SEA STARS (ECHINODERMATA: ASTEROIDEA) IN ROCKY REEFS OF GUADALUPE ISLAND, NORTHWEST MÉXICO

CICIMAR Oceánides, 24(2):161-165(2009) SEA STARS (ECHINODERMATA: ASTEROIDEA) IN ROCKY REEFS OF GUADALUPE ISLAND, NORTHWEST MÉXICO Estre llas de mar (Echi no der ma ta: Aste roi dea) en arre ci fes ro co sos de Isla Gua da lu pe, Nor oeste de Méxi co RESUMEN. El ob je ti vo del tra ba jo fue des cri - bir la es truc tu ra co mu ni ta ria de las es tre llas de mar en Isla Gua da lu pe, (28 N - 29 N), si tua - da al oes te de la Pe nín su la de Ba ja Ca li for nia. La zo na fue vi si ta da en Sep tiem bre de 2008 y se hi cie ron 64 cen sos en 16 si tios (3,200 m 2 re vi sa dos), tan to en áreas so me ras (0 a 10 m) co mo pro fun das (11 a 20 m). A par tir de los con teos se cal cu la ron los des crip to res co mu - ni ta rios de den si dad y ri que za, di ver si dad (H') y uni for mi dad (J'). En la is la so lo fue ron ob - ser va das las es pe cies Astrometis sertulifera, Pi sas ter gi gan teus y Linc kia co lum biae. El nú - me ro to tal de in di vi duos en con tra dos fue de sie te y da da la ba ja abun dan cia, no se de tec - ta ron di fe ren cias sig ni fi ca ti vas en tre si tios o ni - ve les de pro fun di dad con nin gu no de los ín di ces. No hay ex pli ca ción pa ra el ba jo nú me - ro de es tre llas de mar en la zo na de tra ba jo, pero con si de ran do los ba jos nú me ros de las po bla cio nes y que Isla Gua da lu pe es una Re - ser va de la Bios fe ra, se re co mien da no otor - gar per mi sos pa ra ex trac ción de es tre llas de mar en la zo na, da do que las es pe cies en con - tra das for man par te del mer ca do de es pe cies de or na to. Reyes Bonilla, H., S. González Romero & A. Mohedano Navarrete. Uni ver si dad Au tó no - ma de Ba ja Ca li for nia Sur. De par ta men to de Bio lo gía Ma ri na. A. P. 19-B, CP 23080. La Paz, B.C.S., Méxi co. Tel. (612) 123-8800 Fax:(612)123-8819. email: hre yes@uabcs.mx Reyes Bo ni lla, H., S. Gon zá lez Ro me ro & A. Mohe da no Na va rre te. 2009. Sea stars (Echi no der ma ta: Aste roi dea) in rocky reefs of Gua da lu pe Island, Nort hwest Mé xi co. CICIMAR Oceá ni des, 24(2):161-165. Infor ma tion on reef-as so cia ted sea stars (Echi no der ma ta: Aste roi dea) in the Me xi can Pa ci fic is de tai led for tro pi cal en vi ron ments as evi den ced by nu me rous spe cies lis tings (Ho - ney-escan dón et al., 2008), ta xo no mic mo no - graphs (Cin tra-buen ros tro, 2001), and da ta on com mu nity struc tu re (He rre ro-pé rez rul et al., 2008). Ho we ver, the re is still a dearth of in for - ma tion for tem pe ra te Pa ci fic reefs of Mé xi co, as the re is not a sin gle pa per co ve ring as pects of abun dan ce or dis tri bu tion of this fau na, but iso la ted re fe ren ces and re cords from dred ges and trawls mostly con duc ted in the early and mid-1900s (Ma luf, 1988). The study of sea stars in sub tro pi cal and tem pe ra te en vi ron - ments is re le vant be cau se their usually high num bers and bio mass, com bi ned with their va - ried diet that allows them to in te gra te se ve ral trop hic guilds (from de tri ti vo res to car ni vo res), ma kes them a key ele ment in energy trans fer along trop hic webs (Mi che li & Hal pern, 2005). The ob jec ti ve of this pa per is to im pro ve our un ders tan ding of the tem pe ra te star fish as sem bla ges in wes tern Mé xi co by analy zing the com mu nity struc tu re of this ta xon at the ocea nic Gua da lu pe Island (Fig. 1), lo ca ted 270 km west of the Ba ja Ca li for nia Pe nin su la. This area was de cla red a Biosp he re Re ser ve in 2005, and has be co me fa mous by the pre - sen ce of healthy po pu la tions of ma ri ne mam - mals, birds and whi te sharks, as well as an im - por tant fis hing ground for aba lo ne, lobs ter, sea cu cum bers and ot her re sour ces (San tos del Pra do & Pe ters, 2008). The field work was per - for med du ring a six days vi sit (Sep tem ber 19-24, 2008). We con duc ted vi sual sur veys in 16 si tes around the is land (Fig. 1). At each si te we counted sea stars in si de 25 x 2 m belt tran - sects, pla ced pa ra llel to the coast li ne and at two depth le vels: sha llow (-2 to -10 m depth), and deep (-11 to -20 m); as the pro to col in - vol ved two tran sects at each deph/si te, the re was a to tal of 64 cen sus, co ve ring a to tal reef sur fa ce of 3,200 m 2. From the se da ta we cal - cu la ted the fo llo wing eco lo gi cal in di ces: po pu - la tion den sity abun dan ce (in di vi duals per 50 m 2 tran sect), rich ness (num ber of spe cies per tran sect), Shan non's di ver sity (H, ba se 10), and Pie lou even ness (J ) as well as their ave - ra ge and stan dard errors for the is land. We plan ned to per form sta tis ti cal tests with all eco - lo gi cal va ria bles in or der to com pa re among si - tes and bet ween depth le vels, ho we ver the num ber of star fis hes found in the tran sects was so low (see be low) that it pre clu ded the ap pli ca tion of any test. Fe cha de re cep ción: 10 de agosto, 2009 Fe cha de acep ta ción: 07 de octubre, 2009

162 REYES-BONILLA et al. the south (San tos del Pra do & Pe ters, 2008), a pro ba ble con se quen ce of the di rect ef fect of the Ca li for nia Cu rrent. Fi nally, when con si de - ring depth le vels L. co lum biae and P. gi gan - teus we re found only bet ween 2 and 10 m, whi - le A. sertulifera ap pea red only in the deep zo - ne (> 10 m). Figure 1. Gua da lu pe island, Mé xi co, in di ca ting the lo - ca tions that we re sur ve yed in Sep tem ber 2008. Bo xes indicate the si tes whe re sea stars we re ob ser ved. We ob ser ved only three spe cies of sea stars at Gua da lu pe Island: Linc kia co lum biae Gray, 1840, Astro me tis ser tu li fe ra (Xan tus, 1860) and Pi sas ter gi gan teus (Stimp son, 1857). Accor ding to Ma luf (1988) the first two ta xa ha ve a dis tri bu tion span from Ca li for nia (U.S.A) to the Ga lá pa gos Islands (Ecua dor), and the lat ter ran ges from Van cou ver Island (Ca na da) to Ce dros Island (Mé xi co). Only se - ven in di vi duals we re found in the 64 tran sects (ave ra ge of 0.109 ± 0.050 ind/50 m 2 ); four of them we re A. sertulifera, which was the most abun dant spe cies (0.062 ± 0.038 ind/50 m 2 ) and ap pea red at La Ve la and La Cos ti lla (nort - heast sec tor of the is land). Of the re main der, L. co lum biae (ave ra ge of 0.016 ± 0.016 ind/50 m 2 ) we re seen at Pun ta del Ti bu rón (west), and P. gi gan teus (ave ra ge of 0.031 ± 0.021 ind/50 m 2 ) at Pun ta del Ti bu rón and Cam po Nor te. La ti tu de may ha ve in fluen ce on the pre - sen ce of the sea stars as no in di vi duals we re sigh ted south of 29 N (Fig. 1). This trend points out to a com mon pre fe ren ce of the se as te roids to li ve in lo wer tem pe ra tu res be cau - se sea sur fa ce tem pe ra tu re in Gua da lu pe Island is about 1 C col der in the north than in The fi gu res pre sen ted abo ve are re markably low. As a com pa ri son, L. co lum biae has a den sity of 0.13 ind/ 50 m 2 in the Ga lá pa gos Islands (Edgar et al., 2004), about eight ti mes hig her than at Gua da lu pe, and P. gi gan teus po pu la tions in Ca li for nia can be at least one or der of mag ni tu de den ser (Bom kamp et al., 2004). It is very dif fi cult to as sess why sea stars we re so un com mon at Gua da lu pe Island sin ce P. gi gan teus and A. sertulifera are vo ra - cious car ni vo res of mo llusks, sea ur chins and even fis hes (Schmitt, 1982), all of which are abun dant in the study area, whilst L. co lum - biae is a de tri ti vo re (Cin tra-buen ros tro et al., 2008). Lack of sui ta ble ha bi tat for the spe cies is not the ans wer as they are ge ne ra lists and can be found in mus sel beds, kelp beds, and even in rock ba rrens (Ric ketts et al., 1992). Anot her pos si bi lity is that Gua da lu pe Island is lo ca ted qui te near of the nort hern or sout hern dis tri bu tion li mit of the three spe cies (Ma luf, 1988), and the sub op ti mal en vi ron men tal con - di tions may cau se physio lo gi cal pro blems as tho se re por ted to oc cur in nort hern po pu la - tions of the tro pi cal seas tar Pha ta ria uni fas - cialis (Gray, 1840) in the Gulf of Ca li for nia (Mor gan & Cow les, 1997). Re gar ding pre da - tors, New so me et al. (2009) in di ca ted that P. gi gan teus is pre yed upon by Ca li for nia sea ot - ters, Enhydra lu tris (L. 1758), but ne vert he less this mam mal is ab sent at Gua da lu pe Island, and the re is no re port of anot her sig ni fi cant sea star con su mer known for this lo ca tion. Fi - nally, it is pos si ble that the seas tars carry out a bath yme tric mi gra tion eit her for food, re pro - duc tion, or to avoid war mer wa ter in sum mer, as all the spe cies found are able to in ha bit reefs dee per than -100 m (Ma luf, 1988), and tem pe ra tu re in sha llow wa ter can in crea se se - ve ral de grees du ring sum mer. We sug gest that the most fea si ble ex pla - na tion to our fin dings is that the low po pu la tion den sity ob ser ved re sults from the erra tic re - cruit ment that cha rac te ri zes sea stars, a con -

SEA STARS OF GUADALUPE ISLAND 163 di tion which brings years of re mar ka ble abun - dan ce, and ot hers whe re lo cal po pu la tions can be co me al most ex tinct (Uthic ke et al., 2009). It is no te worthy that in ot her iso la ted is lands of wes tern Mé xi co li ke So co rro and San Be ne - dic to (Re vi lla gi ge do Archi pe la go, 18 N; Re - yes-bo ni lla, 1995) and in the Ma rías Islands (20 N; HRB pers. ob serv., 2007), the num ber of star fis hes is al so qui te low. Pos sibly the suc - cess of the cohorts va ries de pen ding on the strength of the Ca li for nia Cu rrent and the pre - sen ce (or lack of) ed dies around the is land, physi cal fac tors that even tually de ter mi ne if lar vae mo ve away, or re main in si te. The ques - tion me rits furt her in ves ti ga tion but ne vert he - less, the low num bers of sea stars in di ca te that the eco lo gi cal re le van ce of this group in rocky reefs of Gua da lu pe Island should be low, a clear con trast to what is known about the eco - lo gi cal im por tan ce of A. sertulifera and P. gi - gan teus in sout hern Ca li for nia coas tal reefs, whe re their num bers are much hig her. Re tur ning to the da ta analy sis, we found out that the sha llow depth le vel had slightly hig her den sity than the deep one, but the fi - gu res we re qui te si mi lar (0.12 ± 0.07 ind/50 m 2 against 0.09 ± 0.06 ind/50 m 2 ). Ave ra ge as te - roid spe cies rich ness at Gua da lu pe Island was very low (0.09 ± 0.04 sp/50 m 2 ), as well as di - ver sity (H ) and even ness (J ) (0.011 + 0.011 de cits/50m 2, and 0.016 ± 0.016 units res pec ti - vely) be cau se the three in di ces had va lues of ze ro or one (for rich ness) in most tran sects but one, pla ced at 14.5 m deep at Pun ta del Ti bu - rón, whe re one in di vi dual of L. co lum biae and one of P. gi gan teus we re found (re sul ting in H = 0.17 ± 0.17 de cits/50 m 2, and J = 0.25 ± 0.25 units). An exa mi na tion of the li te ra tu re con fir med that only the sea star as sem bla ge from La Entre ga, Oa xa ca (Za mo ra no & Ley - te-mo ra les, 2005) has so low rich ness, abun - dan ce, di ver sity and even ness va lues in wes - tern Mé xi co reefs (Ca so et al., 1996; Re - yes-bo ni lla et al., 2005). As in di ca ted, Gua da lu pe Island is a Biosphe re Re ser ve but not with stan ding the fe de - ral law allows for com mer cial fis hing in the area, al beit li mi ted in vo lu me. Of the three seas tar ob ser ved, Linc kia co lum biae and Pi sas ter gi gan teus are usually sold as sou ver - nirs in cu rio sto res at ci ties like Ma zat lán, Ense na da, Ti jua na, and also in flea mar kets of San Die go (pers. ob serv.). Piña Espa llar gas et al. (2002) and Lunn et al. (2008) do cu men ted some as pects of its tra de. Con si de ring the ex - tre mely low num ber of in di vi duals seen du ring field work, we re com mend the ban of any per - mis sion for cap tu re of seas tars at the is land, as Addes si (1994) has do cu men ted how sen - sitive P. gi gan teus and A. sertulifera are to hu - man per tur ba tion, to the point of ha ving po pu - la tions di sap pear at Ca ta li na Island, Ca li for nia. Our study in di ca ted that seas tar po pu la - tions in sha llow rocky reefs of Gua da lu pe Island are re mar kably low, and con se quently the com mu nity struc tu re of this group is qui te sim ple, cha rac te ri zed by mi ni mal rich ness and di ver sity. The eco lo gi cal ro le of this ta xon must be li mi ted in this ocea nic is land, and we re - com mend that fe de ral aut ho ri ties ban any kind of ex trac tion of spe ci mens in or der to not af fect the po pu la tions. ACKNOWLEDGMENTS This study was con duc ted with sup port from the ad mi nis tra tion of the Re ser va de la Bios fe ra Isla Gua da lu pe (Na dia Cit la li Oli va res Ba ñue los, Di rec tor), and So cie dad Coo pe ra ti - va de Pro duc ción Pes que ra de Par ti ci pa ción Esta tal Abu lo ne ros y Lan gos te ros S.C.L. Artu - ro Aya la and Israel Sán chez (UABCS) co lla bo - ra ted in the field work, and Juan Jo sé Alva ra do (UABCS-Uni ver si dad de Cos ta Ri ca) and two anony mous re fe rees pro vi ded re com men da - tions to im pro ve the con tent and pre sen ta tion of the pa per. REFERENCES Addes si, L. 1994. Hu man dis tur ban ce and long term chan ges on a rocky in ter ti dal com mu nity. Ecol. Appl., 4: 786-797. Bom kamp, R.E., H.M. Pa ge & J.E. Du gan. 2004. Ro le of food sub si dies and ha bi tat struc tu re in in fluen cing bent hic com mu ni - ties of shell mounds at si tes of exis ting and for mer off sho re oil plat forms. Mar. Biol., 146: 201-211. Ca so, M.E., A. La guar da-fi gue ras, F.A. So - lís-ma rín, A. Orte ga-sa las & A. de la Luz Du rán-gon zá lez. 1996. Con tri bu ción al

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