Main Commercial Species Research Articles

A DSC study of phase transition in muscle and oil of the main commercial fish species from the North-Atlantic

Phase transitions were investigated for Atlantic Salmon, Cod, Herring, Mackerel and Rainbow Trout. The onset of melting was found between −33.5°C and −29.3°C. The amount of unfreezable water was calculated by the DSC (differential scanning calorimetry) melting endotherm integration and was in the range between 5.1% and 8.6% for all investigated samples. The low temperature glass transition was determined to be in the range between −86.0°C and −68.0°C. The high temperature glass transition was found within the melting peak, in the range between −14.0°C and −12.0°C, and was associated with ice melting. Phase transitions of fats, which were present in the fish muscles, did not influence the detection of low and high temperature glass transitions in the samples of fresh fish investigated. The data obtained could be useful to model the freezing process, especially at temperatures below −40.0°C, and the prediction of the fish quality during frozen storage.

A comparison of diel feeding pattern, ingestion and digestive efficiency of Oreochromis niloticus and Oreochromis macrochir in Lake Chivero, Zimbabwe

Possible reasons why Oreochromis niloticus have supplanted Oreochromis macrochir as the main commercial fish species in Lake Chivero, Zimbabwe, were investigated in 2006. Diel feeding trends, daily food consumption and protein digestion efficiencies of the two species were compared. Both followed a similar diurnal feeding trend, with peaks at 12:00 and 16:00. The stomach content dry weight for large fish of 20–30 cm SL peaked in the morning, whereas for small 10–20 cm SL fish it peaked at dusk. Small O. niloticus and O. macrochir fed for 14 h and 12 h, respectively, whereas big fish fed on average for 8 h and 6 h, respectively. Oreochromis macrochir ingested more food than O. niloticus. Small Oreochromis macrochir ingested 2.7 g d−1, which was 53% more than that ingested by O. niloticus of comparable size. Big O. macrochir also ingested 2.7 g d−1, which was 4% more than that of O. niloticus of comparable size. The mean digestive coefficient of proteins ingested by O. niloticus, 62.5% (SD 8.6), was higher than that of O. macrochir, 39.4% (SD 9.1). The efficiency of O. niloticus in utilising food was identified as one of the possible reasons why it had successfully replaced O. macrochir in Lake Chivero.

From small bycatch to main commercial species: Explosion of stocks of rock cod Patagonotothen ramsayi (Regan) in the Southwest Atlantic

The Patagonian Shelf ecosystem is considered to be a wasp-waist ecosystem controlled by medium-sized planktivores Patagonian squid Doryteuthis gahi, rock cod Patagonotothen ramsayi, and southern blue whiting Micromesistius australis. After the collapse of southern blue whiting stocks in 2004–2007, its role was overtaken by rock cod, which exhibited a 20–30 fold increase in catches and CPUEs. P. ramsayi is an important food source for all predatory fish; representing about half of the food consumption in hakes, toothfish, kingclip, and some skates. Its importance increases with increasing size of predator with rock cod gradually substituting a similar-sized squid. The explosion of rock cod abundance coincided with an increase of seasonal immigrants preying on this species (hakes and kingclip) that may have changed their migratory timing and patterns for better use of this food resource.

Gas exchange, phisiological indexes and ionic accumulation in Annona emarginata (Schltdl.) H. Rainer seedlings in nutrients solution

"Araticum-de-terra-fria" (Annona emarginata (Schltdl.) H. Rainer) has been consider a good alternative in rootstock production for the main commercial Annonaceae species. Although this species develops in different soil and climate conditions, there is no understanding by the physiological responses of this species at different nutritional levels. Thus, the objective of this study was to evaluate the influence of different ionic strengths on development of vegetative species known as "Araticum-de-terra-fria". It was evaluated in seedlings grown in different ionic strengths (25% I, 50% I, 75% I and 100% I) of the complete nutrient solution Hoagland and Arnon (1950) nº 2, for 140 days, the following characteristics: Gas Exchange (CO2 assimilation rate, stomatal conductance, internal CO2 concentration, transpiration rate, water use efficiency, Rubisco carboxylation efficiency); Vegetative growth characteristics (diameter, leaf number, dry matter); Physiological Indexes (leaf area ratio, specific leaf area, relative growth rate, net assimilation rate, leaf weight ratio) and Ionic Accumulation (nutrients leaf analysis). Seedlings grown under 50% I showed the highest values of Leaf CO2 assimilation rate, water use efficiency, carboxylation efficiency, growth, relative growth rate, net assimilation rate and ionic accumulation in the total dry matter. So it is concluded that "Araticum-de-terra-fria" seedlings grown under intermediate nutrient concentrations of complete nutrient solution Hoagland and Arnon (1950) nº 2, explored more adequately their physiological potential that justify their adaptation in different nutritional conditions and allow reducing the amount of mineral nutrition of seedlings production.

Nutrient return to the forest floor through litter and throughfall under 7 forest species after conversion from Norway spruce

Tree species can influence nutrient return to the forest floor and nutrient cycling through the amount and chemical composition of throughfall and litter. We compared foliar nutrient concentrations, litter production, nutrient return and soil chemistry under 7 tree species planted on the same site after two generations of a Norway spruce (Picea abies (L.) Karst.) monoculture. Common alder (Alnus glutinosa (L.) Gaertn.), european beech (Fagus sylvatica L.), pedunculate oak (Quercus robur L.), silver birch (Betula pendula Roth.), goat willow (Salix caprea L.) and rowan (Sorbus aucuparia L.) were planted within an experimental catchment on poor acid soil in south-eastern Belgium. Measurements were performed during one year, 11years after planting. This study demonstrated that Ca, Mg, K and N concentrations in foliage and leaf litter are tree-species specific. Fresh foliage and foliar litter N concentrations were highest in alder and willow, while Ca, Mg and K concentrations were highest in rowan. Litter Ca concentrations were approximately twice in rowan than those of all other species. Differences in nutrient concentrations between foliage and leaf litter depended both on the element concerned and on tree species. The total average litterfall biomass ranged from 615kgha−1year−1 under oak to 3122kgha−1year−1 under rowan. Foliar litterfall represented above 85% for beech, spruce and oak, 70% for alder and willow and ca. 55% for birch and rowan. Reproductive parts formed 44% of total litterfall biomass under rowan. Ca, Mg, K and N return via throughfall, foliar litter and reproductive parts were higher under accompanying tree species (alder, birch, willow, rowan) than under the main commercial tree species (oak, beech, spruce). Total N return was in the order of 50kgha−1year−1 under accompanying species, 33kgha−1year−1 under spruce and near 20kgha−1year−1 under beech and oak. Under rowan, total Ca, Mg, and K return to the forest floor through throughfall deposition, litterfall of leaves and reproductive parts amounted to 47, 9 and 66kgha−1year−1, respectively. Compared to spruce, forest floor pHH20 has increased by 0.4 unit under birch and rowan, and exchangeable Ca2+, Mg2+, K+ have increased about threefold under rowan. Planting rowan as accompanying species may therefore represent an interesting management option for improving forest floor chemistry on nutrient poor sites through Ca, Mg, and K nutrient return.

A method for assessing fishers’ ecological knowledge as a practical tool for ecosystem-based fisheries management: Seeking consensus in Southeastern Brazil

Studies on fishers’ ecological knowledge (FEK) and local ecological knowledge (LEK) have rarely been undertaken for practical application in a management context. Here, we describe a methodology to access FEK that was designed under an ecosystem-based fisheries management framework. The procedure was adapted from the Delphi technique, which seeks experts’ consensus, and focused on several spatial and temporal issues related to the small-scale fisheries of the northern coast of São Paulo, Brazil (particularly, in Ubatuba, between 23°20′ S and 23°35′ S). Experienced fishers, considered as experts, were selected during a pilot phase to participate in two sequential rounds of semi-structured interviews at 3 main landing sites and 12 coastal fishing communities. The issues addressed were: (1) spatial and seasonal occurrence of mature females and juveniles of the main commercial species, (2) fishing grounds and bycatch species for each type of fishing gear, and (3) fishers’ suggestions for local fisheries management (e.g. mesh and size of gillnets, closure seasons, gear restrictions by fishing area). It was possible to identify consensus rates on the spatial and temporal issues, as well as on fishers’ management suggestions. The former allowed the construction of maps representing fishing grounds and the local spatial distribution of different fishery stocks strata. We illustrate the output by focusing on five fishery stocks: the seabob-shrimp Xiphopenaeus kroyeri, the whitemouth croaker Micropogonias furnieri, the inshore squid Loligo spp, the white shrimp Litopenaeus schimitti and the blue runner Caranx crysos. Overall, the results provided new guidelines for future local fisheries management and conservation initiatives. The methodology proved to be useful for the definition of essential fish habitats (EFHs), suggesting their potential application in other locations.

角倍蚜虫瘿对盐肤木光合特性和总氮含量的影响

Chinese gallnut which formed by some aphids is a special local product of China and valued as a commercial product for export. Schlechtendalia chinensis is the main commercial species which induces horned gall on Rhus chinensis and its shares about 75% more Chinese gallnut yield of the world. Effects of horned gall on photosynthetic characteristics and total nitrogen content of R. chinensis were analysed in Kunming,Yunnan province. The result indicated that photosynthetic characteristics of R. chinensis were disturbed by the horned gall. Compared to the control plants,( 1) maximum photosynthesis rates( Amax) of the leaves induced gall of treatment plant rose to 14. 49%,32. 17%,and 42. 01% by horned galls in the initial,middle and late gall stages,respectively. Maximum photosynthesis rates of the nearby leaves without gall were also raised but declined after middle gall stage.( 2) light-compensation points( Lcp) of the leaves induced gall were raised,but the Lcp of the leaves without gall were declined in middle gall stages. Light-saturation points( Lsp) of the leaves induced gall were raised,but the Lsp of the leaves without gall were declined in initial and middle gall stages.( 3) dark respiration rate( Rd) of the leaves both induced gall and without gall were raised in the initial gall stages,but no significant influences in the middle and late gall stages. Effects of horned gall on photosynthetic characteristics of R. chinensis leaves were correlated to the leaflet positions and the gall growth stages. At the same time, the total nitrogen content distribution of R. chinensis leaves had been changed by the horned gall. Total nitrogen contents of gall,leaves induced gall and leaves without gall were 1. 13%,1. 98%,and 2. 14%,respectively. It is the possible reasons that nutrition flows to the leaves which induced gall and finally to the galls from leaves without gall,and supplied to the gall and galling aphids need.

Assessment the Present Status of Batticaloa Lagoon, Sri Lanka by means of Water Quality, Fish Diversity Indices and Pollution Indicating Planktons

Abiotic and biotic variables of coastal lagoons are highly heterogeneous in both space and time, and this heterogeneity complicates the assessment of lagoon ecological status. These variables are essential for monitoring and preserving of these fragile ecosystems and the resources and services they sustain. This study was designed to assess the effect of lagoon water quality on changes in fish abundance. In situ measurements of chemical and physical parameters of the Batticaloa lagoons were measured fortnightly by using a calibrated portable Hanna instruments over the different seasons from March 2012 to February 2013. Fish diversity indices for the main commercial species were calculated. Fish composition varied greatly according to the study site and the seasonal trends. Results reveal that the existing conditions, such as salinity dissolved oxygen, nitrate and pH had a strong effect on the fish community in the lagoon. The present study is commissioned to assess the seasonal variation and the status of the lagoon to make informed plans for the fishery of the lagoon patients to reap it successfully and sustainably.

An individual-based model applied to the study of different fishing strategies of Pintado Pseudoplatystoma corruscans (Agassiz, 1829)

The decline in stocks of commercial fish species has been documented in several regions of the world. This decline is due partially to the effect of evolutionary pressure caused by the management of fishing activity, which reduces the size of fish after a few generations. In this paper, the population dynamics of the Pintado Pseudoplatystoma corruscans, one of the main commercial species of freshwater fish in Brazil, were simulated considering different scenarios of fishing mortality and different minimum and maximum lengths of capture. The results show that selective fishing based on the different proposed selectivity curves can result in an evolution-mediated increase in the growth rate of the fish, the biomass and the catch. This suggests that appropriate changes in Brazilian legislation can contribute to the sustainability of fisheries and to conservation of the fish stocks exploited by man.

경상북도 영일만에 분포하는 이매패류의 자원조사

Bivalves collected by a dredge in Yeongil Bay of Gyeongsangbuk-Do Province, Korea in May, 2010 and August, 2010 were 2 species including Dostinorbis japonicus and Scapharca broughtonii. The total abundance of bivalves were 1,703 inds. and 140.9 kg. Among them, the abundance of D. japonicus were 1,198 inds. and 76.1 kg. And the abundance of S. broughtonii were 505 inds. and 64.8 kg. The shell length by bivalves species were 25.76-67.88 mm (mean, 58.08 mm) in D. japonicus and 46.82-113.74 mm (mean, 76.86 mm) in S. broughtonii consisting mainly of recruitment group. By regional abundance comparison, the bivalves abundance collected in the outside harbor was 1,332 inds. and 105.4 kg, which was much more than that of the inside harbor indicating 371 inds. and 35.5 kg. In terms of size, the bivalves collected in the outside harbor were 49.49-67.88 mm (mean, 58.47 mm) in D. japonicus and 48.21-113.74 mm (mean, 77.48 mm) in S. broughtonii, which were larger than those of the inside harbor. The yearly biomass of the main commercial target species, S. broughtonii by swept area method (SAM) was estimated up to 242.1 tons. However, considering the regional differences of bivalves between the inside harbor and the outside harbor by abundance and size comparison, it might have been overfished to bivalves in the inside harbor.

Application of extinction risk and conservation criteria for assessing fish species in the lower La Plata River basin, South America

ABSTRACT The Lower La Plata River basin contains between 160 and 260 native species depending on the river segment, with a few stretches containing locally endemic species. Extinction risk analysis for 185 freshwater fish in the lower La Plata River basin is presented for the first time on the basis of regionally standardized International Union for Conservation of Nature (IUCN) Red List criteria and is compared with alternative methods within the region. There were 11 threatened species (6%), of which three were considered as Endangered and eight as Vulnerable. A further three were rated as Near Threatened; while 121 (66%) were assessed as being of Least Concern, and 49 (26%) remained Data Deficient. The application of regional guidelines after using the global criteria did not change the categories established. The application of the IUCN criteria A and B presented considerable challenges because of insufficient information, with criterion C being inapplicable; whereas criterion D proved valid in five instances where endemic species were found highly restricted in geographical range and only inhabiting small streams. The use of other approaches, such as the Sum of Index (SUMIN) method and the Assessment Method of Threat Degree (MEGA), resulted in only an 11% agreement with the IUCN results for the main commercial and recreational target species. The discrepancies between the IUCN and the other methods may be explained in that the former measures the extinction risk by population decline as the main criterion, whereas the latter two put more emphasis on the assessment of intrinsic vulnerability and the threat status, with these additional criteria being incorporated in order to define conservation priorities. Further research is strongly recommended for the application and improvement of the IUCN regional criteria based on better ecological information, particularly data on non‐target species inhabiting small tributaries, wetlands, and headwaters across the basin. Copyright © 2012 John Wiley & Sons, Ltd.

A reference linkage map for Eucalyptus

BackgroundGenetic linkage maps are invaluable resources in plant research. They provide a key tool for many genetic applications including: mapping quantitative trait loci (QTL); comparative mapping; identifying unlinked (i.e. independent) DNA markers for fingerprinting, population genetics and phylogenetics; assisting genome sequence assembly; relating physical and recombination distances along the genome and map-based cloning of genes. Eucalypts are the dominant tree species in most Australian ecosystems and of economic importance globally as plantation trees. The genome sequence of E. grandis has recently been released providing unprecedented opportunities for genetic and genomic research in the genus. A robust reference linkage map containing sequence-based molecular markers is needed to capitalise on this resource. Several high density linkage maps have recently been constructed for the main commercial forestry species in the genus (E. grandis, E. urophylla and E. globulus) using sequenced Diversity Arrays Technology (DArT) and microsatellite markers. To provide a single reference linkage map for eucalypts a composite map was produced through the integration of data from seven independent mapping experiments (1950 individuals) using a marker-merging method.ResultsThe composite map totalled 1107 cM and contained 4101 markers; comprising 3880 DArT, 213 microsatellite and eight candidate genes. Eighty-one DArT markers were mapped to two or more linkage groups, resulting in the 4101 markers being mapped to 4191 map positions. Approximately 13% of DArT markers mapped to identical map positions, thus the composite map contained 3634 unique loci at an average interval of 0.31 cM.ConclusionThe composite map represents the most saturated linkage map yet produced in Eucalyptus. As the majority of DArT markers contained on the map have been sequenced, the map provides a direct link to the E. grandis genome sequence and will serve as an important reference for progressing eucalypt research.

Status of Two Species of Lac Insects in the Genus Kerria from China Based on Morphological, Cellular, and Molecular Evidence

The taxonomic status of the Chinese lac insects Kerria yunnanensis (Ou and Hong) (Hemiptera: Kerridae) and K. ruralis (Wang, Yao, Teiu and Liang) were analyzed in this paper by comparing morphological, cellular, and molecular data. Cladistic analysis showed K. yunnanensis and K. ruralis to be distinct from other Kerria species such as K. lacca and K. chinensis. The karyotype of K. yunnanensis was 3A and the chromosome structure was K = 6m + 2sm + 10T, while in K. ruralis the karyotype was 3B and the chromosome structure was K = 8m + 10T. Kerria ruralis and K. yunnanensis had the closest relationship among species in the genus as they had the most similar karyotype homology. Based on the karyotype analysis, K. sindica and K. lacca formed a sister group with K. ruralis and K. yunnanensis. Kerria pusana and K. nepalensis were clustered as a sister branch, indicating the close relationship of these taxa. The karyotype of K. chinensis was however, different from the other six species and formed a separate branch. RAPD analysis also showed that K. yunnanensis and K. ruralis had distinct differences from other species of Kerria, although they did not form sister taxa. Molecular analysis based on the EF1α gene using ML, MP, and Mr. Bayes' methods indicated that seven species of lac insects cluster in two major groups. In group 1, K. sindica and K. lacca formed a sister clade and were primitive members of the genus. In group 2, K. chinensis formed the earliest diverging branch followed by K. ruralis. Kerria yunnanensis was the next to diverge followed by the cluster containing K. pusana and K. nepalensis. Hybridization testing showed that crosses neither between K. yunnanensis and K. sindica, nor between K. yunnanensis and K. lacca could produce first generation larvae. This was indicative that K. yunnanensis had a distant genetic relationship from the other species. Morphological, cellular, molecular, and hybridization results confirmed the independent status of the Chinese endemic species K. yunnanensis and K. ruralis. Kerria ruralis was genetically closely related to K. yunnanensis, but relatively far from K. lacca. The main commercial species in China was K. yunnanensis, while in Thailand it was K. chinensis. The commercial species in Myanmar included K. nepalensis and K. pusana, the latter being most widely used in lac production.

Alternative codends to reduce bycatch in Chilean crustacean trawl fisheries

This study was conducted to determine the reduction in bycatch and the loss of target catch in trawl hauls for three commercial crustacean species (yellow squat lobster, Cervimunida johni, nylon shrimp, Heterocarpus reedi, and red squat lobster, Pleuroncodes monodon) in central Chile. Two experiments were carried out using the covered codend method; the first used different mesh sizes (56 and 70 mm, knot-centre to knot-centre) and shapes (diamond and square), and the second tested different reduction devices (escape panel and sorting grid). We analysed the escape proportions of the species caught and the size frequency distributions of the target species and Chilean hake ( Merluccius gayi), the main commercial bycatch species. The results demonstrate that it is feasible to significantly reduce bycatch while keeping losses within acceptable ranges. In particular, the best option for yellow squat lobster was the combination of a 70-mm diamond mesh with an escape panel that reduced non-target and target catches by 48% and 7%, respectively. For nylon shrimp, the best option was the use of a 56-mm diamond mesh with a sorting grid that reduced non-target and target catches by 41% and 11%, respectively. Although the results for red squat lobster were not as promising, they will help to guide future research.

Reproductive biology and some observation on the age, growth, and management of Tilapia zilli (Gerv, 1848) from Lake Timsah, Egypt

In the present investigation, some biological aspects of Tilapia zillii from Lake Timsah were studied. This was carried out on 700 fish samples collected during the period from October, 2002 to September, 2003. Total length of females ranged from 7 to 16 cm and males from 8 to 21 cm. Age determination based on length frequency distributions showed that the life span are two and four years for females and males, respectively. Estimates of growth parameters are widely used for detailed assessment and modeling of fish species and fisheries. The length-weight relationship, age at length zero (to), growth coefficient (K), asymptotic length (L¥) and rates of natural (M) and total mortality (Z) were estimated for T. zillii from Lake Timsah. Length-weight relationships were calculated from individual fish length and weight records collected from sampling using gill nets. Analyses were obtained by sampling direct from the fisher’s catches. Data were analyzed using the FISAT software. T. zillii, the estimate of K was 0.320 and 0.680 year-1 for males and females, respectively, whilst L¥ i€ was approximately 22.05 and 17.85 cm, for males and females, respectively. T. zillii (males) had the lowest value of K and the largest L¥ i€ than females. Natural mortality was the lowest for T. zillii (females) (M=0.464 and 0.38 year-1) and fishing mortality was highest for T. zillii (males) (F=2.656, 1.88 year-1). In addition, exploitation rate was estimated at E=0.83 and length at first capture (Lc) was calculated at 11.30 cm for males while E=0.78 and (Lc) was estimated as 6.68 cm for females. The majority of fish caught of the main commercial species in the Lake Timsah fishery were from the first age group, at a size far below the optimal length at capture. This suggests growth overfishing for T. zillii in Lake Timsah. Key words: Lake Timsah, Tilapia zillii, age and growth, mortality, gonadosomatic index, length at first maturity, population structure.

Rapid Identification of Seaweeds in Food Products by PCR Combined with ALF-RFLP and FINS Methodologies

In the present study, two methods for the genetic identification of the most important seaweed species used for human consumption were developed. Both are carried out through PCR amplification of an 18S rRNA gene fragment. The first one is based on the phylogenetic analysis of DNA sequences (FINS), while the second is based on length polymorphism and RFLP visualized by means of an ALF system. The main novelty of this work lies in the fact that it allows genetic identification of the main commercial species of seaweed. Moreover, the developed systems can be applied to all kinds of processed products, including those that have undergone intensive transformation, as for instance canned foods. These methodologies also permit the detection of species in complex matrixes where more than one algal species is present. The methods were validated using products manufactured in a pilot plant showing correct functioning. Finally, the methods were applied to 23 commercial samples including some that had been subjected to intensive thermal treatment, allowing the detection of those that were incorrectly labeled (30%). Therefore, these molecular tools can be used for clarifying questions related to the correct labeling and traceability of commercial products that include some seaweeds in their composition.

Estoques de carbono no solo e na biomassa em plantações de eucalipto

O eucalipto é a principal espécie florestal plantada no Brasil. Todavia, são escassas informações acerca do C estocado no solo e na biomassa desses plantios. Este trabalho teve como objetivos avaliar o estoque de C no solo (ECS) em plantações de eucalipto e determinar quais características edafoclimáticas determinam esse estoque. O estudo foi conduzido em eucalipto cultivado na região centro-leste do Estado de Minas Gerais, abrangendo cinco regiões: Cocais (CO), Rio Doce (RD), Sabinópolis (SA), Santa Bárbara (SB) e Virginópolis (VI). Foi calculado o estoque de C no solo até 100 cm de profundidade em plantações de eucalipto em áreas com predomínio de seis classes de solo: Cambissolo Háplico (CX), Latossolo Amarelo (LA), Latossolo Vermelho (LV), Latossolo Vermelho-Amarelo (LVA), Neossolo Flúvico (RU) e Plintossolo Pétrico (FF). Os estoques de C no solo variaram entre regiões e classes de solo. O maior ECS ocorreu no LV, com 183,07 t ha-1 de C, seguido pelas classes de CX, LVA, LA, FF e RU, com 135,65, 130,95, 121,58, 112,01 e 95,08 t ha-1 de C, respectivamente. Em relação ao estoque médio de C no solo por região, considerando todas as classes de solo, o maior ECS foi de 141,22 t ha-1; determinado na região de VI, na profundidade até 100 cm de profundidade, seguida pelas regiões SA, CO, SB e RD, com 135,54, 127,26, 112,89 e 80,79 t ha-1 de C, respectivamente. Ao se considerar o estoque de C total no sistema solo-planta, aos 84 meses de idade, a região de SA foi a que apresentou maior estoque, com 251,61 t ha-1; e a região de RD, o menor estoque, com 186,84 t ha-1 de C. O ECS pode ser estimado por equações compostas por características edofoclimáticas, sendo a variação em ECS explicada por características como teor de argila e de Al3+; pela altitude e pelo déficit hídrico da região.

Regeneration of commercial tree species in a logged forest in the Selva Maya, Mexico

One of the main threats to the sustainability of community forestry in the Selva Maya is insufficient regeneration of commercial tree species. We evaluated the regeneration status of 22 commercial tree species in a managed semideciduous tropical rain forest in Southern Mexico. The study was carried out in six harvesting areas along a 16-year chronosequence. In each area, 10 transects (1000 m 2) were established and all trees >50 cm height and <10 cm diameter were recorded. We evaluated the relationships between seedling and sapling abundance, and canopy cover and disturbance condition (closed forest, canopy gap, log landing, skid road, primary road and secondary road). The area occupied by closed forest canopy increased with age of harvesting area (65–91% of sampled area), while the area occupied by canopy gaps decreased (22–9%). Log landings occupied less than 1% of the sampled area. The predominant canopy cover was 75–80% in all harvesting areas, even in the most recently harvested areas. The highest densities of seedlings and saplings, of both shade tolerant and intolerant species, were found in log landing and skid trails, followed by secondary roads. Even Simarouba glauca, a shade tolerant species, displayed higher densities in sites with ≤65% of canopy cover. Our results support previous findings and indicate that the levels of disturbance caused by existing harvesting procedures may be inadequate to promote sufficient regeneration of not only light demanding desirable species but also for some of the evaluated shade tolerant species of commercial interest. Seedling and sapling densities exhibited by Swietenia macrophylla, for example, are insufficient to support current harvesting rates. The application of a spatial mixed system with patch-cuts of different sizes, a consequence of group felling, could be applied to provide the necessary conditions for the regeneration of the main commercial species.

Development of foliage biomass of young spruce and beech stands in the mountain water balance research area

The investigation of foliage biomass development including LAI and the growth of spruce and beech stands in the juvenile stage (age 1 to 21 years) represents a special complementary study to long-term research of water balance components on the experimental forest hydrology area Deštné Mountainside. The experiment is located in the Orlické hory Mts. at the altitude of 900 m on a clear-felled area. In 1982 the spruce plantation was established at 1.5 ´ 1.5 m spacing (4,600 plants/ha) and the beech plantation at 1.0 ´ 1.0 m (10,000 plants/ha). According to tending programs applicable to forest stands in the Czech Republic, two improvement fellings were carried out (1995 and 2001) in spruce and none in beech. In 2002, some 1,550 spruce trees/ha (mean height 10.1 m) and 7,440 beech trees/ha (mean height 4.8 m) were recorded. At the end of the first vegetation season in 1982, the dry matter (DM) of foliage in spruce and beech amounted to 35 and 70 kg/ha, respectively. Five years later (1987), these values increased to 770 and 360 kg/ha in spruce and beech, respectively. At a stand age of 21 years, foliage DM was determined to be 11,940 kg/ha for spruce and 3,050 kg/ha for beech. At the same time, the leaf-area index (LAI) was calculated to be 5.55 and 5.94 in spruce and beech, respectively. The method of foliage biomass quantification, based on the determination of foliage DM of mean sample trees and stand density, enabled to acquire complementary data usable in long-term research of the water regime of spruce and beech and simultaneously to provide information on the potential of biomass production and LAI value of both main commercial species in mountain forests of the Czech Republic.

Proximate composition, energy content, and fatty acid composition of marine species from Campbell Plateau, New Zealand

Campbell Plateau is an important fishing ground for the main commercial New Zealand species. Yet, studies on trophic interactions between species and their nutritional values are limited. The objectives of this study were to determine the proximate composition and energy contents of selected commercial and non‐commercial marine species from Campbell Plateau and their fatty acid (FA) composition, and to evaluate the degree to which species can be differentiated by their FA compositions. We analysed 43 fish specimens from 5 different species (Macruronus novaezelandiae, Lepidorhynchus denticulatus, Pseudophycis backus, Hemerocoetes spp. and Squalus acanthias), 17 cephalopod specimens from 2 species (Nototodarus sloani and Enteroctopus zealandicus), and 6 Metanephrops challengeri (crustacean). The variation of energy contents between fish species was not significant, but their lipid and protein contents varied significantly. FA signatures distinguished the species analysed and, at a broader scale, the type of habitat. Within‐specie s variability was important for benthic species. In general, the diet inference from FA trophic markers was consistent with reported diets from stomach contents.