Reproductive biology of common snook Centropomus
Contents
1. 350 gt B x Rainfall y 32 Temperature 3 300 x f E e INE Ao v 30 e d omg E e S E 2004 x V b23 2 j j Y 3 le 2 1504 f 727 5 j ad E V M 26 1004 Y g e 25 50 x 24 0 Y a 23 Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct Dec 2006 2007 Months Fig 4 Monthly variation of the gonadosomatic index GSI for C undecimalis males and females A associated with rainfall and temperature B in the coastal area Tabasco Mexico in Tabasco Mexico Marshall 1958 Peters et al 1998 Taylor et al 2000 Common snook historically occur in the upland rivers streams and lakes during the late fall and winter where they find refuge from large marine predators and forage on ample food reserves Stevens et al 2007 Vast schools aggregate in inlets and around the mouths of coastal rivers during the late spring summer and early fall to spawn However we found reproduction to occur only in the coastal areas during April to Sep tember even though females of mature sizes occur in the riverine areas they showed no reproductive activity which confirms that spawning and reproduction of C undecimalis takes place in the coastal area Stevens et al Rev Biol Trop Int J Trop Biol ISSN 0034 7744 Vol 59 2 669 681 June 2011 2007 Several authors have reported similar results with respect2. 90 80 70 60 50 40 Frequency 30 20 30 35 40 45 50 55 60 65 Fork length cm Females Males 90 95 100 105 110 70 75 80 85 90 95 100 105 110 Fig 3 Sex ratio by length class for the C undecimalis females and males in the coastal A and riverine B areas Tabasco Mexico females only in August 25 and September 33 3 of 2006 First gonadic maturity L In the coas tal area the size at which 50 of the population matured L was recorded at approximately 60cm fork length for males and 80cm for fema les whereas the size of 100 of each sex was mature Loo was estimated at 95cm for males and 100cm for females Fig 7A The average age of sexual maturity A 5 was recorded as 5 5 years for males and approximately 8 5 for females Fig 7B Most males were sexually mature at 11 years of age in contrast females were mature at approximately 13 years of age The size and age of first maturity were not esti mated for the riverine area as only organisms in stages II and III were found DISCUSSION Common snook throughout their range conducts to annual reproductive migrations similar to the patterns we recognize for snooks 674 Rev Biol Trop Int J Trop Biol ISSN 0034 7744 Vol 59 2 669 681 June 2011 1 A 154 i T 1 05 A D A j h A e d 1 d 4d NES 0
3. 671 Each sectioned otolith was read twice and only coincident readings were accepted Beamish amp McFarlane 1983 Taylor et al 2000 Monthly mean between fork lengths of males and females were compared with a Krus kal Wallis non parametric analysis of variance Zar 1999 Sokal amp Rohlf 1996 A multiple correlation and a covariance ANCOVA analy sis were applied to the FL SW regressions to assess differences between sexes Gulland 1983 Sparre amp Venema 1998 The allometric growth equations were obtained with loga rithmic transformations Zar 1999 Sokal amp Rohlf 1996 A t test a 0 05 was used to the value of the slope b to determine the type of 504 454 40 35 304 25 204 Un o I uE growth Ib ez amp Fern ndez 2006 Monthly GSI water temperature and the rainfall were examined with a cross correlation analysis to examine their relationship Pyper amp Peterman 1998 Besides a Chi square X was utilized to compare monthly sex ratio by length class Underwood 1997 RESULTS Size structure The size range of com mon snook collected along the coastal area was 34 to 112cm FL Fig 2A The mini mum average and maximum lengths recorded were 33 7 69 1 and 94 5cm for males and E Male Female 45 Frequency 96 40 35 30 254 Pn om T q o T T 30 65 T T T T 70 75 80 85 90 95 100 105 110 Fork length cm Fig 2 Size fre
4. B av oN Bill m i SS 1 Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul T Aug Sep Oct Nov Dec Months Fig 6 Relative frequency of the maturity stages for C undecimalis females A and males B in the coastal area Tabasco Mexico obligatory but does not occur simultaneously in all males Devlin amp Nagahama 2002 Villamil et al 2002 Hesp et al 2004 Common snook is a synchronous spawner and aggregate near or along the coast during the warmer season when rains initiate the onset of primary production The timing of these annual events provide additional food resources and habitat for successful recruitment which is characteristic of teleosts of the family Centropomidae Peters et al 1998 Taylor et al 1998 Lozano amp Olaya Nieto 2004 Alonzo amp Mangel 2005 Maldonado Garc a et al 2005 Various environmental factors may affect the synchrony of the reproductive process Rev Biol Trop Int J Trop Biol ISSN 0034 7744 Vol 59 2 669 681 June 2011 including the temperature salinity rainfall and full moons Peters et al 1998 Aliaume et al 2005 Shinozaki Mendes et al 2007 According to Wootton 1990 temperature is the most important environmental factor that affects reproduction in fish as it modulates the dynamics of the gonadal cycle and influences the secretion of gonadotropic hormones In this study C undecimalis was found to spawn fr
5. 0 16 para la zona riberefia La relaci n longitud peso no difiri entre sexos en las dos zonas de estudio ANCOVA p 0 05 El periodo m ximo reproduc tivo fue de julio a agosto En la zona costera se encontr una correlaci n significativa entre el IGS y precipitaci n pluvial para machos y hembras r 0 63 r 0 70 en la zona riberefia solo se encontr un correlaci n positiva en las hembras r 0 57 La talla de primera madurez L se estim a los 60cm para hembras y 80cm LF para machos correspondiendo a 5 5 y 8 5 afios de edad respectivamente Los resultados sugieren un cambio en el periodo de explo taci n para la conservaci n de las poblaciones del robalo blanco y su producci n Palabras clave pesquer a din mica poblacional repro ducci n Centropomus undecimalis REFERENCES Aliaume C A Zerbi amp J M Miller 2005 Juvenile snook species in Puerto Rico estuaries Distribution abun dance and habitat description Proc Gulf Carib Fish Inst 47 499 519 Alonzo S H amp M Mangel 2005 Sex change rules stock dynamics and the performance of spawning per recruit measures in protogynous stocks Fish Bull NOAA 103 229 245 Beamish R J amp G A McFarlane 1983 The forgotten requirement for age validation in fisheries biology Trans Am Fish Soc 112 735 743 Braccini J M amp G E Chiaramonte 2002 Reproducti ve biology of Psammobatis extenta J Fish Biol 61 272 288 Brennan
6. 46 13 N 91 09 17 W Samples were obtained monthly from July 2006 to March 2008 total of N 790 coastal area n 323 riverine area n 467 Fork length FL cm somatic weight SW g were measured and sagittal otoliths were removed sex and stage of gonadic maturity were recorded for each individual Sex and sexual maturity were determined using the morphological characteristics and color of the gonad following the criteria established by Vazzoler 1996 Peters et al 1998 and Taylor et al 1998 for sequential spawners Table 1 N o co e N P o J eo ly md o o o o e oO a e e e e N N N N Year Fig 1 Comercial landings of C undecimalis Tabasco Mexico 670 Rev Biol Trop Int J Trop Biol ISSN 0034 7744 Vol 59 2 669 681 June 2011 Stage Indefinite I Inmature II Maturing process III Mature IV Spawning V Restin VI TABLE 1 Macroscopic description of gonadal development stages of C undecimalis Characteristics The sex glands are very thin filaments it is not possible to differentiate males from females Ovaries thin sexing is possible Initiates the development of the gonads the ovaries are pink translucent eggs are not visible to the naked eye Testes in white ribbon both gonads attached to orange brown tissue Ovaries occupy half of the abdominal cavity Gonadic glands are distinct between sexes The ovaries are granular pinkish yellow color s
7. 958 A survey of the snook fishery of Flo rida with studies of the biology of the principal spe cies Centropomus undecimalis Bloch Fla Board Conserv Mar Res Lab Tech Ser 22 McMichael R H K M Peters amp G R Parsons 1989 Early life history of the snook Centropomus unde cimalis in Tampa Bay Florida Northeast Gulf Sci 10 113 126 Motta F S O B F Gadig amp R C Namora 2005 Size and sex compositions length weight relationship and occurrence of the Brazilian sharpnose shark Rhizo prionodon lalandii caught by artisanal fishery from southeastern Brazil Fish Res 74 116 126 Muller R G amp R G Taylor 2006 The 2006 stock assessment update of common snook Centropomus undecimalis Florida Marine Research Institute St Petersburg Florida USA Perera Garc a M A M Mendoza Carranza amp S P ramo Delgadillo 2008 Din mica reproductiva y poblacio nal del robalo Centropomus undecimalis en Barra San Pedro Centla M xico Universidad y Ciencia 24 49 59 Peters K M R E Matheson amp R G Taylor 1998 Repro duction and early life history of common snook Centropomus undecimalis Bloch in Florida Bull Mar Sci 62 509 529 Pinheiro P R 2005 Aspectos reprodutivos do robalo peba Centropomus parallelus na foz do rio doce Linha res es Master Tesis Universidade Federal do Esp rito Santo Vit ria Brasil Pyper B J amp R M Peterman 1998 Comparison of methods to
8. N P M C Darcy amp K M Leber 2006 Pre dator free enclosures improve post release survi val of stocked common snook J Exp Mar Biol Ecol 335 302 311 Caballero C V 2003 Estudio biol gico pesquero del robalo Centropomus undecimalis en el suroeste de 679 Campeche Tesis de Maestria Universidad Nacional Aut noma de M xico M xico D F M xico Campana S E 2005 Otolith science entering the 21 cen tury Mar Freshwater Res 56 485 495 Csirke J 1993 Introducci n a la din mica de poblaciones de peces FAO Roma Italia DeMartini E E A M Friedlander amp S R Holzwarth 2005 Size at sex change in protogynous labroids prey body size distributions and apex predator den sities at NW Hawaiian atolls Mar Ecol Prog Ser 297 259 271 Devlin H D amp Y Nagahama 2002 Sex determination and sex differentiation in fish an overview of genetic physiological and environmental influences Aqua culture 208 191 364 Gilmore R C Donohoe amp D Cooke 1983 Observations on the distribution and biology of east central Florida populations of the common snook Centropomus undecimalis Bloch Fla Sci 46 313 336 G mez G amp R Guzm n 2005 Aspectos de la din mica reproductiva y poblacional del roncador Micropo gonias furnieri en el golfo de Paria estado Sucre Venezuela Zootecnia Trop 23 69 90 Gulland J A 1983 Fish stock assessment a manual of basic methods FAO Wil
9. Reproductive biology of common snook Centropomus undecimalis Perciformes Centropomidae in two tropical habitats Martha A Perera Garcia Manuel Mendoza Carranza Wilfrido M Contreras S ncheZ Maricela Huerta Ort z amp Eunice P rez S nchez 1 Divisi n Acad mica Multidisciplinaria de los R os Universidad Ju rez Aut noma de Tabasco Col Solidaridad S N C P 86901 Tenosique Tabasco M xico martha perera 9 damr ujat mx 2 El Colegio de la Frontera Sur ECOSUR Carretera Villahermosa Reforma Kil metro 15 5 Rancher a Guineo 2a Secci n C P 86280 Villahermosa Tabasco M xico mcarranza ecosur mx 3 Divisi n Acad mica de Ciencias Biol gicas Universidad Ju rez Aut noma de Tabasco 967 Villahermosa Tabasco M xico contrerw hotmail com Received 23 IV 2010 Corrected 08 X 2010 Accepted 08 XI 2010 Abstract In Southeastern Mexico Centropomus undecimalis is an important fish species of sport and commer cial fisheries for coastal and riverine communities Fisheries along rivers and coasts depend on migratory habits of this species and these movements are probably related to reproduction In spite of its economic importance few studies have been conducted focusing on its reproductive biology and this research aims to analyze these habits Samples fork length somatic and gonads weight and macroscopic maturity stages were obtained from organisms collected by fishermen from the largest fishing cooperativ
10. account for autocorrelation in correlation analyses of fish data Can J Fish Aquat Sci 55 2127 2140 Ricker W E 1975 Computation and interpretation of biological statistics of fish populations B Fish Res Board Can 191 1 382 680 Rev Biol Trop Int J Trop Biol ISSN 0034 7744 Vol 59 2 669 681 June 2011 Rodr guez Guti rrez M 1992 T cnicas de evaluaci n cuantitativa de la madurez gon dica en peces AGT M xico D F M xico Sadovy M Y amp M Liu 2008 Functional hermaphroditism in teleosts Fish Fish 9 1 43 Sadovy M Y amp D Y Shapiro 1987 Criteria for the diag nosis of hermaphroditism in fishes Copeia 136 156 SAGARPA 2008 Anuario Estad stico de Pesca 2008 Secretar a de Agricultura Ganader a Desarrollo Rural Pesca y Alimentaci n M xico D F Shinozaki Mendes R A F H H Vieira P O Guilherme amp FC Correia 2007 Reproductive biology of the squi rrelfish Holocentrus adscensionis Osbeck 1765 caught off the coast of Pernambuco Brazil Sci Mar 71 715 722 Siegel V U Damm amp T Neudecker 2008 Sex ratio seasonality and long term variation in maduration and spawning of the brown shrimp Crangon crangon L in the German Bight North Sea Helgon Mar Res 63 339 349 Sokal R R amp FJ Rohlf 1996 Biometry The Principles and Practice of Statistics in Biological Research Freeman New York USA Sparre P amp S C Venema 1998 Introdu
11. and temperature showing that C undecimalis reproduction does not occur in this riverine area The cross correlation analysis showed a three month lag from maximum rainfall to maximum GSI for coastal males r 0 63 and four months for females r 0 70 Fig 5 A B Distribution of sexual maturity stages The largest number of the classified females and males of the coastal area presented stages II and III and these were frequent in most sam pling months Most of mature females stage IV were observed in August 2006 50 and June to July 2007 33 3 and most of matu re males were present in July 2006 48 2 and from May 60 to July 42 8 of 2007 Stage V which represents the maximum spawning period was observed for females in July 2006 25 and in March 12 5 June 16 6 and August 12 5 2007 Fig 6A as well as for males in July 2006 27 5 and July 2007 14 2 The resting phase VI gonads without eggs was observed in females in July 37 5 August 50 and December 36 3 2006 also in February 22 March 25 June 33 July 16 6 and August 12 5 2007 It was not possible to observe this phase in males Fig 6B In the case of the riverine area advanced stages were not observed in either females or males Stage II was predominant during the sampling period Stage III was observed in the 673 100 90 80 70 60 50 Frequency 30 35 40 45 50 55 60 65 70 75 80 85 100
12. ble existence of different stocks in the coastal and riverine areas Future studies must focus on population dynamics reproductive biology migrations recruitment dynamics and fishery demographics to ensure that these biological processes remain in balance with harvest rates to insure healthy local stocks ACKNOWLEDGMENTS The authors thank the fishermen and fis hing cooperatives of San Pedro Barra el Bos que Tres Brazos and San Pedro Balanc n for sharing their data the Consejo Nacional de Ciencia y Tecnolog a CONACyT the Univer sidad Ju rez Aut noma de Tabasco UJAT and the Colegio de la Frontera Sur ECOSUR for financing the study Also we thank Lenin rias Rodr guez and Salom n P ramo Delgadillo for their collaboration and comments Rev Biol Trop Int J Trop Biol ISSN 0034 7744 Vol 59 2 669 681 June 2011 RESUMEN En este estudio se analiz la biolog a reproductiva y poblacional del robalo blanco Centropomus undecimalis El material biol gico se obtuvo en los desembarcos de la pesca artesanal de las cooperativas de mayor contribuci n en la zona costera y ribere a durante julio de 2006 a marzo de 2008 En la zona costera las tallas oscilaron entre 34 a 112cm LF y en la zona riberefia entre 30 a 85cm Se encontraron diferencias significativas entre las longitudes de machos y hembras en ambas zonas de estudio Kruskal Wallis p 0 05 La proporci n machos hembras fue 1 0 68 en la costa y 1
13. cci n a la evalua ci n de recursos pesqueros tropicales Parte 1 manual FAO Santiago de Chile Chile Stevens P W D A Blewett amp G R Poulakis 2007 Varia ble habitat use by juvenile common snook Centro pomus undecimalis PISCES CENTROPOMIDAE Applying a life history model in a southwest Florida estuary B Mar Sci 80 93 108 Tavares L E R amp J L Luque 2003 A new species of Acantholochus Copepoda Bomolochidae parasitic on Centropomus undecimalis Osteichthyes Centro pomidae from the coastal zone of the State of Rio de Janeiro Brazil Mem Inst 98 241 245 Taylor G R H J Grier amp J A Witthington 1998 Spaw ning rhythms of common snook in Florida J Fish Biol 53 502 520 Taylor G R J A Wittington amp HJ Grier 2000 Age growth maduration and protandric sex reversal in the common snook Centropomus undecimalis from the east and west coasts of south Florida Fish Bull 98 612 624 Rev Biol Trop Int J Trop Biol ISSN 0034 7744 Vol 59 2 669 681 June 2011 Tringali M D amp K M Leber 1999 Genetic considera tions during the experimental and expanded phases of snook stock enhancement Bull Natl Res Inst Aquacult Suppl 1 109 119 Tucker J W amp S W Campbell 1988 Spawning season of common snook along the central Florida coast Flori da Scientist Q J Fla Acad of Sci 51 1 6 Underwood A J 1997 Experiments in ecology Their logical design a
14. es along the coastal and riverine areas of Tabasco from July 2006 to March 2008 Fish size ranged from 34 to 112cm fork length with an average age of 6 42 years for males and 9 12 years for females In riverine areas fish sizes ranged from 30 to 85cm and the average age was 5 5 years for males and 6 6 years for females Significant differences were recorded between lengths of males and females from the two areas Kruskal Wallis p 0 05 The male female ratio was 1 0 68 in the coast and 1 0 16 in riverine areas The length weight relationship did not vary between both sexes among areas ANCOVA p gt 0 05 A curve for eviscerated weight was calculated for both sexes for coastal fishes SW 0 0059 FL and the riverine ones SW 0 0086 FL 8 with an isometric growth b 3 The period of maximum reproduction was from July to August with temperatures of 28 to 30 C A significant correlation between the gonadosomatic index GSI and rainfall was recorded for samples of both males and females from coastal areas r 0 63 r 0 70 whereas only one positive correlation was recorded for riverine females r 0 57 The size at first maturity L5 was estimated at 60cm and 80cm FL corresponding to 5 5 and 8 5 years of age for males and females respectively An important proportion of mature females of eight years and older sug gests that these ages contribute significantly to the reproductive biomass The results indicate that due to changes in the exploitat
15. ey Chichester United Kingdom Hesp S A LC Potter amp G N Hall 2004 Reproduc tive biology and protandrous hermaphroditism in Acanthopagrus latus Environ Biol Fish 70 257 272 Ibafiez A A L amp B L A Fern ndez 2006 Manual t cnico de crecimiento relativo y an lisis morfom trico Universidad Aut noma Metropolitana M xico D F M xico Kovacic M 2004 Reproductive biology of the striped goby Gobius vittatus Gobiidae in the northern Adriatic Sea Sci Mar 71 145 151 Lau S R amp P L Shafland 1982 Larval development of snook Centroponus undecimalis Pisces Centropo midae Copeia 3 618 627 Lowerre Barbieri S K F E Vose amp J A Whittington 2003 Catch and release fishing on a spawning aggre gation of common snook does it affect reproductive output T Am Fish Soc 132 940 952 Lozano G E amp C W Olaya Nieto 2004 Reproductive aspects of common snook Centropomus undecimalis in the Cispata Bay Colombia Proc Gulf Carib Fish Inst 55 1029 Luksenburg J A amp T Pedersen 2002 Sexual and geo graphical variation in life history parameters of the shorthorn sculpin J fish Biol 61 1453 1464 Maldonado Garc a M V Gracia L pez M Carrillo A Hern ndez Herrera amp C Rodr guez Jaramillo 2005 Stages of gonad development during the reproductive cycle of the blackfin snook Centropomus medius G nther Aquacult Res 36 554 563 Marshall A R 1
16. ion period we recommend to protect populations of the common snook Rev Biol Trop 59 2 669 681 Epub 2011 June 01 Key words migration reproduction size at maturity Centropomus undecimalis The common snook Centropomus unde cimalis is a tropical protandric hermaphrodite fish with euryhaline and diadromous habits Taylor et al 2000 Tavares amp Luque 2003 Muller amp Taylor 2006 It is distributed from the Western coast of the Atlantic Ocean in North America Florida USA to South Ame rica Rio de Janeiro Brazil including the Gulf Rev Biol Trop Int J Trop Biol ISSN 0034 7744 Vol 59 2 669 681 June 2011 of Mexico and the Caribbean Sea Brennan et al 2006 Zarza Meza et al 2006 A close relationship with rivers and coastal lagoons has been observed for the common snook throug hout its distribution range Peters et al 1998 Aliaume et al 2005 These systems are used by the species for its periodic migrations when it feeds grows and reproduces Stevens et al 669 2007 In Southeastern Mexico C undecimalis is an important species for sport fishing and commercial fisheries for people from coastal and riverine communities Muller amp Taylor 2006 Perera Garcia et al 2008 due to its migratory habits and its size of up to 130cm Tringali amp Leber 1999 Perera Garcia et al 2008 In Tabasco the official catch data for common snook date from 1978 maximum catch were recorded in the last fi
17. mall eggs and opaque with lots of connective tissue Testicles are of an ivory color posterior side is wider than the anterior side It is a long stage Ovaries occupy two thirds of the abdominal cavity The development of the glands is advanced Ovaries are pinkish orange Large and transparent eggs are present Sexual products of females and males are expelled when the specimen abdomen is pressed Testes are whitish and triangular in its entirety Short term phase Ovaries occupy the whole abdominal cavity Ovaries are large plump and bright orange colored sexual products readily to be expelled Well developed veins irrigating the entire gonad Pearly white testes sperm comes out when press lightly Ovaries are enlarged and flabby the product has been expelled Sex glands are swollen and brownish gray Residual eggs are absorbed The fork length somatic weight relation ship Ricker 1975 was calculated separately for the two sexes after the mathematical rela tionship SW aFL where SW is the somatic weight a is the intercept initial growth coeffi cient or condition factor FL is the fork length and b is the slope growth coefficient that indicates the isometric or allometric growth Monthly sex ratios were calculated for the different stages of maturity Gonadosomatic index GSI was calculated according to Rodri guez Guti rrez 1992 GSIZGW SW 100 where GW is the gonad weight and SW is the somatic weight of each indi
18. nd interpretation using analysis of variance Cambridge University Cambridge United Kingdon Urriola M H P J Cabrera amp Q M Protti 2004 Com posici n crecimiento e ndice de condici n de una poblaci n de Poecilia reticulata Pisces Poeciliidae en un estanque en Heredia Costa Rica Rev Biol Trop 52 157 162 Vazzoler A E A 1996 Biologia da reprodu o de peixes tele steos Teoria e pr tica Maring Sao Paulo Brasil Viana F A A Acu a amp E Danulat 2000 Testes mor phology and reproductive aspects of male Brazilian codling Urophycis brasiliensis Kaup 1858 J Appl Ichthyol 16 134 135 Villamil M M J M Lorenzo J G Pajuelo A Ramos amp J Coca 2002 Aspects of the life history of the sale ma Sarpa salpa Pisces Sparidae off the Canarian Archipelago central east Atlantic Environ Biol Fish 63 183 192 Volpe A 1959 Aspects of the biology of the common snook Centropomus undecimalis Bloch of southwest Flori da Tech Ser Fla Bd Conserv 37 1 37 Wootton RJ 1990 Ecology of teleost fishes Chapman and Hall Londres Inglaterra Zar J H 1999 Biostatistical Analysis Prentice Hall New Jersey USA Zar J H 1999 Biostatistical analysis Fourth edition Prentice Hall Englewood Cliffs New Jersey USA Zarza Meza A E J B Villalobos C P V squez amp P T lvarez 2006 Cultivo experimental del robalo Cen tropomus undecimalis Bloch 1792 y chuc
19. ollect the specimens or from differential fishery exploitation DeMar tini et al 2005 Motta et al 2005 because Rev Biol Trop Int J Trop Biol ISSN 0034 7744 Vol 59 2 669 681 June 2011 at high levels of exploitation larger and older fishes are harvested Biological effects and or excessive harvest may lead to a modification of their reproductive strategies decreasing their Ez and increasing their reproduction effort Csirke 1993 Kovacic 2004 Perera Garcia et al 2008 However environmental pressures may also play an important part in the changes in these life characteristics including tempe rature latitude water quality and flooding cycles that occur along natal rivers Urriola et al 2004 G mez amp Guzm n 2005 The potential effects of inordinate harvest pressure must not be overlooked even though historical sizes and ages at first maturity unknown we do know that the fishing pressure on common snook has drastically increased in the states of Tabasco and Campeche in recent years Caba llero 2003 Perera Garc a et al 2008 Future research should focus on determining the sur vival rate for the highly exploited common snook in this region Then an understanding of the complete biology of common snook in this region is fundamental to its population equilibrium and successful management We must conclude a thorough survey of the genetics of the snook population in this region to determine the pos si
20. om three to four months before the heavy rains when temperatures were 26 to 30 C These snooks were stimulated to migrate from the rivers to the estuaries where they form large reproductive groups along the local coas tal regions Peters et al 1998 Aliaume et al 677 Males Females 0 754 e 2 2 oO E O 5 Q 5 dern o o e a 0 25 4 0 20 Proportion of mature T T T 1 12 13 14 15 16 17 9 10 1 Age Years Fig 7 Length A and age B at sexual maturity for C undecimalis males and females in the coastal area Tabasco Mexico 2005 reported that the common snook aggre gate at or near the onset of the rainy season to insure that the requirements for young of the year are in place This strategy guarantees the survival of a greater number of offspring because there is ample available food for small fish in nutrient rich areas Pinheiro 2005 Ste vens et al 2007 The average size and age of first sexual maturity estimated for C undecimalis in the coastal area were approximately 60cm 5 5 678 years for males and 80cm 8 5 years for females These results differ from those repor ted by Caballero 2003 and Perera Garc a et al 2008 but are similar to sizes of snooks in Florida reported by Taylor et al 2000 These differences and similarities in ages and sizes at first sexual maturity from different regions may be the result of different selectivi ty of the gear used to c
21. quency distributions for C undecimalis females and males in the coastal A and riverine B areas Tabasco Mexico 672 Rev Biol Trop Int J Trop Biol ISSN 0034 7744 Vol 59 2 669 681 June 2011 58 2 88 4 and 111 5cm for females respec tively The size range of specimens from the riverine area was from 30 to 85cm FL Fig 2B The minimum average and maximum lengths were 30 62 8 and 88 5cm for males and 54 5 74 and 88cm for females respecti vely Female were significantly larger in both marine KWz112 43 p 0 05 and riverine KW 49 52 p lt 0 05 environments Length weight relationship Length weight relationship were not statistically diffe rent between the males and females for coastal ANCOVA F 1 84 p gt 0 174 and for riverine ANCOVA F 0 46 p gt 0 493 areas Individual length weight equations were coastal females SW 0 0133 FL r 0 88 coastal males SW 0 0045 FL 1220 95 and coastal both sexes SW 0 0059 FL gt riverine females SW 0 0071 FL 220 85 riverine males SW 0 0098 FL 2 gt r 0 90 and riverine both sexes SW 0 0086 FL 2 The b value obser ved for both study areas was not different from three confirming that the growth of C undeci malis is isometric t 1 63 p gt 0 05 Sex ratio The males collected along the coast represented 59 n 192 of the sampled organisms and the females 41 n 131 The overall ratio of male female was 1 46 1 diverging significantly f
22. rom 1 1 X 61 09 p lt 0 001 The greatest proportions of males were observed in July 79 August 77 and November 93 of 2006 and in May 91 and December 70 of 2007 fur thermore females were observed during July 63 and August 73 of 2007 In the case of the riverine area males represented 86 402 and females 14 65 with a male female ratio of 6 18 1 which was different from the expec ted ratio of 1 1 X 26 23 p lt 0 001 Males dominated during the whole sampling period with a greater number of females only in May 53 of 2007 Sex ratio by length class in the coastal area for males showed significant differences X p lt 0 05 between the 30 75cm and the 90cm FL and females of 70 75cm and 90 110cm Rev Biol Trop Int J Trop Biol ISSN 0034 7744 Vol 59 2 669 681 June 2011 FL Fig 3A In the riverine area significant differences were observed in the classes of 30 70 and 80 85cm FL for males and females of 50 70 and 80 85cm FL Fig 3B Gonadosomatic index For the coastal area the monthly average of the GSI of males and females was similar with greater values in July August and September of 2006 and in July and August of 2007 The other months presented low values Fig 4A The maximum GSI values of both sexes were correlated with water temperatures of 26 to 30 C Fig 4B For the riverine area the monthly GSI indicated no reproductive activity and no relationship with rainfall
23. the local fishery focuses on the larger reproductive individuals Hesp ef al 2004 Sadovy amp Liu 2008 Both coastal and riverine areas harbored more males than females however larger females were more abundant in the coastal area in comparison with the riverine area These differences in the sex ratio may be related to reproduction or to sexual differences in growth migratory habits or mortality Selectivity cau sed by type and size of fishing gear may also affect the collection of larger individual males or females Viana et al 2000 Braccini amp Chia ramonte 2002 Siegel et al 2008 but spe cific studies are needed to demonstrate these relationships The predominance of small males in the population is a function of the rate of sex rever sal in the population the absence of males in the larger size classes means that reversal is 676 Rev Biol Trop Int J Trop Biol ISSN 0034 7744 Vol 59 2 669 681 June 2011 100 TII 90 i N 80 Imm 70 NN M 60 50 A 40 30 20 T T T T Jul Aug Sep Oct Nov Dec Jan Frequency 96 e Feb Mar Apr May Jun Jul 100 90 80 H 704 60 504 404 30 4 20 104 o mM mm gt amp VI av DIV Bill m TIERE TTE T Aug Sep Oct Nov Dec
24. to the reproductive period and spawning sites for common snook Mar shall 1958 Volpe 1959 Gilmore et al 1983 MeMichael et al 1989 Taylor et al 1998 Caballero 2003 Perera Garcia et al 2008 Results from this study show that the mean length of females when the sex ratio of the population is 1 46M 1 0F gt 80cm is larger than that of males This is a classic response to the reproductive strategy of a protandric herma phrodite Sadovy amp Shapiro 1987 Taylor et al 2000 Vazzoler 1996 and Devlin amp Nagaha ma 2002 reported that protandric hermaphro ditism is an advantageous reproductive strategy because successful spawning and fecundity 675 Lag i LO ee LE DS Le it NU dU O 0 00 LOWOMNDAUNBRWN O Qo 00 OvUi Jj UN Oo ER o 0 5 0 0 5 1 0 Cross Correlation Coefficient Fig 5 Cross correlation coefficient for GSI and rainfall for males A and females B in the coastal area Tabasco Mexico are of a greater magnitude with higher rates of reproductive success in species with greater lengths than smaller species at comparable ages Common harvest practices of fishermen along the Usumacinta San Pedro and San Pablo rivers take advantage of the reproductive migrations of common snook to collect these larger specimens with nets that obstruct the entire river Perera Garc a et al 2008 Conse quently the wise use of this important resource is in jeopardy because
25. umite Centropomus parallelus Poey 1860 Perciformes Centropomidae en agua dulce en un estanque de concreto en Alvarado Veracruz M xico Vet M x 37 327 333 681
26. ve years of the analyzed time series reaching up to 2 800 metric tons SAGARPA 2008 Fig 1 Despite its economic importance few stu dies have focused on various aspects of the biology of the common snook Previous studies have established the migrations of the species associated with massive spawnings at river mouths Lau amp Shafland 1982 Tucker amp Cam pbell 1988 Peters et al 1998 Taylor et al 2000 Lowerre Barbieri et al 2003 Centropomus undecimalis spawning along the Tabasco coast has been recorded once per year between May and July when migrations among estuaries and freshwater tributaries take place Caballero 2003 Perera Garc a et al 2008 For this reason the main purpose of this study was to describe the reproductive biology of C undecimalis based on samplings from the coastal Gulf of 35004 3000 25004 2000 Landings t 15004 10004 1978 1980 1982 1984 1986 1988 1990 Mexico and the riverine region of the Usumacin ta River in Tabasco and examine the potential relationship between the monthly gonad develo pment and water temperature and rainfall MATERIALS AND METHODS Sampling site Specimens of C undeci malis were obtained from the stocks collected by the artisanal fishery from the coastal area of Barra el Bosque 18 36 52 N 92241 07 W and Barra San Pedro 18 38 59 N 92241 07 W and the riverine area of Tres Brazos 18 23 50 N 92 38 52 W and San Pedro 172
27. vidual The average size and age at sexual maturi ty defined as the size and age at which 50 of the fish are sexually mature L and A and at which all organisms are capable of actively participate in the reproductive process Liq and Aio was obtained from the common snook male and female accumulated relati ve frequencies of macroscopically determined maturity stages between II and V Vazzoler 1996 Luksenburg amp Pedersen 2002 The Rev Biol Trop Int J Trop Biol ISSN 0034 7744 Vol 59 2 669 681 June 2011 values were smoothed with the logistic equa tion of Sparre amp Venema 1998 S L 1 1 eS S2 FD y where S L is the accumulated relative fre quency S1 is the constant or intercept a S2 is the constant or slope b and FL is the fork length cm The age was determined by interpreting growth rings on the otoliths A low speed Buehler IsoMet 1000 saw was used to cut sections approximately 0 5mm thick Taylor et al 2000 Sections were mounted onto clean slides with Crystal Bond 509 thermoplastic cement Electron Microscopy Supply Inc polished and viewed under transmitted light using a stereoscopic microscope fitted with a Cannon Power Shot G6 digital camera Enlarged 7 5 megapixel images were used to enumerate the age marks by two independent readers A translucent band and an adjacent opa que band were assumed to represent one year of growth Taylor et al 2000 Campana 2005
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