Abundance Of Commercial Species Research Articles

Spatio-Temporal Assessment of Heterogeneity by Logging Intensity in a Federal Concession Area in the Brazilian Amazon

The logging intensity often does not take into account the spatial heterogeneity of the forest volume of commercial native species in the Brazilian Amazon. This study aims to evaluate the spatio-temporal heterogeneity distribution by assessing logging intensity and its effects on the volumetric stock and abundance of commercial species, with a focus on sustainable management practices. This study was conducted in the Saracá-Taquera National Forest in the Brazilian Amazon. Forest inventory data, elevation, and PlanetScope satellite images were integrated into a geographic information system. The information was aggregated into regular 1-hectare cells for the times before, during, and after logging (t0, t1, and t2). The unsupervised classification algorithm k-means with four clusters was used to analyze heterogeneity. Before logging, areas with higher commercial volumes were distant from water bodies, while areas with lower elevation had lower wood stocks. Logging intensity was generally low, concentrating on a few trees per hectare. Logging in the study area revealed a heterogeneous spatial distribution by intensifying in areas with the highest wood stocks. These results suggest that, in addition to the recommended logging intensity according to legislation, forest heterogeneity should be considered by the manager, promoting adaptive strategies to ensure the conservation of forest resources.

Local fishers experience can contribute to a better knowledge of marine resources in the Western Mediterranean Sea

In this study we explore fishers’ perceptions in the Ebro Delta area, Western Mediterranean, throughout structured questionnaires. Specifically, we compare the coherence of information provided by fishers with those resulting by scientific studies in terms of the status of demersal marine resources in the Ebro Delta area; we describe temporal trends of demersal key species in the area with fishers’ perceptions; and we explore the use of Local Ecological Knowledge (LEK) as an alternative data sources to reduce the gap of knowledge on the spatial distribution and temporal trends of sensitive and vulnerable benthic marine species. Our results document important changes in the bottom trawling activity in the study area and in the abundance of commercial species with time according to fishers’ perceptions. Our results mostly match quantitative information from national statistics and stock assessment analyses. In addition, we document important changes in the presence of Vulnerable Marine Ecosystems (VMEs) in the study area due to the by-catch of habitat forming species with time. According to fishers’ perceptions, habitat forming species occur in the area, but were more frequently captured incidentally in the 1980 s and 1990 s. Overall, our study evidences that fisher’s perception represents an important source of complementary information to describe bottom trawling fisheries characteristics and the long-term changes of demersal target species in the Western Mediterranean Sea. Moreover, it highlights that LEK can provide fundamental and additional information on ecosystem changes and it can be a useful tool to increase the knowledge on spatial distribution and on temporal trends of vulnerable benthic species.

Climatic changes in the abundance of anchovy in the Southeast Pacific ocean

The article discusses the issue of the relationship between climate change and the productivity of oceanic ecosystems. The data on the course of the number of commercial populations in the productive zone of the ocean are analyzed. Comparison of data on climate fluctuations and populations of commercial fish over a period of 16 years, which will reveal the conjugation of climate fluctuations and fish productivity. On the basis of the results obtained, a model is proposed for predicting the abundance of a commercial species for several years, depending on the climate. The results obtained provide an answer to the question of whether long-term fluctuations in the abundance of commercial species are influenced by the climate or large-scale fishing.

Trade-offs among forest value components in community forests of southwestern Amazonia

Baraloto, C., P. Alverga, S. Baéz Quispe, G. Barnes, N. Bejar Chura, I. Brasil da Silva, W. Castro, H. Da Souza, I. De Souza Moll, J. Del Alcazar Chilo, H. Duenas Linares, J. Garate Quispe, D. Kenji, H. Medeiros, C. A. Rockwell, A. Shenkin, M. Silveira, J. Southworth, G. Vasquez, and S. Perz. 2014. Trade-offs among forest value components in community forests of southwestern Amazonia. Ecology and Society 19(4): 56. https://doi.org/10.5751/ES-06911-190456

Effect of selective logging on the genetic diversity of Scaphium macropodum

We examined the effect of selective logging on the genetic diversity of Scaphium macropodum using RAPD markers via two approaches: (1) to investigate the immediate effect by studying a same population before and after logging, and (2) to determine the long term effect by comparing two regenerated stands with an adjacent unlogged stand, assuming that they were genetically identical before logging. Results showed no negative immediate impact for the first approach, probably due to the high abundance and heterogeneity of S. macropodum in the compartment investigated. However, for the latter approach, substantial genetic erosion (i.e. 31.5% reduction for Shannon diversity, H) was detected in one of the regenerated stands corresponding to its extremely low tree density for S. macropodum. This implies the possible occurrence of genetic drift and increased inbreeding due to population decline as a result of logging. However, the observed genetic differences among the three sub-populations having prevailed before logging cannot be totally discounted in the second approach. This study also demonstrates the use of tree density as a good surrogate measure of genetic diversity. The present harvesting system in Malaysia based on a general cutting limit need to be refined; the basis for determining cutting limit in a forest management unit should consider abundance of commercial species.

The Effects of Fishing on Coral Reef Fish Abundance and Diversity

The effect of artisanal fishing on the abundance and diversity of coral reef fish assemblages was investigated in the Kisite Marine National Park and Mpunguti Marine National Reserve at Shimoni, Kenya. Fishing is prohibited within the Park whereas in the Reserve artisanal fishing using traditional methods is practised. Visual censuses of six representative reef fish families (Chaetodontidae, Lethrinidae, Lutjanidae and Serranidae in 1992 and 1994, and Labridae and Pomacentridae in 1994 only) were undertaken along 250×10 m band transects on two similar pairs of reefs subject to differing fishing pressure. The abundance of commercial species (Lethrinidae, Lutjanidae and Serranidae) was depressed in the Reserve. The unfished butterflyfishes (Chaetodontidae) and damselfishes (Pomacentridae) also showed a greater abundance in the Park than in the Reserve. However, neither species number nor Shannon diversity (H′) of any of these families was affected by fishing pressure. Possible reasons for these findings are discussed. The abundance of commercial species, though not of non-commercial unfished species, increased significantly in the Reserve between 1992 and 1994, suggesting that the unfished Park may be acting as a source of larvae or supply of emigrating adults for the depleted Reserve. The results are comparable with other recent studies describing the effects of fishing pressure and also with those studies detailing the effects of habitat refugia in coral reef areas.

Fluctuations in Production and Abundance of Commercial Species in the Red Lakes, Minnesota, with Special Reference to Changes in the Walleye Population

The Red Lakes in northwestern Minnesota comprise 275,000 acres of water which support a commercial fishery producing up to 1.5 million pounds of fish per year. Walleye, Stizostedion vitreum vitreum (Mitchill), and yellow perch, Perca flavescens (Mitchill), are the principal species. Statistics for the past 37 years have been analyzed and fluctuations in the abundance of the important species calculated for the 24-year period, 1930–1953. The fishing is carried on exclusively with 3 1/2-inch-mesh (extension measure) gill nets by Chippewa Indians and the catch is marketed through a cooperative fishery enterprise. There have been wide fluctuations in the abundance of principal species but, although fishing effort has increased greatly during the past few years no trends have developed. Changes in walleye abundance have been shown to be independent of changes or levels of fishing effort, and to be determined by strength of individual year classes. Gear competition has no effect on abundance estimates. Strength of year classes is not correlated with size of brood stock, abundance of competing species, or amount of hatchery fish planted. Weather conditions cannot be correlated with observed changes in strength of year classes. Implications for management include provision of adequate prediction of abundance, and annual adjustment of fishing practices to make greatest use of the available stock. Gear limitations should be designed to secure harvest at optimum size of fish and to provide a suitable economic status for the fisherman.