Local environment and fragmentation by drought and damming shape different components of native and non-native fish beta diversity across pool refuges.

Pool refuges are critical for maintaining stream fish diversity in increasingly intermittent streams. Yet, the patterns and drivers of beta diversity of native and non-native fish in pool refuges remain poorly known. Focusing on Mediterranean streams, we decomposed beta diversity of native and non-native fish into richness difference (RichDiff) and species replacement (Repl), and local (LCBD, LCBDRichDiff and LCBDRepl) and species (SCBD) contributions. We assessed the influence of environmental and spatial factors associated with drought and damming fragmentations on beta diversity components and LCBDs, and of local species richness and occupancy on LCBDs and SCBD, respectively. Overall, non-native species showed a more limited occupancy of pool refuges than native fish. RichDiff dominated beta diversity, though it was influenced by drought and damming fragmentations for native fish and local environment for non-native fish. Repl for native fish was slightly influenced by local environment, but for non-native fish was largely driven by drought and damming, albeit with a contribution of local environment as well. LCBD and LCBDRichDiff increased in pools in low order streams for native fish and at low elevations for non-native fish, and with high or low species richness. SCBD was higher for native species with intermediated pool occupancy, but for non-native species with low occupancy. Our results suggest that stream fragmentation may drive native species loss and non-native species replacement in pool refuges, and that environmental filtering may shape non-native species loss. Pools in lower order streams harbouring unique species-rich or species-poor assemblages should be prioritize for conservation and restoration, respectively, and pools at low elevation with unique non-native assemblages should deserve control efforts. We encourage the partitioning of beta diversity and individual analysis of native and non-native fish in intermittent streams, which may be key in stressing the importance of pool refuges in safeguarding native fish diversity.

Condition and size of the non-native pikeperch Sander lucioperca (Linnaeus, 1758) in Portuguese river basins.

We studied life-history traits focusing on the growth and condition of the pikeperch Sander lucioperca to evaluate its phenotypic plasticity when introduced to new environments. Pikeperch is a non-native fish introduced to Iberian freshwater fauna in 1998 that quickly spread to other river basins through human-mediated activities, occupying now a wide variety of habitats along mainland Portugal. Condition (K and SMI), fork length at age, and length-weight relationships were studied for Portuguese populations. Pikeperch fork length for ages 1, 2, 3, and 4 was different between several populations. We applied generalized linear models (GLM) to study the influence of habitat type, latitude, altitude, time after first detection, and fish prey richness on pikeperch populations size at age 4 and condition. We observed higher condition values on populations from lower altitudes at lentic systems more recently introduced. But higher fork length at age 4 was found in populations from higher altitudes, on older populations with higher prey richness. Habitat type, time since first detection, and fish fauna composition are discussed as the main environmental factors explaining the observed phenotypic plasticity with concerns on predatory impact on native fauna.

Broodstock diet effect on sea urchin Paracentrotus lividus (Lamarck, 1816) endotrophic larvae development: potential for their year-round use in environmental toxicology assessment.

The effect of captive broodstock diet on fertilization and endotrophic larvae development of the sea urchin Paracentrotus lividus was assessed. Maize grain and five inert pelleted diets were tested, during a three-month experimental period. Maize flour, wheat flour, soybean flour, maize/wheat flour (MWF) and maize/soybean flour mixes were used as vegetal sources for inert feed. Gonad index, percent egg fertilization and larvae malformation occurrence were compared with the results obtained from wild sea urchins (W). Whole egg total amino acid composition was concomitantly analyzed as a tool to explain eventual endotrophic larvae malformations caused by lack of specific nutrients. For all treatment groups (wild and captive), percent egg fertilization values above 96% were always observed, fulfilling the requisites (70-90%) necessary to conduct environmental monitoring bioassays, according to USEPA (2002). Similar values for normal percent larval development were only obtained from P. lividus broodstock subjected to an inert feeding diet based on a maize/wheat flour mix (85.0±1.45%), in comparison to wild P. lividus (82.5±1.75%). Likewise, no statistical differences on resultant whole egg total amino acid composition were observed between P. lividus fed MWF and wild treatments. Moreover, statistical differences between MWF and all the other captive feeding treatments were found for six out of the seventeen amino acids analyzed. This study demonstrates the possibility to obtain high values for P. lividus endotrophic larvae percent normal development based on broodstock held in captivity as long as an appropriate inert diet is provided.