Long-lived population demographics in a declining, vulnerable fishery - bigmouth buffalo (Ictiobus cyprinellus) of Jamestown Reservoir, North Dakota

Despite decades of commercial harvest of bigmouth buffalo (Ictiobus cyprinellus) from Jamestown Reservoir, North Dakota, and the recent rapid growth of sport bowfishing that targets this species, there is a lack of biological information on this native catostomid. At present, no-limit recreational and commercial harvest of bigmouth buffalo occurs in North Dakota, with no harvest-reporting for recreational take. A long-lived life history was recently documented for this species with a lifespan exceeding 100 years. At Jamestown Reservoir, bigmouth buffalo were aged to 58 years of age, with onset of sexual maturity 10 years for females. Evidence for episodic recruitment over a 60-year period was in 1962–1979, 1993–2011, and 2017 with recruitment success more likely during non-drought periods. Annual commercial harvest data from this reservoir indicate bigmouth buffalo have declined significantly over the past 30 years, most precipitously since 2010 during the bowfishing era. The demographic patterns, episodic recruitment and harvest changes observed in this population are relevant for informing management of bigmouth buffalo and other long-lived freshwater fishes.

Low clonal propagation in Atlantic and Mediterranean populations of the red gorgonian Paramuricea clavata (Octocorallia)

Clonal propagation is a common feature of benthic marine organisms. In the present study, we investigated the contribution of clonal reproduction in the red gorgonian Paramuricea clavata. Mediterranean populations of P. clavata were severely affected by mass mortality events caused by increased water temperature in 1999 and 2003. The populations are characterized by slow growth and episodic recruitment, but after the observed mortalities, an unexpectedly high recovery rate was observed in the severely affected populations from the Ligurian Sea, NW Mediterranean. Ten years after the last mortality event, we investigated the contribution of clonal propagation in populations from the Ligurian Sea, where some populations were highly affected by mass mortality events, and from the Atlantic, where mortality was never observed. All individuals were genotyped for nine microsatellite loci. The contribution of clonal reproduction varied from 0% to 13% and did not differ significantly between affected and unaffected populations. We confirm by using genetic markers that clonal propagation in P. clavata is not common, and that the contribution of clones is too low to play an important role in red gorgonian reproduction and cannot contribute to population recovery at sites that have been affected by mass mortality events.

Structure of arboreal and herbaceous strata in a neotropical seasonally flooded monodominant savanna of Tabebuia aurea

Large areas in the Pantanal wetland are covered by monodominant formations, e.g. typical landscapes with local names such as “paratudal”, dominated by T. aurea. Studies on structure of these formations generally include only woody strata, consequently the species richness registered is usually low due to the absence of the ‘ground layer’ of herbaceous and others low species. We recorded 13 species, 12 genera and 11 families for the arboreal stratum. Considering arboreal flora without the dominant (T. aurea) individuals showed great establishment in relation to the flood level between 35 – 45 cm while the individuals of the dominant species of 30 – 45 cm. The diameter distribution revealed that the population of T. aurea did not show the reverse J curve, the usual pattern for species in constant regeneration, also evidenced in inconstant Licourt quotient, indicating an episodic recruitment that could lead to future changes in structure. In the herbaceous strata we recorded 78 species, included in 62 genera and 27 families. Using plots method we sampled 46 species, 40 genera and 22 families, while in line interception we found 65 species distributed in 57 genera and 26 families. The floristic similarity of Sørensen between both methods was 59.4%, with 33 species in common, and the method of line interception was more efficient in detecting richness, with 35% more species found in the same time. According to the methods of plots and line interception applied on the woody stratum, our results gave similar detailed information on the structure of this type of savanna, and in spite of being monodominant it shows high species richness when the herbaceous stratum is taken into account. Plots and line interception methods showed similar results for the woody stratum and high species richness of the herbaceous stratum.

Demografia de Syagrus harleyi, uma palmeira acaule endêmica da Chapada Diamantina, Bahia, Brasil

The stemless palm Syagrus harleyi is endemic to the Chapada Diamantina, and the ecology and biology of the species remain unknown. The aim of this paper is to present the results of an analysis of the demographics of S. harleyi in six populations in the Serra do Sincorá, Bahia State, Brazil. We sampled 30 plots of 5 × 5 m. The height and the number of leaves per rosette (ramet identifiable above ground) were recorded. We also recorded the presence of reproductive structures, the length of the sheaths and if the rosettes occur alone or in clumps. It was found 787 rosettes, with 0.98 rosette per m2. No significant differences were detected between populations. The Kolmogorov-Smirnov test found no significant differences in the expected distribution of frequencies of height classes. Most populations had a predominance of intermediate height intervals, but two had a predominantly basal distribution. There were significant differences between sterile and fertile rosettes regarding their height and number of leaves, as well as in number of sheets present in clumps compared to isolated rosettes. The clumps had, on average, 3.91 ± 3.78 rosettes, but two clumps showed 15 and 28 rosettes. The density was found higher than that reported in other works. Studies with other stemless palms also identified the prevalence of intermediate height intervals, a fact credited to episodic recruitment events. However, the vertical growth of the leaves in the early stages of its development can influence plant height. The results indicate that S harleyi may develop as a single rosette or branched individuals forming clumps, which determines four patterns of growth. Comparison with other studies shows that it is difficult to establish ontogenetic patterns in stemless palms, perhaps due to the initial development of these plants, which may occur in the underground.