Growth, survival and size-selective predation mortality of larval and juvenile inland silversides, Menidia beryllina (Pisces; Atherinidae)

A series of laboratory and field experiments were conducted to determine the relative importance of food limitation and predation as sources of mortality for Menidia beryllina (Cope) larvae and juveniles. Seven-day experiments using in situ mesocosms to exclude predators demonstrated significant growth (mean instantaneous growth rate of 0.122-0.135 day(-1)) and survival (mean 88-89%) for M. beryllina larvae in a Rhode Island, USA, estuary. These results suggest that food was not limiting for growth or survival and, therefore, that predation is likely the primary source of mortality for young-of-the-year (YOY) M. beryllina. Predation experiments were conducted in laboratory aquaria and in in situ mesocosms to assess the size-selectivity of potential predators. Laboratory-reared striped bass, Morone saxatilis Walbaum and field-collected white perch, Morone americana Gmelin, crevalle jack, Caranx hippos Linnaeus and bluefish, Pomatomus saltatrix Linnaeus, were presented with a choice of two or three size classes of laboratory-reared M. beryllina and allowed to feed for 3-24 h. For field-collected predators the experimental prey size range was similar to the size present in the field. Striped bass, white perch and crevalle jack selectively preyed on the smallest size classes. Bluefish, however, selectively preyed on the largest size class. These results suggest that size-specific survival of YOY M. beryllina may vary spatially and temporally depending on the particular suite of predators encountered by individual populations or cohorts. However, in the estuary studied predation mortality appears to be directed towards the larger members of the M. beryllina cohort.