Wysujack K.,Thunen Institute of Fisheries Ecology |
Westerberg H.,Swedish University of Agricultural Sciences |
Aarestrup K.,Technical University of Denmark |
Trautner J.,Thunen Institute of Fisheries Ecology |
And 3 more authors.
Marine and Freshwater Research | Year: 2015
Despite some recent progress, there are still large gaps of knowledge about migration routes and behaviour of European eels, Anguilla anguilla, during their long-distance oceanic migration. To achieve a better understanding of the migration behaviour, 28 large female silver eels were equipped with pop-up satellite transmitters and released at three different locations in the north-eastern Atlantic Ocean and in the Sargasso Sea. The study covers tracking periods between 7 and 92 days. The distance between release point and estimated pop-up position ranged from 40 to 1000km, the mean minimum migration speeds from 1.5 to 17.0km day-1. The eels consistently conducted distinct diel vertical movements (DVM) with daily amplitudes of more than 300m and maximum diving depths of more than 1000m. Eels released in the Sargasso Sea used greater depths and a broader temperature range than individuals released in the Atlantic Ocean closer to the European continent. At least two eels were clearly preyed upon. The transmitters ascended in a considerable range of directions from the release points. Hence, the results of the study did not allow clear conclusions about the detailed location of the spawning site and on the routes of the eels to the spawning grounds. © CSIRO 2015.
Jacoby D.M.P.,UK Institute of Zoology |
Casselman J.M.,Queens University |
Crook V.,TRAFFIC |
DeLucia M.-B.,The Nature Conservancy |
And 8 more authors.
Global Ecology and Conservation | Year: 2015
With broad distributions, diadromous fishes can be exposed to multiple threats at different stages of development. For the primarily catadromous eels of the family Anguillidae, there is growing international concern for the population abundance and escapement trends of some of these species and yet incomplete knowledge of their remarkable life-histories hampers management and conservation. Anguillids experience a suite of pressures that include habitat loss/modification, migration barriers, pollution, parasitism, exploitation, and fluctuating oceanic conditions that likely have synergistic and regionally variable impacts, even within species. In beginning to redress this rather fragmented picture, we evaluated the extinction risk of these species using the IUCN Red List of Threatened Species Categories and Criteria to infer population-wide trends from catch and monitoring data. Here we consolidate and build upon these species assessments by presenting an overview of the current state of global eel data and conservation, categorising the knowledge gaps and geographic regions where resources are needed and discussing future recommendations to improve our understanding of anguillids. We find stark disparity between the quality and length of data available to assess population trends and conservation priorities in temperate and tropical anguillids. Of the 13 species assessed, four were listed as 'Threatened' (Vulnerable, Endangered or Critically Endangered); four were Near Threatened, three were Data Deficient and two were deemed Least Concern. Comparing with other diadromous species, we examine the multiple threats that impact eels during their different life-history stages, highlighting the challenges of applying the Red List Categories and Criteria to geographically-expansive, catadromous and panmictic groups of species. © 2015 The Authors.
Burgerhout E.,ZF screens BV |
Burgerhout E.,Leiden University |
Brittijn S.A.,ZF screens BV |
Kurwie T.,Mahurangi Technical Institute |
And 6 more authors.
BMC Developmental Biology | Year: 2011
Abstract. Background: Studies on artificial hybridization of different Anguilla species were conducted recently, i.e. female A. australis with male A. dieffenbachii, and female A. japonica with male A. anguilla. The existence of these artificial hybrids was however not demonstrated by independent genetic methods. Two species - A. anguilla and A. australis - that are phylogenetically close but have different sexual maturation times (12-25 weeks and 6-8 weeks, respectively), were expected to produce favourable hybrids for reproduction studies. Results: A modification of the protocol for the reproduction of Anguilla japonica was used to produce eight-day Anguilla australis larvae, with a success rate of 71.4%. Thus ten out of 14 females produced eggs that could be fertilized, and three batches resulted in mass hatching. Hybrid larvae from female A. australis x male A. Anguilla survived for up to seven days post fertilization (dpf). The early development of the hybrid showed typical characteristics of A. anguilla tail pigmentation at 50 hours post fertilization (hpf), indicating expression of genes derived from the father. Conclusions: In this paper we describe the first production of hybrid larvae from male A. anguilla and female A. australis and their survival for up to 7 dpf. A species-specific nucleotide difference in the 18 S rDNA gene confirmed that genes from both A. australis and A. anguilla were present in the hybrids. The developmental stages of the hybrid eel embryos and larvae are described using high resolution images. Video footage also indicated a heart beat in 5-dpf larva. © 2011 Burgerhout et al; licensee BioMed Central Ltd.
O'Brien Q.,Mahurangi Technical Institute |
Cooper D.,Mahurangi Technical Institute
International Zoo Yearbook | Year: 2013
Mahurangi Technical Institute (MTI) operates a commercial fish hatchery that conducts aquaculture research, acts as a teaching tool for aquaculture students, breeds native fish for reintroduction projects, and for supply to zoos and public aquariums for display, as well as breeding selected introduced species for biological control of aquatic weeds throughout New Zealand. This research arm has a long and successful history in the breeding and rearing of a number of fish species, including New Zealand native threatened freshwater-fish species. The Shortfin eel Anguilla australis, Giant kokopu Galaxias argenteus, Banded kokopu Galaxias fasciatus, Shortjaw kokopu Galaxias postvectis, Koaro Galaxias brevipinnis, Redfin bully Gobiomorphus huttoni, Common bully Gobiomorphus cotidianus, Giant bully Gobiomorphus gobioides, Cran's bully Gobiomorphus basalis, Freshwater shrimp Paratya curvirostris and Freshwater crab Amarinus lacustris have all been bred successfully at MTI. Of these native species, MTI has successfully closed the lifecycle of Giant kokopu, Banded kokopu, Cran's bully, Common bully, Freshwater shrimp and Freshwater crab. This paper focuses on work so far conducted to close the lifecycle of the Shortfin eel and the Giant kokopu. © 2013 The Zoological Society of London.