PRocEED[lcs or].He DESERT FIsHEs Cour.JcIL, 1995 Sn“rosruM Voun€)On4I-Rlel$#Df996

Year: 1995 (xxvii)

Abstract

The seasonal feeding habits of San Ignacio killifish Fundulus lima were studied in the oasis of San Ignacio, B4a Califomia Sur. A total of 108 stomach contents were qr-ralitatively and quantitatively analyzed during an annual ryde. The diet is composed of 16 prelrgroups. The most importanl prey groups (biomass and frequenry of occurrence) were diatoms, filamentous green algaes and vascularplanl remains. Diet composition was significantly similar anong size dasses (Schoener’s overlap indei) as well as arnong seasons. Fish prey were frequently observed in killifish specimens >35 mm SL. Population counts of the Devils Hole pupfish (Cyprinodon diabolis Wales, 1930) made later than I January 1977 were considered in the present study. The ffrst counts of the day (n:89) were found to be most consistent if more than one count was made in the same day. When all the available first count values were plotted qgainst time, a sine wave was apparent. Over 65% of the information in the ft:st counts data set could be explained by a linear regression model which used the cumulative date as the trend line and the sine function of the yearly cyde as the pre&ctive (independent) variables. The construction of thisrelatively simple model allovvs determination of deviations from predicted size, and may idendfy the timing of ecolqgical events that have a significant impact on the population. Examination of stand.ardized residuals suggests that events in the early l98o’s had a negative impact on pupfish population size, but that trendis showing signs of reversal. el presente estudio se consideraron t.ff“:.ffJnoblaci6n del Devils Hole pupfis h (Clryrinodon diabolis Wales, 1930) efectuados despu6s de enero Ot aelgzz. Los primeros conteo-s del dfal’tr:se; r. observaron mds consistentes si mas de un conteo era efectuad.o al dfa. ALgraficar los valores de los primerosconteos disponibles contra el tiempo, se obtuvo una onda sinusoidal. Arriba del 65% de la informaci6n en 23

Resumen

Se estudiaron los hiibitos alimenticios estacionales de la sar&nilla de la peninsula , Fundulus lima en el oasis de San Ignacio, Baja California Sur. Se analizaron cualitativa y .o*.tlt u.ramente IOB contenidos estomaceles durante un cido anual. l,a dieta est6 compuesta de 16 tipos de presas, siend.o los m6s importantes en frecuencia y biomas4 las diatomeas, elgas verdes filamenlos“. y .“toi de plantas vasculares. La composici6n de la dieta fue significativamente similar entre clases de talla (fndice de traslape de Schoener) asf como entre las estaciones. Peces presa fueron frecuentemente observados en especimenes de lima >35 mm LP. AlroEnsEr.I, M. E. (Drc &Mm, r.s vcs., ND !il” regression model of the Devils Hore pupfish population, 1977-L99s KEYWORDS: Devils Hole; California; Devils Hole pupfish; linear regression; population dyramics