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Understanding migratory life histories is critical for the effective management and conservation of migratory species. However, amphidromous migrations (fish hatch in streams, immediately migrate to the sea for a feeding period and return to fresh water as juveniles) remain understudied owing to the difficulties of tracking tiny larval fish. Despite this, it has widely been assumed that amphidromous fish have open, resilient populations, with marine-rearing larvae dispersing widely during their pelagic phase. In the present study we tested the hypothesis that when an alternative freshwater pelagic habitat is available, non-diadromous recruitment will be the dominant process in sustaining amphidromous fish populations, with implications for their connectivity and resilience. Otolith microchemical analyses of five species (three Galaxias (Galaxiidae), two Gobiomorphus (Eleotridae)) from paired systems on the South Island of New Zealand indicated that when a suitable freshwater pelagic habitat existed downstream, non-diadromous recruitment was the primary population-sustaining process, typically contributing >90% of recruits. In addition, not all species recruited from all lakes, indicating the importance of the largely unstudied role of species-specific amphidromous larval requirements. The results of the present study emphasise the need to better understand the dynamics of individual populations of amphidromous fish, and highlight the importance of understanding species-specific early life history requirements to fully understand their distributions and management needs.

Worldwide, human-mediated disruption of river networks by artificial structures negatively affects migratory fish species. To creatively solve part of this problem, we assessed the effectiveness of mussel spat ropes for improving fish passage past perched culvert structures. We used a before–after–control–treatment design to test our hypothesis that relative abundances of ‘young-of-the-year’ migratory fish species would increase following rope installation in a New Zealand stream. Results following remediation indicated a significant three- to four-fold increase in fish abundance relative to a control stream. Although four species (banded kokopu (Galaxias fasciatus), redfin bullies (Gobiomorphus huttoni), longfin eels (Anguilla dieffenbachii) and shortfin eels (Anguilla australis)) were present at both the treatment and control stream sites, the increased fish relative abundance at the treatment site was driven primarily by an increase in ‘young-of-the-year’ banded kokopu. The present study has shown that mussel spat ropes can significantly improve fish relative abundances above severely perched culverts, but may not be effective for all species present. Future use of ropes for evaluating passage efficacy for other species, and for a wider range of barrier situations globally, may greatly extend the application of this cost-effective tool.

Two new lepocreadiid digeneans, Tetracerasta blepta, gen. sp. nov., and Stegodexamene callista, sp. nov., are described from the intestine of the long-finned freshwater eel, Anguilla reinhardtii, in the Brisbane River, Queensland, and from the Australian bass, Macquaria novemaculeata, in the Richmond River in New South Wales. Their life cycles have been elucidated and completed in the laboratory, by means of uninfected hosts. Both lepocreadiid species use the prosobranch gastropod, Posticobia brazieri, as their first intermediate host. Cercariae of T. blepta penetrate and encyst in the pharyngeal muscle, external muscle, and viscera of fishes in the genera Gobiomorphus and Hypseleotris, and in several species of tree frog tadpoles. The cercariae of S. callista are often eaten or accidentally inhaled by several small fishes, including Retropinna, Craterocephalus, Pseudomugiland Ambasszs, and encyst in the pharyngeal muscle and viscera. All developmental stages are described and illustrated.

Twenty-nine stomachs of the large black shag (Phalacrocorax carbo (Linn.)) and 61 of the white-throated or little pied shag (P. brevirostris (Gould)) from the Rotorua-Taupo area were examined. Techniques used to determine the state of digestion and the identification of otoliths are discussed. Stomach content analyses showed that the food of lake-feeding shags in July consisted almost entirely of fish and freshwater crayfish. Bullies (Gobiomorphus sp.) were the most important food fish. Salmonid fish were found in one stomach (P. carbo).