February-March; and summer: June-July) north-south migration by P. triacanthus, however, although evidence is presented that suggests at least requires further study. some fish spawn during the interim period between Inconclusion, this study adds to ourcurrentknowl seasonal peaks (i.e. late April to early June). Kawa edge ofthe early life history and spawning seasonal hara2 speculated that P. triacanthus may begin ityofbutterfish, P. triacanthus. Ourfinding ofa more spawning inApril. Itshould be noted that Kawahara protracted spawning season and ofa seasonal differ (1977) based his spawning estimate on adult growth ence between spawning locations should be ofvalue in reassessing management plans for this species. Current management plans arebased on conclusions that P. triacanthus spawns during summer months 2 Kawahara, S. 1977. Age and growth of butterfish, Peprilus only. The apparent similarity of spawning periodic triacanthus (Peck). in ICNAF Subarea 5 and StatisticalArea 6. ICNAF Res. Doc. 77NIJ27. June 1977 Annual Meeting. Far Seas ityofbutterfish to that ofbluefish (Cowen etaI., 1993; Fishery Laboratory, Shimizu, Japan. Hare and Cowen, 1994, Smith et aI., 1994) suggests 796 Fishery Bulletin 95(4). 1997 .. 71 74 72 71 74 72 Pepri/us triacanthus Peprilus triacanthus Mart:h19n~ April 19n-87 Lirvi. I 10 .1 LlrYl1 I 10 .- Do d Em .1-I0 .1-I0 : .., ~. li Il-IOO 42 .:,;-.:.:.. ...-. ',':' 42 .,' ' .... '" ". .:.>.:./ ;.~: 40 ••• ..... 0" : ••: ••••:. ::.:...:. : •• - 40 40 40 ..' '. .. ~:...... , " :' .',. ", .. :.. /'" '.' ••J' ...... :::;,.:/-.. 38 38 ...: . ..;': . :.;: .. ' 0; 31 31 74 70 68 61 74 70 18 66 .. 71 74 72 76 74 72 68 . Peprilus triacanthus Peprilus triacanthus May 19n-87 JLI1819n-87 brvil I 10 .1 llrvI, I 10 .1 0 .1-I0 "" ':..: .... :..•.•: -fS'!- .I~IO ~. 11-100 . . · ' ; Ii ...... Il-IOO , ...• :.: ":'" '.. 42 42 42 101-1000 ::-.:-,.~ 42 ...,.: i ..,..; .. ..>...... ,., ...,: ....' ",.::;}~~~;;c(J 40 ...... 40 40 ...... t :IID.lte;~ 38 38 36 36 74 72 70 68 61 74 72 70 68 66 Figure 8 MARMAP monthly averaged collections that a possible adaptive strategy may be shared by Acknowledgments these two seasonally migrating pelagic species. Per haps with closer inspection, other seasonally migrat We would like to thank all the people who assisted ing species may be found that share this spawning duringthe cruises and in the laboratory. In addition, strategy (Hare and Cowen, 1996). Further studyinto comments on earlier drafts were provided by Jeff the basis ofthis pattern is warranted. Buckel, Dave Conover, Steve Morgan, Michael Murphy, Rotunno and Cowen: Temporal and spatial spawning patterns of Peprilus triacanthus 797 71 74 72 .. 76 74 72 Peprilus triacanthus Peprilus triacanthus July 1977-87 Au!JJsl1977-87 .V L.rvle I 10 III llrYI! I 10 1111 0 il~\go <" ,1-10 EB ",rr.' 11-100 '!1-' • 101-1000 .. 42 42 42 1101-1000 40 40 40 N. i kllolleters I!!!IiiI!!IiiI o 100 38 38 36 36 74 72 70 68 66 74 72 70 68 II 71 74 72 44 76 74 72 Peprilus triacanthus .. Peprilus triacanthus 5eptember 1977-87 OCtober 1977-87 LIrYI! I 10 .z Larvae I 10 liZ d ,.",; .1-10 .I~IO ...... ~. R li 11-100 l1li 11-100 42 .." ••...... •... ',. 42 42 40 40 40 N i kllolleters I!!!IiiI!!IiiI o 100 38 38 31 38 74 72 70 II 74 72 70 18 II Figure 8 (continued) andtwo anonymous reviewers. JonHare provided help Literature cited withall phases oflarvalidentification andotolith analy sis. Mike Fahay generously provided Figure 8. This work is a result of research sponsored by the NOAA Brothers, E. B. 1980. Methodological approaches to the examination of Office of Sea Grant, U.S. Department of Commerce, otoliths in aging studies. In R. C. Summerfelt and G. E. under Grants #NA86AA-D-SG045 and #NA90AA-D Hallleds. I, Age and growth offish, p. 319-330. 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