), respectively, from winter to spring. In addition, the bacterial secondary production to primary production (BSP:PP) ratio decreased from 3.7 to 0.2 in Reloncaví Fjord, suggesting a transition from microbial to classical pelagic food webs. The higher solar radiation and extended photoperiod of springtime promoted the growth of diatoms in a nutrient-replete water column. Allochthonous (river discharge) and autochthonous (phytoplankton exudates) organic matter maintained high year-round bacteria biomass and secondary production. In spring, grazing pressure from zooplankton on the microplankton (largely diatoms) resulted in the relative dominance of the classical food web, with increased export production of zooplankton faecal pellets and ungrazed diatoms. Conversely, in winter, zooplankton grazing, mainly on nanoplankton, resulted in a relative dominance of the microbial loop with lower export production than found in spring. Carbon fluxes and fjord-system functioning are highly variable on a seasonal basis, and both the multivorous trophic webs and the carbon export were more uncoupled from local PP than coastal areas.

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Thirty-five larvae and adults of the paedomophic goby Schindleria praematura were collected around Easter Island, during November 1999. Mean abundance from the five stations where they were caught (n=26) was 10·2 6·1 individuals 1000 m 3 . They occurred only in shallow areas. Oocyte counts ranged from 70 to 110. Otolith examination suggests that adults appear to live no longer than 3 months.

The southernmost Patagonian region constitutes a major glaciered area with a high freshwater input loaded with particulate and dissolved matter. We assessed the relevance of the terrestrial (allochthonous) and marine (autochthonous) matter that permeates into the fjord and channel system and their possible impact on the euphausiid-based food web. A research cruise (CIMAR 16) was conducted from 18 October to 13 November 2010 (austral spring) in the area between Magellan Strait and Drake Passage to study the physical-chemical and biological characteristics of the pelagic food web, as well as the main biological processes linked with the food web. The dominance of phytoplankton within the autochthonous fractions of particulate organic carbon (POC) and the high abundance and bacterivory rate shown by the heterotrophic nanoflagellates suggest an interplay between microbial and classical food webs. Euphausia vallentini showed a moderate grazing impact (3% of the gross primary production) and a daily ration of 18.6%, and the fecal pellet production rate corresponded to 24.5% of the ingestion rate. This species removed heterotrophic prey (67.5%) preferentially over diatoms (32.5%), and the ingested diet was mainly dinoflagellates, tintinnids, crustacean nauplii and centric diatoms. Overall, euphausiids fed preferentially on marine matter, which showed a tight link with the pelagic food web. Congeneric species of the genus Euphausia shared the condition of 'key species' as they constitute a major carbon and energy flow from lower to higher trophic levels and an important part of the POC flux through their active vertical migration and passive fecal-carbon export. KEY WORDS: Chilean Patagonia · Euphausia vallentini · Pelagic carbon flux · Euphausiid dietResale or republication not permitted without written consent of the publisher

To determine the beginning and end of the transition period from larvae to juveniles in anchoveta Engraulis ringens, seven morphometric measurements were carried out in 333 laboratory-reared and 324 field-caught larvae. Measurements of body morphometrics were employed to calculate the six body ratios selected to show transition changes described in this study. The analysis was carried out with 'dummy variables' (variables that take only one of two possible values: 0 or 1) because a single model was used to indicate the point at which the slope changes in piecewise linear regressions. The regression coefficients of the relationship between ratios of morphometric measurements and body length were not significant in any case (P > 0·05) and, accordingly, a discrete length at which the slope changes could not be estimated. The ratio of the measurements according to the age showed two inflections, corresponding to the beginning and end of the transition period. The first inflection occurred between 32 and 64 days (average 46 days); the second inflection occurred between 81 and 149 days (average 107 days). Therefore, the transition period lasted c. 61 days, starting with a high growth rate, continuing with a slower growth phase, and ending with the onset of a new high growth rate period that corresponded to the start of typical juvenile growth. On the basis of these results, it is hypothesized that the transition from larvae to juveniles in E. ringens is determined more by age than body size.

It has been proposed that current levels of ultraviolet B (UVB) radiation could cause lethal or sublethal effects on fish embryos located in the upper layers of the water column. Observed levels of UVB off central Chile (36°S, 73°W) indicate that planktonic fish embryos could be exposed to harmful UVB radiation. From July 2011 to January 2012 embryos from anchoveta (Engraulis ringens) and common sardine (Strangomera bentincki) were used to test experimentally whether the UVB levels in central Chile produce lethal or sublethal effects in epipelagic fish embryos. Simultaneously, whether the embryos might be exposed to harmful UVB levels in the field was investigated. Our experimental results show that UVB may cause a decrease in hatching success, changes in buoyancy and embryonic malformations. These results, along with the observed vertical distribution of embryos and UVB radiation levels in the field during late spring suggest that lethal and sublethal effects may be occurring in the embryos of both species.