Reproductive Biology of Southwestern Atlantic Wreckfish, Polyprion

Reproductive biology of southwestern Atlantic wreckﬁsh, Polyprion americanus (Teleostei: Polyprionidae)

Monicaˆ B. Peresa & Sandro Klippelb aServic¸o da Regiao˜ Litoral, DQA, FEPAM Rua Carlos Chagas 55 sala 707, Centro Porto Alegre, RS 90.030-020, Brazil (e-mail: [email protected]) bTalha-mar Projetos Ambientais, Cons. d’Avila 190 Porto Alegre, RS 91040-450, Brazil

Received 5 February 2003 Accepted 12 July 2003

Key words: sexual maturity, fecundity, spawning aggregation, spawning season, migration, deep-sea ﬁsh, life-cycle closure, southern Brazil

Synopsis

We report on the reproductive biology of southwestern Atlantic wreckfish. Females mature first at 77.9 cm total length (TL) (10.4 years) and all are mature by 90 cm TL (15.2 years). Males mature first at 74.9 cm (9 years) and all are mature by 80 cm TL (10.9 years). The wreckfish is a gonochoristic multiple spawner and the gonadal cycle is synchronized at the population level. Spawning occurs from late July to early October along the continental slope (>300 m). Ovarian fecundity varies from 3 to 11.9 million (135–311 oocytes × g−1) and increases exponentially with length. Spawning at western boundary current systems, maintained by homing of adults, is a basic requirement for self-sustaining populations of this species.

Introduction are mature and juveniles may live more than 2 years at the sea surface before recruitment to the bottom The wreckfish, Polyprion americanus (Bloch and (Sedberry et al. 1999). Despite its worldwide distri- Schneider, 1801), is a large, long-lived demersal teleost bution and high commercial importance, there is no that inhabits continental and oceanic island slopes of information on reproductive cycle, fecundity, spawn- temperate and subtropical waters of the northern and ing sites and season of these fish. The development southern Atlantic Ocean, Mediterranean, and south- of a method to sample whole fish from commercial ern Indian and southwestern Pacific Ocean (Heemstra landings permitted us to determine: (1) size and age at 1986, Sedberry et al. 1999). Along the southwestern maturity; (2) reproductive cycle; (3) spawning season Atlantic the species occurs from 23◦S, near Rio de and sites; (4) ovarian fecundity (OF); (5) sex ratio. Janeiro – Brazil, to 46◦S in Argentina (Cousseau & Perrota 1998, Peres 2000). The only published study on reproduction (Roberts Materials and methods 1989), reports southwestern Pacific wreckfish as a gonochoristic teleost. In New Zealand bottom trawl The study area was the continental shelf and slope off samples, females attained larger body sizes than males southern Brazil, from 27◦56’S to 34◦49’S (70–590 m and sex ratios were close to 1 : 1. Other related deep). It was divided in two sub-areas, north and south information is that wreckfish eggs and larvae are of Rio Grande (32◦13’S) (Figure 1). Southwestern pelagic (Hardy 1978) and that for southwestern Pacific, Atlantic wreckfish is landed and marketed ice-cooled both Polyprion species undergo a northern spawning and whole, at large body sizes and high prices. Thus, migration (Roberts 1996, Beentjes & Francis 1999). sampling procedures for commercial landings required For North Atlantic stocks, 8–12-year-old wreckfish fast and non-damaging techniques. Fish were measured 164

Figure 1. Study area of wreckfish, P. americanus, divided into two sub-areas off southern Brazil, (N) north and (S) south of Rio Grande. Area of capture of 27 females with hydrated oocytes (grayish) and of eight other, at five fishing sites (full circles), is shown. from the posterior border of the eye orbit to the fork of removed with a surgical curette through the urogeni- the caudal fin (EF in cm) with a flexible metallic tape tal pore (0.1–0.3 ml). This was sufficient to assign sex to the nearest cm. EF was converted to total length (TL and to provide qualitative information of the macro- in cm) by the relationship, TL = 119.5 × EF − 0.0724 scopic aspect of ovarian tissue, registered at dockside. (n = 125; r2 = 0.997; 44–192 cm TL). Sample weights Whenever possible, we preserved an ovary sub-sample were estimated with the total weight–TL relationship (0.5–2 ml) in 2% formalin to assess the frequency dis- TW (kg) = 6.29 × 10−6 × TL3.21 (n = 207; 44–174 cm tribution of oocyte diameters (OD) and their general TL; r2 = 0.98). microscopic aspect (16×). Sub-sampling of immature We determined sex for 641 randomly chosen indi- fish was not possible as gonads are small and tis- viduals, 420 females (74–174 cm TL) and 221 males sues are tightly compacted (n = 82). We removed (73–126 cm TL), by visual examination of sub-samples the left otolith through the opercular opening (420 of the posterior end of the gonads. Sub-samples were females, 221 males and 82 unsexed) and estimated 165 age by opaque band counts of transverse otolith sec- oocytes (YO, 0.6 < OD < 1.4 mm), referred here as tions (Peres 2000). Ice-preserved whole gonads and female OF, for 73 females without hydrated oocytes, lengths of other 114 females (45–174 cm TL) and 86 using the gravimetric method. All YO in a sample of males (44–119 cm TL) were provided by fishers. Addi- 0.2–0.4 g of ovarian tissue, preserved in 10% formalin, tional gonads of 67 females (46–148 cm TL) and 71 were separated from the interstitial tissue, counted and males (44–108 cm TL) were furnished from research extrapolated for preserved whole ovary weight using cruises. Weused exact binomial tests to determine if sex the relationship, OF = n◦YO × (GW/sample weight). ratios differed from the expected 1 : 1. We computed We estimated relative ovary fecundity (ROF) using the ◦ −1 Spearman’s rho coefficient (rs) to determine the corre- relationship: ROF (n YO × g ) = OF/EW. We con- lation between OF and TL. We performed all statistical sidered the presence of hydrated oocytes as evidence analyses in ‘R’ environment (Ihaka & Gentleman of spawning within a few hours (Hunter & Macewicz 1996). 1985) and used this to determine spawning season and Wreckfish gonads may weight up to 4 or 5 kg and spawning sites. We classified adult males by macro- we sampled most of them from commercial catches, scopic visual aspect of the non-preserved testes or after being ice-cooled for 10–25 days. Thus, histolog- by the presence of sperm in gonad sub-sample. We ical sections were of poor quality and were only used classified females by: (1) macroscopic visual aspect to confirm the criteria for gonad staging. We did not of the non-preserved ovarian and oocytes; (2) micro- quantify the atresia rate but its seemed negligible. We scopic general aspect of preserved whole oocytes and, could determine gonad staging in a five-point scale for (3) the microscopic aspect of the histological sections, 462 females (410 adults) (Table 1). Gonad staging for when available. We calculated length at first maturity male wreckfish sub-samples was not possible during (Lm = 50% maturity) by PROBIT regression of adult commercial landings and so we did not assess it in proportion for each length class (5 cm class intervals) this study. We separated ovarian follicles, here called during the active reproductive period. We obtained oocytes, with diameters greater than 0.05 mm, aligned ages at first maturity from the relationship, Age = t0– and measured in a random axis (16×) for 314 female (1/K) × ln (1−(Lm/L∞)), where t0, K and L∞ are the wreckfish (291 adults). For 181 females and 157 males, von Bertalanffy growth model parameters obtained for we used fresh gonad weight (GW in kg) to calculate the females (−6.80 years, 0.054 years−1 and 129.5 cm) gonad-somatic index, GSI = (GW/EW) ×100, where and males (−4.69 years, 0.084 years−1 and 109.5 cm) EW (kg) is the eviscerated somatic weight, estimated wreckfish (Peres 2000). All observed females greater by the relationship EW = 9 × 10−6 × TL3.12 (n = 141; than 90 cm TL were clearly mature. As mature rest- r2 = 0.98). We estimated the total number of yolked ing and immature females are difficult to distinguish,

Table 1. Monthly sample sizes and body length ranges (TL in cm) of wreckﬁsh P.americanus, assessed for gonadal stages (GSt), gonad-somatic index (GSI), oocyte diameter distribution (OD) and ovarian fecundity (OF). In the parenthesis is the number of adult ﬁshes examined.

Month Female Male GSt GSI OD OF TL GSI TL

Jan. 14 (14) — 14 (14) — 91–130 — — Mar. 16 (16) 2 16 (16) — 90–155 3 77–91 Apr. 49 (38) 31 48 (38) 20 55–137 51 58–108 May. 63 (60) 63 59 (58) 27 71–148 26 88–109 Jun. 34 (31) 4 33 (31) 1 79–137 2 73–78 Jul. 105 (100) 22 47 (46) 14 46–137 16 57–112 Aug. 16 (6) 16 11 (6) 6 47–174 35 48–105 Sept. 105 (90) 37 53 (49) 5 48–140 19 56–100 Oct. 37 (36) 2 17 (17) — 87–134 2 72–73 Nov. 4 (0) 4 — — 47–49 2 44–47 Dec. 19 (19) 0 16 (16) — 92–122 1 103 TL 46–174 46–174 55–174 74–174 46–174 44–112 Total 462 (410) 181 314 (291) 73 157 166 monthly GSI analysis included all females greater than pore. OD frequency distribution for each ovarian stage 90 cm TL as adults. shows the sequence of ovary development (Figure 2). Oocyte color, aspect and diameter change with development (Table 2). Description of immature, resting, Results early and late development, running-ripe and spent ovaries are given in Table 3. In seven partially spawned Gonad structure and development whole ovaries (Sep.–Oct.), most oocytes were in late yolked stage and gonads were flaccid with hemorrhagic Wreckfish ovary and testis organization follow the portions. general patterns for a gonochoristic teleost species. The presence of partially spawned females, OD dis- Both are paired organs, joined posteriorly and con- tributions of running-ripe females with three modal nected medially to the coelom wall by a mesentery. groups (immature, yolked and ripe oocytes) and sev- Ovaries have circular sections, radial lamellar orga- eral oocyte stages in the same histological section, are nization, a central lumen and a blood vessel network evidence that the species is a multiple spawner. around the external wall. Testes are compact with a triangular section, tubular organization, and a dorsal invagination with a central vascular bundle and the Reproductive cycle spermatic duct. In the ovary, oocytes are produced and ripened within the lamellae, ovulated in batches into the With gamete and gonad development, GSI monthly lumen, and released externally through the urogenital mean values of adult fish increased from March to July,

Figure 2. OD distribution for each ovary stage (n = 100) of wreckfish, P. americanus. 167 reaching 8.8 for females and 5.5 for males (Figure 3). females were common from September to January A gradual decline of GSI and higher SE from July and almost absent from March to August. Despite to September are evidence that these are the spawn- gathering data over several years, the monthly OD ing months when successive ripening and liberation distribution of pooled adult female weighed by the of gametes are responsible for the high variability number of measured oocytes showed that the reproduc- and overall decrease in GW. Monthly relative fre- tive cycle is quite synchronized at the population level quency of adult female GSt confirmed the timing of (Figure 5). gonad development and spawning, obtained from the The gradual increase of yolked OD throughout the GSI data (Figure 4). Early development was frequent active reproductive period (Figure 6), and OD monthly from March to June and late development from July distributions with no more than three modes and a to August. We observed running-ripe females in late gap of OD between non-yolked and YO from June July, September and early October. Spent and resting on (Figure 5), are evidence that prior to the spawning months (late July–early October) there is no more recruitment of immature oocytes and that wreckfish OF Table 2. Oocyte stages of wreckfish, P.americanus. Color, diameters (OD) and general microscopic aspect (16× magnification). is determinate (Hunter et al. 1992, Gunderson 1993).

Immature oocytes transparent, colorless, inconspicuous to the naked eye (OD 0.15–0.2 mm). Whole oocytes are difficult to Ovarian fecundity separate, a thin oocyte wrapper maybe visible Early YO opaque-whitish to yellow (OD 0.3–0.7 mm), have a Relative ovarian fecundity increased from April to July, granular cytoplasm (30–80% of oocyte volume) with two to indicating that YO are not totally recruited, at least by three halos and a well-defined wrapper April and May (Figure 7). Decreasing relative fecun- Late YO bright yellow to coral-orange (OD 0.6–1.4 mm), dity from July to September is additional evidence that compact yolk layers and a distinct wrapper. Whole oocytes these are the spawning months. The number of late YO are easy to separate increased with female body length (Figure 8). For 11 Ripe or hydrated oocytes in ovulating females are large females caught from 1 June to 15 July, when fecundity (OD 1.5–2.2 mm), uniform-hyaline, whitish after is already determined and spawning was not observed, preservation, with one to three oil droplets and a thick, OF varied from 3 million oocytes (116 cm TL) to 11.9 well-developed wrapper million (137 cm TL) and was significantly correlated

Table 3. Ovarian stages of wreckﬁsh, P.americanus. Criteria included: (1) the macroscopic visual aspect of non-preserved ovaries; (2) general microscopic aspect of ovarian tissue and oocyte stages present (descriptions in Table 2); (3) GSI range.

Immature ovaries (1) are cylindrical, filiform, compact, pink, translucent, with no visible oocytes. (2) Compact tissue, no spacing between ovarian lamellae, 100% immature oocytes. Thin ovarian capsules. (3) GSI 0.5 Resting ovaries (1) are rounded, opaque-pink, oocytes difficult to see with naked eyes, developing peripheral blood vessel networks. (2) Compact tissue. Immature and very early YO are present. Ovarian capsule thicker than immature. (3) GSI 0.5–1.5 Early developed ovaries (1) are swollen, yellow–orange, with marked peripheral blood vessel networks, oocytes visible to the naked eye. (2) Immature and early YO, developing radial septa from a thickening ovarian capsule. (3) GSI 1–5 Late developed ovaries (1) are enlarged and brittle, difficult to handle due to extended ovarian walls, easily visible oocytes. Developed peripheral blood vessel networks with or without hemorrhagic portions. (2) Late YO comprised 80–95% of sample volume and the rest, immature oocytes. Some ripe oocytes from earlier batches may be present. (3) GSI 4–15 Running ripe ovaries (1) are very enlarged, part or totally transparent due to ripe oocytes that are easily released. Ovarian capsules are distended to the maximum. There are highly developed peripheral blood vessel networks. (2) Ripe oocytes comprised 40–100% of sample volume; late YO may still be present. (3) GSI 9–18 Spent ovaries (1) are small, emptied, reddish, totally or partly hemorrhagic, visible oocytes may be present. (2) Thickened ovarian walls and septa. Spaced ovarian lamellae with hanging tissue like ‘grape bunches’. Immature and very early YO are present. Some ovaries contained transparent structures similar to ‘empty wrappers’ (supposed to be postovulatory follicles) and/or remaining ripe oocytes of earlier batches. (3) GSI 2–3 168

Figure 3. Monthly mean (full circles) and standard error (bars) of GSI (as a percent of eviscerated weight) of wreckﬁsh, P. americanus. (A) Adult females (n = 133) and (B) adult males (n = 87).

with body length (rs = 0.77; p = 0.008). This relationship is best ﬁt by the potential function (SEpotential = −6 −6 1.87 × 10 smaller than SElinear = 1.90 × 10 ).

Sexual development

In the reproductive active months (Apr.–Sep.), female GSI and OD increased with body size. For females smaller than 74 cm TL, GSI was up to 2 (Figure 9A) and maximum OD, up to 0.2 mm (Figure 10). All females greater than 90 cm TL had GSI from 2 to 18 and maximum diameters of YO between 0.5 and 1.4 mm. Female sexual maturation occurred from 74 to 90 cm TL, 8.9–15.2 years old, and length and age at first maturity were 77.9 cm TL and 10.4 years old, respectively (Figure 11A). From April to September, testes of males up to 70 cm Figure 4. Monthly relative frequency of ovary stages of adult TL were clearly non-reproductive and GSI were less wreckfish P. americanus. See Table 1 for sample sizes. than 1. All male wreckfish over 80 cm TL had GSI 169

Figure 5. Monthly OD distribution (mm) of pooled adult female of wreckﬁsh, P. americanus weighed by number of measured oocytes per ﬁsh. Monthly number of females in parentheses.

Figure 6. Mean diameter (mm) of YO per female (n = 141) by month, of wreckfish, P. americanus. 170 from 1 to 14 and were adult (Figure 9B). Male sexual Spawning maturation occurred from 70 to 80 cm TL, 7.4 to 10.9 years old, and length and age at first maturity were We caught a total of 22 running-ripe females and 13 74.9 cm TL and 9 years old (Figure 11B). others with remaining hydrated oocytes in their ovaries along the continental slope, in water depths of 300– 500 m (Figure 1). Most of them (n = 34, 97%) were captured north of Rio Grande and 77% (n = 27) were sampled from three huge commercial catches: 29 July 1995 (13 t of wreckfish), 9 September 1995 (26.6 t) and 4 October 1995 (16.4 t), at a fishing area known as ‘Tramanda´ı-Solidao’˜ (30◦05S, 048◦W–30◦45S, 048◦30W, 360–460 m deep). We recorded males (n = 30) with distended testicles (GSI > 5) and sperm being spontaneously released at these same catches. The relative number of running-ripe females at these three landings increased from 2% in July (one out of 53 sampled adult females), to 10% in September (six of 60) and to 36% in October (13 of 36). Late development stage frequency was high in July (98%) and dropped in the following two landings (18% in Sep., 17% in Oct.). Spent females were completely absent in July, were 72% in September and 47% in October. Of 179 sampled adult wreckfish, 149 (83%) were female. The sex ratio was significant different from 1 : 1 (p 0.001). Figure 7. Monthly ROF of wreckfish, P. americanus. ROF as the Wreckfish spawning occurs at the continental slope number of late YO (0.6–1.4 mm) per gram of eviscerated body (300–500 m deep) off southern Brazil, especially at weight. Median and interquartile ranges (boxes), minimum and maximum values (dashed lines) and outliers, values outside 1.5 Tramanda´ı-Solidao˜ fishing area. Commercial catches times of the first and third quartile (empty circles). See Table 1 at spawning sites and season were highly female biased for sample sizes. (p 0.001).

Figure 8. Relationship of (OF ×10−6) and body TL (in cm) of wreckﬁsh, P. americanus. OF as the number of late YO (0.6–1.4 mm). Crosses for April and May samples (n = 47), open circles for 15 July to September (n = 15) and full circles for 1 June to 15 July (n = 11). Equation, SE and df of the relationship (line) for 1 June to 15 July samples are shown. 171

Figure 11. Proportion of adult fish per total length classes (full circles) and PROBIT regression (lines). Estimated values of length at 50% maturity are indicated for (A) female (n = 110) Figure 9. Relationship of GSI (as a percent of eviscerated weight) = and body TL (cm) of wreckfish P. americanus in reproductive and (B) male (n 118) wreckfish, P. americanus. active months (Apr.–Sep.). (A) Female, full circles for GSI values up to 2. (B) Male, full circles for GSI values up to 1. See Table 2 similar to that described by Roberts (1989) for south- for sample sizes. western Pacific stocks. In the study area, wreckfish is a multiple spawning, gonochoristic teleost species. The gonad cycle is annual and quite synchronized at the population level, with reproductive rest from late spring to summer, gonad development from autumn to early winter, and spawning season from late July to early October. Gonad sub-sampling of immature fish was not possible and immaturity was assessed only when whole gonads were available. Thus, the observed size and age at first maturity are surely underestimated. How- ever our estimated values are not very different from those reported by Sedberry et al. (1999) where most 8–12-year-old wreckfish harvested in the U.S.A. are mature. Wreckfish maximum values of monthly mean GSI were high for both males and females. Data tab- Figure 10. Relationship of maximum oocyte diameter (mm) mea- ulated for eight reef fish species (Sadovy 1996) show sured per fish and body total length (cm) of wreckfish, P. ameri- that only Acanthopagrus cuvieri females have monthly canus = in reproductive active months (Apr.–Sep.) (n 199). Full > circles for maximum oocyte diameters up to 0.5 mm (n = 15). GSI larger than wreckfish ( 20). Wreckfish aggregate to spawn in deep waters (>300 m) off southern Brazil, especially north of Rio Discussion Grande, though it is possible that some fish spawn in pairs or small groups along the entire continental slope. The observed gonad gross and micro structure for male Large-sized testes (male GSI up to 14) are an addi- and female wreckfish of southwestern Atlantic was tional indication that the species is a group spawner 172

(Sadovy 1996). There is evidence that adult fish inhab- juvenile stages, the wreckfish recruits to the bottom iting the southern fishing area perform a northward in shallower waters of the continental shelf, from spawning migration but there is no data of how long this southern Argentina (35–45 cm TL) (Nakamura 1986) might be (Peres 2000). A northward migration of about to southern Brazil (44 cm TL, 1.5 years old) (Peres 700 km before spawning, in late winter, was observed 2000). Large, mature fish have not been described for for New Zealand wreckfish (Roberts 1996, Roberts1). Argentine or Uruguayan waters (Cousseau & Perrota Beentjes & Francis (1999), from tag and recapture data, 1998, Peres 2000) but they spawn in the continental reported a northward seasonal migration up to 1 389 km slope of southern Brazil. Spawning in warm waters for New Zealand hapuku P. oxygeneios. The straight enables wreckfish egg and larvae to develop, even dur- line distance between the extreme limits of our study ing winter–spring months, while they are passively area is about 480 nautical miles (890 km) and the dis- transported southwards. tance between areas of higher fishing yields (Valao˜ The SASG does not seem to be the oceanographic and Tramanda´ı-Solidao)˜ is about 300 nautical miles feature responsible for life-cycle closure of southwest- (550 km). It would be reasonable to assume a seasonal ern Atlantic wreckfish, because of its larger extent, migration, back and forth, of up to 1 000 or 1 500 km. compared with the NASG. The absence of a well- The North Atlantic wreckfish has a complex life his- develop fishery in the eastern Atlantic coast (Sedberry tory. The adult demersal phase spawns in deep waters et al. 1999) agrees with this. The northward recircula- of North American coast (Blake Plateau, 32◦N, 79◦W). tion cell of the Brazil current front (Campos et al. 1995) The extended pelagic juvenile interval (up to 50 cm could be the physical feature responsible for retention TL and 2 years) drifts in the North Atlantic gyre and of larvae and juveniles in the region. Vagrancy (sensu descends to the bottom in the eastern North Atlantic Sinclair 1988) through the south Atlantic current could (Sedberry et al. 1999). Because oceans are diffusive explain the occurrence of wreckfish in the southeast- and advective environments, a specific oceanographic ern Atlantic and maybe, in all other places of the world pattern of spawning location that gives a chance of without self-sustained populations. life-cycle closure is an important requirement for All wreckfish life stages occur around southeast- self-sustaining populations with complex life histo- ern Australia and New Zealand. With its congeneric ries (Sinclair 1988, Sinclair & Iles 1989). The North species P. oxygeneios (‘hapuku’), wreckfish (‘bass’) Atlantic wreckfish spawning ground is under the influ- sustain an important recreational and commercial fish- ence of the Gulf Stream, a warm western boundary cur- ery (Paul 1995, Roberts 1996) indicating that this is a rent of the North Atlantic Subtropical Gyre (NASG). self-sustaining population of P. americanus too. Alike This would be the oceanographic feature that retains southern Brazil (30◦–31◦S) and southeastern U.S.A. and passively transports wreckfish early life stages. (32◦N), the southeastern Australia continental margin The time duration of this pelagic interval agrees with is under the influence of a western boundary system, this. As all life stages occur within the NASG, the the east Australia current. North Atlantic wreckfish is considered a self-sustained We argue that western boundary current systems population (sensu Sinclair 1988). are a basic requirement for self-sustaining wreck- The southern Brazil continental slope is domi- fish populations. This retention mechanism diminishes nated by the southward motion of the Brazil current, losses due to vagrancy. Homing of adults to spe- a warm (>20◦C) western boundary current of the cific spawning sites generates temporal persistence South Atlantic Subtropical Gyre (SASG) (Castro & of larval distribution in particular geographic space Miranda 1998). While weaker than the Gulf Stream and mate assemblage (Sinclair & Iles 1989). Thus, in terms of mass transport, the Brazil current is migration of wreckfish spawners to these systems is energetically comparable to its North Atlantic coun- the weak link in completing their life cycle. Long terpart, particularly in the southern part of the sub- migrations have been observed for all self-sustaining tropical gyre (Campos et al. 1995). The southwestern populations of wreckfish in the southwestern Atlantic, Atlantic wreckfish is also a self-sustained population north Atlantic (Sedberry et al. 1999) and southwest- of P. americanus. Although we did not observe pelagic ern Pacific (Roberts1). If this is true, southwestern Pacific wreckfish spawning grounds should be some- ◦ 1 Roberts, C. 2000. Museum of NZ Te Papa, 169 Tory Street, where between New Zealand and Australia (30 S), over PO Box 467. Wellington, New Zealand. pers. comm. continental or islands slopes north of the Tasman front. 173

Southwestern Atlantic wreckfish reproductive invest- Cousseau, M. & R. Perrota. 1998. Peces marinos de Argentina: ment is remarkably high. Besides the presence of a Biolog´ıa, distribucion,´ INIDEP, Mar del Plata, Argentina. long spawning migration and high fecundity, wreckfish 000 pp. eggs are quite large (OD 2 to 2.2 mm) when compared Gunderson, D. 1993. Surveys of Fisheries Resources, John Wiley & Sons, New York. 248 pp. with pelagic eggs of other teleosts (Hardy 1978). Since Hardy, J. 1978. Development of fishes of the Mid-Atlantic Bight. estimated natural mortality for the demersal–exploited An atlas of egg, larval and juvenile stages, Vol. III. Fish and interval (ages 6–9 years) is low, around 0.05–0.09 Wildlife Service, U.S. Department of the Interior. (Peres 2000), losses due to vagrancy during pelagic Heemstra, P. 1986. Family No. 165; Polyprionidae. In: stages would explain this reproductive investment. M. Smith & P. Heemstra (ed.) Smith’s Sea Fishes, 6th edn, Springer-Verlag, Berlin. Hunter, J. & B. Macewicz. 1985. Measurement of spawning fre- Acknowledgements quency in multiple spawning fishes. pp. 79–94. In: R. Lasker (ed.) An Egg Production Method for Estimating Biomass of Pelagic Fish: Application to the Northern anchovy Engraulis Part of these results was submitted in a Ph.D. thesis mordax. NOAA Technical Report 36, U.S. NMFS. of the Biological Oceanography Post-Graduation, Uni- Hunter, J., B. Macewicz, N. Chyan-Huel Lo & C. Kimbrel. versity of Rio Grande (FURG) – Brazil, and was 1992. Fecundity, spawning, and maturity of female Dover sole supported by grants from the Brazilian Ministry of Edu- Microstomus pacificus, with an evaluation of assumptions and cation (CAPES). Thanks to southern Brazilian skippers precision. Fishery Bulletin U.S. 90: 101–128. and fishers, specially Antonio Bianchi, for access to Ihaka, R. & R. Gentleman. 1996. A language for data analysis and graphics. J. Comput. Graph. Stat. 5: 299–314. their wreckfish catches, whole gonads and for pro- Nakamura, I. 1986. Important Fishes Trawled off Patagonia, viding catch and effort data for many years; to Lucio Japan Marine Fishery Resource Research Center, Tokyo. Waengertner Pires and George Kotas for field assis- 369 pp. tance; to Maria Paula Mellito da Silveira and Joao˜ Paul, L. 1995. Groper. Seafood New Zealand 3: 26–31. Carlos Cousin for histological assistance; to Manuel Peres, M.B. 2000. Dinamicaˆ populacional e pesca do cherne- Haimovici for whole wreckfish gonads from research poveiro Polyprion americanus (Bloch e Schneider, 1801) (Teleostei: Polyprionidae) no sul do Brasil. Ph.D. thesis, cruises. Many thanks to David Wyanski, Clive Roberts Fundaçao˜ Universidade Federal do Rio Grande, Rio Grande, and Dave Japp for unpublished information on wreck- Brazil. 151 pp. fish from U.S.A., New Zealand and South Africa. Roberts, C. 1989. Reproductive mode in the percomorph fish Thanks to Beatrice Padovanni Ferreira and Carolus genus Polyprion Oken. J. Fish Biol. 34: 1–9. Maria Voorenfor critical reviews that greatly improved Roberts, C. 1996. Hapuku and bass: The mystery of the missing earlier versions of this manuscript and George Sedberry juveniles. Seafood New Zealand 4: 17–21. Sadovy, Y. 1996. Reproduction of reef fishery species. pp. 15–59. for many fruitful discussions. In: N. Polunin & C. Roberts (ed.) Reef Fisheries, Chapman & Hall, London. Sedberry, G., C. Andrade, J. Carlin, R. Chapman, B. Luckhurst, References C. Manooch III, G. Menezes, B. Thomsen & G. Ulrich. 1999. Wreckfish Polyprion americanus in the North Atlantic: Fish- Beentjes, M. & M. Francis. 1999. Movement of hapuku eries, biology and management of a widely distributed and (Polyprion oxygeneios) determined from tagging studies. N. Z. long-lived fish. Am Fish. Soc. Symp. 23: 27–50. J. Mar. Freshw. Res. 33: 1–12. Shapiro, D. 1987. Reproduction in groupers. pp. 295–328. In: Campos, E., J. Miller, T. Muller¨ & R. Peterson. 1995. Physical J. Polovina & S. Ralston (ed.) Tropical Snappers and Groupers: oceanography of the southwest Atlantic Ocean. Oceanography Biology and Fisheries, Westview Press, London. 8: 87–91. Sinclair, M. 1988. Marine populations: An essay on population Castro, B.M. & L.B. Miranda. 1998. Physical oceanography of regulation and speciation. Washington Sea Grant/University of the Western Atlantic continental shelf located between 4N and Washington Press, Seattle. 34S. Coastal segment (4,W). pp. 209–251. In: A.R. Brink & Sinclair, M. & T.D. Iles. 1989. Population regulation and K.H. Robinson (eds) The Sea, Vol. 11, John Wiley & Sons, speciation in the oceans. J. Cons. int. Explor. Mer 45: New York. 165–175.