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The larval stage of fishes is critical in determining their dispersal, survival and recruitment, but little is known of the larval behaviours and tolerances of amphidromous fishes, particularly in New Zealand. We report the results of a series of observational and experimental studies on bluegill bully (Gobiomorphus hubbsi), including spawning sites and behaviours, larval characteristics at hatch, phototactic responses of larvae, and larval survival at different salinity levels. Spawning primarily occurred in the lower reaches of the river, and larvae from different nests exhibited marked differences in, and trade-offs between, larval characteristics at hatch, potentially affecting larval success. Larvae were positively phototactic to intense light, an unexpected result based on diel drift patterns and international research. Finally, larvae exhibited markedly higher survival rates when reared at intermediate salinities compared to freshwater or seawater, suggesting estuaries may play an important role as nursery grounds for bluegill bully and other amphidromous fish. 相似文献
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Knowledge of stock structure is key for the effective management of any fish species. Amphidromous fish, which live and spawn in freshwater but spend a pelagic larval period at sea, have typically been assumed to disperse widely during their larval phase, resulting in populations being sourced from a single unstructured larval pool. We used otolith microchemical analysis to examine the stock structure of bluegill bully (Gobiomorphus hubbsi), a declining amphidromous eleotrid endemic to New Zealand, along the west coast of South Island, New Zealand. Some drainages – even those in close proximity (c. 20?km) – were readily distinguishable based on otolith trace element concentrations, while little structure was evident between other geographically disparate locations. These results indicate that, at least in some cases, locally retained larvae, rather than a single unstructured larval pool, dominates recruitment. Management of bluegill bully and other amphidromous species must therefore consider the possibility of regionally distinct populations. 相似文献
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Diadromous fish species dominate the New Zealand freshwater fish fauna and make up 15 of the 17 native fish species found on the Taranaki Ring Plain. Trajectories of occurrence in relation to elevation and distance from the sea are described for 11 diadromous and 2 non‐diadromous species using data from the New Zealand Freshwater Fish Database and data collected over the summer of 1997/ 98. Distinctive distributions were found for most of the species related to their differing migratory strategies and abilities. The species were ranked based on components of these trajectories to compare their penetrative ability. Comparison of the ranking methods used revealed they produced similar results. The ranking of the 11 diadromous species in Taranaki relative to each other revealed similar rankings to those for the same species from the West Coast of the South Island. The non‐migratory native fish, Cran's bully (Gobiomorphus basalis), was not found on the western side of the mountain. This distribution is thought to be the result of the local extinction of non‐migratory species in high gradient or unstable streams. 相似文献
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Larval and juvenile fish drifting on ebb tides were collected from early summer to mid autumn at various locations in the Taieri River and Waipori River estuary, South Island, New Zealand. A total of seven species of fish were recorded, however only three species were regularly collected. These were the larval common bully (Gobiomorphus cotidianus McDowall), larval inanga (Galaxias maculatus Jenyns), and postlarval cockabully (Tripterygion nigripenne Valenciennes). Common bully densities were highest in mid January, with the highest densities being recorded drifting out of Lake Waihola. Inanga densities were highest in March and April, with the highest densities being recorded in the channels draining wetland areas where extensive tidal inundation of riparian vegetation occurred. Cockabully were recorded from February to April, mostly at more downstream sites. Inland penetration by marine species was considerable, with two marine species, clingfish (Trachelochismus pinnulatus Forster) and smooth leatherjacket (Parika scaber Forster), being recorded c. 12 km upstream in late summer. 相似文献
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Fish larvae were collected in stream benthic invertebrate drift nets from the Otira River, near Arthur's Pass, New Zealand during a study of benthic drift. They are identified as probably those of koaro (Galaxias brevipinnis Gunther) on the basis of estimates of myomere counts (indicating Galaxiidae or Retropinnidae); by a process of elimination of likely species on the basis of distance up stream, elevation, and habitat characteristics; and by determining fish species in the Otira River tributaries upstream of the sampling location. This comprises the first likely record of emigrating larvae of koaro, a species known to be diadromous by the return migrations from the sea of whitebait juveniles during spring. A newly hatched larva of koaro is described and figured. 相似文献
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