Mather M.E.,U.S. Geological Survey |
Mather M.E.,University of Massachusetts Amherst |
Finn J.T.,University of Massachusetts Amherst |
Pautzke S.M.,Massachusetts Cooperative Fish and Wildlife Research Unit |
And 4 more authors.
Journal of Fish Biology | Year: 2010
Almost three-quarters of the 46 young adult and sub-adult striped bass Morone saxatilis that were acoustically tagged in Plum Island Estuary, Massachusetts, U.S.A., in the summer of 2006 were detected in one or more southern coastal arrays during their autumn migration. On the basis of the trajectories along which these M. saxatilis moved from feeding to overwintering areas, three migratory groups emerged. After leaving Plum Island Estuary, about half of the fish were detected only in a mid-latitude array, Long Island Sound. The other half of the tagged fish were detected during autumn and winter in a more southern array, the Delaware Estuary. This latter group of fish may have used two routes. Some travelled to the Delaware Estuary through Long Island Sound while other fish may have taken a second, more direct, coastal route that did not include Long Island Sound. Consequently, a seemingly homogeneous group of fish tagged at the same time in the same non-natal feeding location exhibited a diversity of southward movement patterns that could affect population-level processes. These three groups that differed in overwintering location and migration route could be movement contingents with migratory connectivity. Journal of Fish Biology. © 2010 The Fisheries Society of the British Isles. No claim to original US government works.
Matsche M.A.,Cooperative Oxford Laboratory |
Rosemary K.M.,Cooperative Oxford Laboratory |
Brundage H.M.,Environmental Research and Consulting Inc. |
O'Herron J.C.,OHerron Biological and Environmental Consulting
Journal of Applied Ichthyology | Year: 2013
Non-lethal sampling techniques were used to document the reproductive structure of the shortnose sturgeon (Acipenser brevirostrum) population at a fish aggregation site (near Bordentown, New Jersey) in the Delaware River. A total of 68 fish were captured using gill nets (100 × 1.8 m, 12.7 or 15.2 cm mesh) and examined laparoscopically in May-June, and 61 additional fish captured and examined in November during 2006-2011. Six stages of reproductive development were identified in females and five stages were identified in males, encompassing differentiation through maturity in both sexes. Fish captured in the spring were predominantly immature with a higher proportion of females (1 : 1.2 M : F sex ratio), while mature males predominated in the autumn (5.7 : 1 M : F), indicating that the Bordentown area serves as an overwintering/pre-spawn aggregation site. Three distinct forms of intersex were noted in gonads of 11.6% of fish examined: ovo-testis, consisting of scattered spermatic cysts in predominantly immature ovary (3.9%); testis-ova, consisting of ovarian lamellae projecting from a predominantly immature testes (4.7%); and zonal distribution, consisting of multiple, nearly-homogenous pockets of either testicular or ovarian tissues along the gonad (3%). The hormone profile in fish with ovo-testis was similar to that of immature males, while the hormone profile in fish with testis-ova was similar to that of immature females. The relatively high prevalence of intersex raises concerns regarding potential reproductive effects and long-term impacts on shortnose sturgeon in the Delaware River. © 2012 Blackwell Verlag GmbH.