LIFE HISTORY OF PLESIONIKA EDWARDSI (CRUSTACEA, DECAPODA, PANDALIDAE) AROUND THE CANARY ISLANDS, EASTERN CENTRAL ATLANTIC

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1 S. Afr. J. mar. Sci. 18: LIFE HISTORY OF PLESIONIKA EDWARDSI (CRUSTACEA, DECAPODA, PANDALIDAE) AROUND THE CANARY ISLANDS, EASTERN CENTRAL ATLANTIC J. I. SANTANA*, J. A. GONZÁLEZ*, I. J. LOZANO ad V. M. TUSET* The life history of Plesioika edwardsi (Bradt, 1851) aroud the Caary Islads i the Easter Cetral Atlatic was ivestigated, based o a total of shrimps ragig i legth betwee 8 ad 40 mm carapace legth (CL). The species carries out seasoal migratios; they cocetrate i deep water durig witer, move shallower i summer ad retur to deep water agai i autum. Ovigerous females occur throughout the year, but a spawig peak was determied betwee April ad September. The size at maturity for females was approximately 26 mm CL. Shrimp size geerally icreased with icreasig water depth. The growth parameters for males were L = mm CL ad K = 0.55 year -1, ad L = mm CL ad K = year -1 for females. The species displays the typical reproductive patter of tropical padalids ad is dioecious. Plesioika edwardsi (Bradt, 1851) is a marie species of wide distributio at low latitudes. It is kow from the Wester Pacific (Philippies, Idoesia), the Wester Atlatic (from South Carolia ad North Bahamas to the Gulf of Mexico), the Easter Atlatic (from North-West Spai to Sierra Leoe, icludig the archipelagos of Azores, Madeira, Caaries ad Cape Verde ad most of the Mediterraea), ad the South-Wester Idia Ocea aroud the Seychelles (Crosier ad Forest 1973, Holthuis 1980, 1987, Chace 1985, Itès ad Bach 1989, Gozález et al. 1990, Frase 1991, Martis ad Hargreaves 1991, Biscoito 1993). Those authors have recorded the species at bottom depths of m o mostly muddy substrata, but also o sady or rocky bottoms over the cotietal shelf ad upper cotietal slope. P. edwardsi has bee icluded i the F. A. O. catalogue of species of iterest to fisheries (Holthuis 1980). Zariquiey Álvarez (1968) reported it as beig caught by trawlers off the Mediterraea coast of Spai. It is believed to be of some ecoomic iterest i Spai, Italy, Morocco, Algeria ad Tuisia, where it is sold i fish markets with other shrimps (Holthuis 1980, 1987). Sice 1984, P. edwardsi has bee caught i abudace with multiple shrimp traps o the steep grouds betwee 75 ad 500 m deep i the Wester Mediterraea (the east coast of Spai, Balearic Islads, Corsica, Sardiia ad Sicily). Durig the period , aual Spaish catches varied betwee 80 ad 100 tos (Gozález et al. 1992). Itès ad Bach (1989) reported the species to be of ecoomic iterest i the Seychelles. Despite its abudace ad widespread distributio, P. edwardsi has ot bee studied i much detail (e.g. Kig 1986, Itès ad Bach 1989, Martis ad Hargreaves 1991). The results of more tha 20 fishig surveys i the deep waters aroud the Caary Islads have suggested that P. edwardsi ad Heterocarpus esifer are occasioally abudat ad of possible, but restricted, ecoomic iterest (e.g. Sataella ad Bravo de Lagua 1975, Gozález et al. 1988, Caldetey et al. 1992, Gozález 1995). Off the Azores, a trial fishery usig bottom traps at depths ragig betwee 18 ad 864 m showed that the most commo ad abudat shrimp caught there was Plesioika arval, followed by P. edwardsi (Martis ad Hargreaves 1991). I the archipelago of Madeira, exploratio with bottom traps dow to m (et at depth) revealed that P. arval was the most abudat padalid shrimp, but large catches of P. edwardsi were take betwee 130 ad 360 m (Biscoito 1993). Aroud the Caary Islads, P. arval is the target species of a small artisaal fishery o the arrow shelves ad steep slopes of the wester ad cetral islads. Fishig is carried out with bottom shrimp traps set maily betwee 100 ad 150 m water depth. P. arval represets umerically ad by mass about 85% of the total shrimp catch, the remaiig percetage cosistig of P. edwardsi, H. esifer ad other sublittoral shrimps. Although fisheries statistics are ot available, up to 10 tos of padalid shrimps might be caught aually. This study provided iformatio o the basic biology ad biological parameters of P. edwardsi aroud the Caary Islads. The paper cotributes to the * Istituto Caario de Ciecias Marias, D.G. Uiversidades e Ivestigació, Gobiero de Caarias, P.O. Box 56, E Telde (Las Palmas), Spai. solea@iccm.rcaaria.es Departameto de Biología Aimal, Uiversidad de La Lagua, Astrofísico F. Sáchez s/, E La Lagua (Sata Cruz de Teerife), Spai Mauscript received: April 1996

2 40 South Africa Joural of Marie Sciece Table I: Cruise ad samplig iformatio of shrimps take betwee 1974 ad 1994 aroud the Caary Islads Cruise Date Islad Latitude ( N) Logitude ( W) Sample size Size rage Depth rage (m) (CL, mm) AGAMENÓN 7406 MOGÁN 8701 MOGÁN 8701 MOGÁN 8710 MOGÁN 8802 MOGÁN 8804 MOGÁN 8804 MOGÁN 8806 GOMERA 9009 CANARIAS 9206 CANARIAS 9206 TALIARTE 9403 BOCINEGRO 9412 Jue 1974 Jue 1985 Jue 1985 Jue 1985 Jue 1985 Jue 1985 Jue 1985 Jue 1985 July 1985 July 1985 Jauary 1987 February 1987 October 1987 February 1988 April 1988 May 1988 Jue 1988 Jauary 1990 February 1990 July 1990 August 1990 September 1990 September 1990 October 1990 November 1990 May 1992 Jue 1992 March 1994 December 1994 P CF L TG H P C FC C CC C CC T TT T TG T TT T CC Total P = La Palma, C = Gra Caaria, F = Fuertevetura, L = Lazarote, T = Teerife, G = La Gomera, H = El Hierro

3 1997 Sataa et al.: Life History of Plesioika edwardsi aroud Caary Islads 41 Fig. 1: Depth distributio of P. edwardsi off the Caary Islads, expressed i terms of cpue: total catches ad catches of ovigerous females preseted separately kowledge of the life history of this padalid species, ad may be of future importace should it become ecessary to assess ad maage the stock. MATERIAL AND METHODS About 12 research surveys were made to the Caary Islads i the Easter Cetral Atlatic be- Table II: Effort ad mass of total ad ovigerous shrimps caught per 50 m depth iterval Mass caught (g) Depth iterval Effort (umber (m) of traps) Total catch Ovigerous shrimps Total Fig. 2: Seasoal depth distributio of P. edwardsi off the Caary Islads. Data expressed i terms of cpue: total catches ad catches of ovigerous females preseted separately

4 42 South Africa Joural of Marie Sciece Fig. 3: Mothly frequecies of ovigerous females i the populatio of P. edwardsi off the Caary Islads twee N ad W durig the period (Table I). Durig these cruises, bottom traps were set o the isular shelf ad slope regios at depths ragig from 54 to 468 m depth (e.g. Sataella et al. 1975, Sataa et al. 1987, Gozález et al. 1988, Lozao et al. 1990a, b, 1992, Herádez et al. 1991, López Abellá et al. 1994, Fig. 5: Size frequecy distributios of (a) o-ovigerous ad ovigerous ad (b) male ad female P. edwardsi off the Caary Islads Fig. 4: Relatioship betwee frequecy of ovigerous females ad carapace legth of P. edwardsi off the Caary Islads Gozález 1995). A total of P. edwardsi was studied from these cruises, from which 75.6% were measured (size rage 8 40 mm carapace legth, Table I). P. edwardsi was ot targeted durig the research surveys, which formed part of a larger study o the etire padalid shrimp assemblage. Therefore, fishig effort across the bathymetric rage from 50 to 500 m was more or less equally distributed over each 100 m depth iterval. Differeces i the actual umber of traps set per 50 m depth iterval reflect variable weather coditios (Table II). Most of the specimes caught were separated with respect to their ovigerous or o-ovigerous coditio ad couted. The carapace legth (CL) of a subsample from each group was measured (± 0.1 mm) dorsally

5 1997 Sataa et al.: Life History of Plesioika edwardsi aroud Caary Islads 43 from the posterior edge of the eye socket to the posterior edge of the carapace usig a verier caliper. The total wet mass (W) of each shrimp was measured (± 0.1g), mostly from fresh material. The sex of oovigerous idividual samples (females, males ad sexually uidetified specimes) was determied after 1985, accordig to the presece/absece of the appedix masculia o the edopod of the secod Males Sex/Group Table III: Seasoality i mea size of shrimps per 50 m depth iterval Value per depth iterval (m) Seaso Jauary March Mea size (CL, mm) April Jue Mea size (CL, mm) July September Mea size (CL, mm) Females Jauary March Mea size (CL, mm) April Jue Mea size (CL, mm) No-ovigerous shrimps July September Mea size (CL, mm) October December Mea size (CL, mm) Jauary March Mea size (CL, mm) April Jue Mea size (CL, mm) July September Mea size (CL, mm) October December Mea size (CL, mm)

6 44 South Africa Joural of Marie Sciece Table III (cotiued) Sex/Group Ovigerous females Value per depth iterval (m) Seaso Jauary March Mea size (CL, mm) April Jue Mea size (CL, mm) July September Mea size (CL, mm) October December Mea size (CL, mm) pleopod (Kig ad Moffitt 1984). Shrimp abudace was estimated idirectly usig catch-per-uit-effort (cpue) data (i.e. mass of shrimp per trap). The seasoal distributio of shrimp size ad depth was ivestigated at 50 m depth itervals. The mass of shrimp per trap was calculated separately for ovigerous females ad total shrimp. Sexes were treated separately, ad samples cosistig of <40 idividuals were ot aalysed. The spawig seaso was determied from the mothly frequecy of ovigerous females. A sexual maturity curve was derived usig a logistic fuctio (Pope et al. 1983). The mea legth (CL) at maturity i females was calculated as the legth at which 25% of the populatio was ovigerous (Kig ad Butler 1985). Legth frequecy data were aalysed to estimate growth of each sex, accordig to the method of Pauly (1983). Legth frequecies of samples from Table IV: Statistical data o the size of the shrimps examied Parameter Males Females Number of observatios Mea size (CL, mm) Rage (mm) No-ovigerous shrimps Ovigerous females September 1990 (for males) ad Jue 1992 (for females) were repeated over five ad six years respectively to simulate the time sequece of the samples accordig to the priciples of Pauly s method. The Hasselblad s maximum likelihood method was used to separate the ormal distributio of mixtured samples. The growth performace of both sexes (Muro s phi prime) was compared, accordig to Sparre et al. (1989). Normality of the legth data was determied usig the Kolmogorov-Smirov test (Sokal ad Rohlf 1981) prior to comparig the mea size of differet groups of shrimps. The same test was used to compare legth frequecy distributios. The Ma- Whitey U test was applied as a o-parametric test to compare idepedet samples (Sokal ad Rohlf 1981). Sex ratios were aalysed by size-class. The relatioship betwee CL ad W was calculated for each sex (or group) over the etire study period usig the equatio W = acl b. RESULTS P. edwardsi has bee caught at depths from 54 m (cruise Gomera 9009 ) to 468 m (cruise Caarias 85 ) i the waters aroud the Caary Islads. Maximum estimates of abudace rage betwee 264 ad 353 g. trap 1 for total shrimps ad betwee

7 1997 Sataa et al.: Life History of Plesioika edwardsi aroud Caary Islads 45 Fig. 6: Relatioship betwee sex ratio frequecy (females x 100/(males + females) ad size of P. edwardsi off the Caary Islads 127 ad 164 g. trap 1 for ovigerous females. These catches were take from depths ragig from 151 to 300 m (Fig. 1). The P. edwardsi populatio was cocetrated betwee 250 ad 300 m deep (total shrimps = 491 g.trap 1, ovigerous females = 168 g.trap 1 ) durig the period Jauary March. The populatio was more homogeeously distributed from April to Jue, whe it occurred over a wider depth rage of m (total shrimps = g. trap 1, ovigerous females = g. trap 1, Fig. 2). Durig the moths July- September, P. edwardsi was cocetrated at m (total shrimps = g. trap 1, ovigerous females = g. trap 1 ). Although the populatio occupied a wide depth rage ( m) from October to December, it was most abudat at m (total shrimps = 721 g. trap 1, ovigerous females = 300 g. trap 1, Fig. 2). Females carried eggs throughout most of the year, with the percetage of ovigerous females i the populatio varyig betwee 9.2 ad 50.4% i May ad July respectively (Fig. 3). The sexual maturity curve for female P. edwardsi (Fig. 4) shows that maturity (25% of the populatio) was reached at 26 mm CL. The distributio of the mea shrimp sizes over each depth iterval durig each seaso is preseted i Table III. I geeral, the size of females (both o-ovigerous idividuals ad ovigerous females) teded to icrease with icreasig depth. However, this tred was ot apparet durig the secod quarter of the year for shrimps caught betwee 301 ad 350 m deep. There was o clear tred i males because of isufficiet data. The legth statistics of the shrimps examied by sex ad reproductive group are summarized i Table IV. Material collected from aroud the Caary Islads raged i legth from 8 to 40 mm CL, ad shrimps betwee 20 ad 29 mm CL represeted 66% of the total sample (Fig. 5). Males raged from 8 to 34 mm CL ad females betwee 8 ad 40 mm CL. No-ovigerous shrimps raged from 8 to 35 mm CL ad ovigerous females betwee 13 ad 40 mm CL (Fig. 5). There were sigificat differeces i the legth frequecy distributios of P. edwardsi by sex ad group (Table V). Females were sigificatly larger tha males (25.3 mm ad 19.1 mm CL respectively), whereas ovigerous females were sigificatly larger tha o-ovigerous idividuals (27.1 mm ad 21.2 mm CL respectively). Females domiated the bigger legth-classes ( mm), whereas sexes were equally represeted i the mm legth rage (Fig. 6). It was ot possible to determie sex ratios i the smaller legth-classes ( mm). Aalyses of the legth frequecy data showed the presece of four modes i males ad five i females (Table VI). Subsequet aalysis of modal progressio provided differet values of L (25.75 ad mm) ad K (0.55 ad 0.69 year 1 ) for males ad females respectively. Based o the phi prime idex, females (Φ = 2.74) seem to have faster growth rates tha males (Φ = 2.56). Table VII lists the relatioships betwee carapace legth ad wet mass for each sex ad group. Mass Table V: Statistical compariso of legth distributios ad mea sizes of shrimps examied Number of observatios Number of observatios No-parametric test Z p Z p Males Females No-ovigerous Ovigerous shrimps females Kolmogorov-Smirov *** *** Ma-Whitey U *** *** z = Desity fuctio of ormal probability *** p < 0.001

8 46 South Africa Joural of Marie Sciece Table VI: Normal legth distributios of male ad female P. edwardsi derived by the maximum likelihood method Number of observatios SI = Separatio idex Mode (CL, mm) icreased with egative allometry, the coefficiet b varyig betwee ad All relatioships were sigificat (p < 0.01) ad the high r 2 values idicated a good fit to the data. DISCUSSION SI χ 2 df Males Females Off the Caary Islads, P. edwardsi has bee collected from 54 m to at least 468 m, maily from 150 to 300 m. The species is commoly caught betwee 250 ad 380 m off the Mediterraea coasts (Holthuis 1987) ad at m off the coast of North Africa (Crosier ad Forest 1973). Although the preset results suggest that P. edwardsi ihabits shallower waters aroud the Caary Islads, it has bee recorded from equally shallow water aroud the Azores (Martis ad Hargreaves 1991). The other commo padalid shrimps, P. arval, is most frequetly caught betwee 20 ad 200 m off the Caary Islads, maily from 50 to 175 m (Gozález et al. 1997). The preset results suggest that P. arval may be replaced by P. edwardsi with icreasig depth. P. edwardsi teds to cocetrate i deep water i witer, moves shallower durig sprig, reaches its shallowest depths i summer ad returs to deep water agai i autum. A similar distributio patter, based o seasoal vertical movemets, has also bee reported for P. arval off the Caary Islads (Gozález et al. 1997) ad i the Easter Mediterraea (Thessalou-Legaki et al. 1989). Ovigerous females of P. edwardsi were preset throughout most of the year, with peak spawig activity from April to September. Ovigerous females of this species were observed betwee Jauary ad 3 10 Table VII: Regressio statistics (y = ax b ) for the relatioships betwee carapace legth (CL, mm) ad wet body mass (g) by sex ad reproductive group of P. edwardsi Sex/Group a ( 10-4 ) b r 2 Males Females No-ovigerous shrimps Ovigerous females For all regressios p < March off the Azores (Martis ad Hargreaves 1991), from Jauary to August off the Iberia Peisula (Zariquiey Álvarez 1968) ad throughout the year i the Mediterraea (Holthuis 1987). Wide spawig seasos have also bee reported for some cogeeric species: P. arval off the Caary Islads (Gozález et al. 1997), P. heterocarpus off the Mediterraea coasts (Holthuis 1987) ad P. martia i the Mediterraea ad the Easter Cetral Atlatic (Zariquiey Álvarez 1968, Lagardère 1981, Holthuis 1987). Give the seasoal ature of both distributio ad spawig patters i P. edwardsi, it is likely that the vertical movemets of the populatio could be related to reproductio. Most shrimps, particularly ovigerous females, ihabit shallower waters durig the secod half (July to September) of the mai spawig period. A similar patter has bee observed for P. arval off the Caary Islads (Gozález et al. 1997). These migratory ad reproductive patters become more difficult to iterpret whe aalysig the bathymetric distributio i relatio to shrimp legth. Off the Caary Islads, the size of female P. edwardsi appears to icrease with greater depth. A similar tred has bee reported for other padalids, e.g. P. arval, Padalus borealis, Padalus motagui, Heterocarpus laevigatus, Heterocarpus sibogae ad H. esifer, where larger idividuals occupy deeper waters (Thessalou-Legaki 1989, Gozález et al. 1997). I the preset study, P. edwardsi showed o size gradiet with depth i relatig to spawig seaso. No-retur migratios towards deeper waters are believed to be the reaso for such size differeces i the ishore/offshore distributio of padalids (Thessalou-Legaki et al. 1989). The observatio that female P. edwardsi are larger tha males ad that ovigerous females are larger tha o-ovigerous idividuals has bee reported for shrimps off the Seychelles (Itès ad Bach 1989) ad the Azores (Martis ad Hargreaves 1991). The predomiace of females i the large size-classes suggests that P. edwardsi might be a protadrous

9 1997 Sataa et al.: Life History of Plesioika edwardsi aroud Caary Islads 47 hermaphrodite, as has bee reported for may tropical ad temperate deep-water padalids, e.g. Padalus daae, Padalus jordai, P. borealis, H. esifer, H. laevigatus ad H. sibogae (Kig ad Moffitt 1984, Thessalou-Legaki et al. 1989). However, the results are ot coclusive. That females are larger tha males ad sex ratios favourig females i larger size-classes have traditioally bee used as evidece for sex reversal. However, similar variatios i size ad sex ratios ca occur i dioecious species where there are sex differeces i relatio to growth, mortality, migratio ad habitat preferece. Differeces i size ad sex ratios appear to have bee icorrectly used to support the hypothesis of sex reversal i other crustaceas (Kig ad Moffitt 1984). Growth parameters calculated i this study, particularly for females, are similar to those reported for P. edwardsi off the Fiji Islads (Kig 1986) ad the Seychelles (Itès ad Bach 1989). The preset data show marked differeces i growth patters betwee the sexes where females have higher growth rates tha males, which accouts for the observed patters of sizes ad sex ratios. Gozález et al. (1997) foud similar sex differeces i relatio to size, sex ratio ad growth patters i P. arval off the Caary Islads. The data preseted here regardig seasoal migratios, sex ratios ad growth suggest that P. edwardsi is dioecious. Therefore, the species coforms to the reproductive patter of tropical padalids ad demostrates the complex ature of their life history. ACKNOWLEDGEMENTS The assistace of our colleagues, Mr V. Rico ad Ms M. García, is gratefully ackowledged. Part of the study was carried out uder the auspices of the Commuity Research Programme, with fiacial support from the Europea Commissio. LITERATURE CITED BISCOITO, M. J A accout of the shrimps of the family Padalidae (Crustacea, Decapoda, Caridea) i Madeira waters. Cour. Forsch.-Ist. Seckeberg 159: CALDENTEY, M. A., SANTANA, J. 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