Kenneth Oliveira

Variation in Population and Life History Traits of the American Eel, Anguilla rostrata, in Four Rivers in Maine

We examined population traits of yellow American eels from nine sites with similar habitat characteristics in each of four rivers in Maine, U.S.A. Migrating silver eels were also collected to compare sex ratio, age and size at migration among the four rivers. Population density and biomass were not significantly different among rivers with mean ranges of 8.4–21.8 eels 100 m−2and 380–1485 g m−2. Pairwise comparisons of the slopes of weight–length relationships of log transformed data (pooled data: intercept = −6.007, slope = 3.094, r2= 0.99, and n = 3116) revealed no significant differences among rivers. Length–age relationships (pooled data: intercept = 87.826, slope = 23.444, r2= 0.76, and n = 2325) also showed no statistically significant pairwise differences in slopes among rivers. In all rivers, sexual differentiation was complete by 270 mm total length and age eleven. The sex ratios of migrating silver eels were not correlated with yellow eel sex ratios among the four rivers. Mean age at migration among the four rivers was significantly different for males only, with a range of 1.3 years. Both sexes had some significant differences in size at migration among rivers, but the biological importance of the differences is tenuous (male range: 15 mm, female range: 36 mm). The yellow and silver eel population traits from these four rivers showed little variation when riverine habitat was isolated. Variations in traits appeared to be greater when eels from non-riverine habitats may have been present.

Sexually Different Growth Histories of the American Eel in Four Rivers in Maine

Abstract Growth histories of yellow-phase American eels Anguilla rostrata collected in four rivers in Maine, were back-calculated from sagittal otolith increments. Our objectives were to first determine whether sexually dimorphic growth rates exist and then compare the growth histories of American eels from four rivers within a geographic region. For female eels, the maximum growth rate was 31.9 ± 1.7 mm/year at age 8, decreasing to 25.1 ± 2.9 mm/year at age 14. Males attained a maximum of 29.8 ± 1.6 mm/year at age 3, decreasing to a minimum of 17.9 ± 1.3 mm/year at age 11. Females grew faster than males after age 4 and had a slower reduction in growth rate with age. These faster growth rates among females were similar in all four rivers. The observed growth rates are not consistent with current life history hypotheses and may indicate an alternative life history strategy. Because female eels benefit from a larger size (i.e., size refuge, increased fecundity, and greater niche breadth), they would benefit...

Spatial trends of dioxin-like compounds in Atlantic anguillid eels

Several temperate freshwater eel stocks have experienced unsustainable declines, yet to be explained. The decline of lake trout (Salvelinus namaycush) in Lake Ontario has been linked to aryl-hydrocarbon receptor agonists such as polychlorinated dibenzo-p-dioxins/dibenzofurans (PCDD/Fs), dioxin-like polychlorinated biphenyls (dl-PCBs), and polychlorinated naphthalenes (PCNs), and the question remains whether eels are affected similarly by these compounds. Concentrations of PCDD/Fs, dl-PCBs, and PCNs were determined in eels collected at seven locations in eastern Canada including L. Ontario, one location in New York, USA, and one location in Flanders, Belgium. Concentrations varied greatly among origins, indicating dissimilar historic loadings to local areas. The risk to eel reproduction was evaluated with 2,3,7,8-TCDD toxic equivalents, and increased by 10-fold from the least to most contaminated site. The risk to eel recruitment from dioxin-like compounds in American eel using available guidelines is low. The development of a more comprehensive model for eel recruitment risk assessment due to dioxin-like compounds, using eel-specific guidelines, is recommended. Toxic equivalents were 5-fold higher when based on mammalian toxic equivalency factors compared to fish values. About half of the eels captured in L. Ontario exceeded the Canadian guideline for fish consumption (20pg TEQ g(-1) ww), but there were no other exceedances in Canada. The current risk to eel consumers in Canada is low overall, except for highly urbanized and industrialized areas.

Effects of recombinant salmon growth hormone on hypophysectomized male Fundulus heteroclitus

Abstract 1. 1. Recombinant salmon growth hormone at doses of 0.8 and 2.1 μg/g significantly enhanced linear growth in hypophysectomized male killifish, Fundulus heteroclitus , over that of controls and a significant regression was found between growth and the logarithm of dose. 2. 2. Bovine growth hormone elicited significant growth enhancement at all three dosages tested (1,4 and 10 μg/g) and a significant log/dose relationship was also observed. 3. 3. Observations on the relative weight of the gonads indicate that whole salmon pituitary extract (25 μg/g) possesses strong gonadotropic activity and that both bGH and rsGH had smaller but significant effects on the gonads. 4. 4. It is suggested that growth hormone may play a subsidiary synergistic role to other pituitary hormones in gonadal development.

Is Cating's Method of Transverse Groove Counts to Annuli Applicable for all Stocks of American Shad?

Abstract A scale aging method was reported by Cating in 1953 for American shad Alosa sapidissima in the Hudson River and subsequently validated by recapturing fish marked and released in the Connecticut River. However, American shad spawn in all major rivers from Canada to Florida and their scales record growth events occurring in three distinct biogeographic provinces. Thus, a single scale aging method may not be applicable across the latitudinal range of this species. To address this concern, scales from American shad from one southern river (the St. Johns), three Middle Atlantic rivers (the Delaware, Hudson, and Connecticut), and one northern river (the Merrimack) were examined. Scales were cleaned, impressed in acetate, and analyzed by the same reader using a digital imaging system. The transverse grooves, the key morphological character used in Catings method, were counted to the distal edge of the freshwater zone and the first three annuli. In most instances, these groove frequencies were statistic...

Evaluation of the 5α-reductase inhibitor finasteride on reproduction and gonadal development in medaka, Oryzias latipes

5-α reductase (5αR) inhibitors have an anti-androgenic effect in mammals because they inhibit the conversion of testosterone to the potent androgen, dihydrotestosterone. Finasteride is a type-2 5αR inhibitor that is used as a human pharmaceutical for the treatment of prostate cancer, benign prostate hyperplasia and male pattern baldness. This study evaluated the impacts of finasteride (50, 500 and 5000μg/L) on the development and reproduction of medaka (Oryzias latipes) exposed continuously over multiple generations (F0, F1 and F2). The exposure was initiated with reproductively mature fish (F0 generation) and continued until the hatching of the F2 generation. There were no significant effects on survival, fecundity or fertility in the F0 (50, 500, 5000μg/L) and F1 (50, 500μg/L) generations. The F1 generation exposed to 5000μg/L exhibited significant mortality. Histopathology of the gonads demonstrated that medaka and pre-clinical species respond similarly to finasteride exposure. Intersex condition and maldeveloped gonads were observed in F0 generation males exposed to 5000μg/L and F1 generation males exposed to 500μg/L. F1 generation males exposed to 500μg/L displayed reduced gonadosomatic index with an increased incidence of testicular degeneration. Males in both generations exhibited an increased incidence of Leydig cell hyperplasia at concentrations ⩾500μg/L. F0 generation females exposed to 5000μg/L exhibited increased gonadosomatic index. An increased prevalence of accelerated post-ovulatory follicle involution was observed in females at concentrations ⩾500μg/L in both generations. The gonadal changes induced by finasteride support the idea that 5-α reductase inhibition impacts androgen signaling in fish. Results from this study are discussed in the context of differential expression of the androgen receptor between species of fish.

Development and characterization of ten polymorphic microsatellite loci in the yellowtail flounder (Limanda ferruginea)

We isolated and characterized a total of 10 microsatellite loci from the Yellowtail flounder, Limanda ferruginea. Loci were screened in 24 individuals, 8 each, from the Georges Bank, Southern New England/Mid Atlantic, and Cape Cod/Gulf of Maine, management areas. The number of alleles per locus ranged from 5 to 23, observed heterozygosity ranged from 0.375 to 0.875, and the probability of identity values ranged from 0.102 to 0.505. These new loci will provide tools for examining existing management stock designations and for determining levels of gene flow between these stocks.

Reproduction, first-year growth, and expansion of spawning and nursery grounds of black sea bass (Centropristis striata) into a warming Gulf of Maine

The views and opinions expressed or implied in this article are those of the author (or authors) and do not necessarily reflect the position of the National Marine Fisheries Service, NOAA. Abstract—The black sea bass (Centropristis striata) is extending its range northward, into a warming Gulf of Maine. Here, we plot the geographic distribution of specific life stages to examine whether spawning and settlement, and therefore productivity, are extending northward. In order to align these life stages with the correct sampling season, we first resolve confusion about the spawning seasonality of this species, by collecting age-0 individuals from coastal waters of southeastern Massachusetts (Buzzards Bay and Nantucket Sound) and aging them by using daily otolith microincrements. Wild-caught age-0 fish (n=381), ranged in size from 32 to 88 mm total length (mean: 53 mm [standard deviation (SD) 11]), and in age from 50 to 129 d old (84 d [SD 16]). They hatched from May 2 to July 21 (June 6 [SD 14 d]), and grew at linear rates from 0.32 to 1.22 mm/d (0.65 mm/d [SD 0.15]). The literature and two 40-year trawl surveys confirm that black sea bass have spawned in Buzzards Bay and Nantucket Sound since the 1880s. Farther north, in the southern Gulf of Maine, spawning has likely occurred in the last 15 years. Settlement has increased about 1°N latitude over the recent 4 decades in association with warming sea temperatures in the southern Gulf of Maine. The black sea bass (Centropristis striata) is an important fishery species in temperate and subtropical latitudes of the western North Atlantic Ocean (Musick and Mercer, 1977; Hood et al., 1994; NEFSC1) and is the only serranid that spawns north of Cape Hatteras, North Carolina (Kendall, 1972). The northernmost stock, subject of this study, has been historically distributed in temperate waters from Cape Hatteras to Cape Cod, Massachusetts (Roy et al., 2012; McCartney et al., 2013; McBride, 2014), but in recent years its range has been extending northward into the colder Gulf of Maine (KleinMacPhee, 2002; Miller et al., 2016). Coastal warming along the U.S. northeast coast is accompanied by the shifting distributions for many marine species (Nye et al., 2009; Per-