Perceptions of resource users and managers towards fisheries management options in Kenyan coral reefs

Abstract  The perceptions of Kenyan resource users and managers towards gear and area management were examined through face-to-face interviews to identify areas of agreement and disagreement and compare with compliance. Opinions were sought about gears that sustained fish catch, gears discouraged by the government and traditional leaders, and the benefits of area management were sought. There was good agreement among most groups and traditional leaders about the gears discouraged by government, with beach seines and spear guns the most commonly listed. This indicates good agreement between government and traditions, promoted by recent government legislation, but compliance was poor since nearly two-thirds of fishers used these recently prohibited gears. This was due, in part, to lesser agreement concerning gears that promote a sustainable fishery, with spear guns and beach seines scaled low, but moderately supported in this respect by those fishers that use these gears. These gears persist because of the lack of shared evidence about the yields and sustainability of the various gears and social and economic aspects, such as increased competitiveness and decreased costs of the gears. There is evidence that beach seines lower yields but this gear persists because it is more competitive and has lower costs to the user than the other gears. Spear guns also persist because young and poor fishermen, who cannot afford costs associated with other gears, use them. Government employees scaled the benefits of area, and particularly closed area, management, higher than fishers, which is an issue of conflict but, nonetheless, has good compliance because of the long history of closed area management. For both types of management, shared perceptions alone were insufficient to achieve high compliance, and active enabling and enforcement by managers is needed.     

A role for partially protected areas on coral reefs: maintaining fish diversity?

• 1. Completely banning fishing from coral reefs is now accepted to have significant benefits for marine biodiversity and in many cases, fisheries. However, the benefits of regulating fishing on coral reefs, by restricting the methods used, or the total amount of fishing, are less well understood, even though such regulations are much more likely to be supported by fishermen.
• 2. This study assesses whether banning illegal, destructive fishing methods and reducing the numbers of fishermen visiting from outside an area benefits a coral reef fishery, despite unregulated fishing by local fishermen using non‐destructive methods.
• 3. The abundance, biomass, mean length, and species richness of nine commercially important fish families are compared across ten independent patch reefs inside and outside the 470 km² Menai Bay Conservation Area in Zanzibar, Tanzania.
• 4. Even after taking into account the effect of differences in habitat and the distance between reefs, 61% (±19.7%) more fish species were found in regulated than unregulated reefs. Fish abundance, biomass, and length were not affected, suggesting that banning destructive fishing may improve biodiversity, but that further regulations may be required to improve fish stocks.Copyright © 2011 John Wiley & Sons, Ltd.

     

Migration of landlocked brown trout in two Scandinavian streams as revealed from trap data

Abstract –  Anthropogenic barriers that may interfere or prevent fish migration are commonly found in streams throughout the distribution of salmonids. Construction of fish passages in streams is a common solution to this problem. However, the goal with fish passages is often, at least in Scandinavia, to allow Atlantic salmon ( Salmo salar L.) and migratory brown trout ( S. trutta L.) to get access to spawning areas above these barriers. Hence, the fish passages may often only be open during the spawning migration of salmonids (late summer to autumn). We present data, on wild brown trout migration, from two trapping systems in two Scandinavian streams showing that intra- and interstream migrations are common throughout the summer and autumn. Moreover, differences in size were found between trap-caught trout and electrofished trout where trapped trout were generally larger than electrofished trout. We suggest that the current regime with fish passages only open parts of the year can have negative effects on populations by depriving trout from the possibility to perform migrations throughout the year.     

North–south contrasts in decadal scale variations in lower trophic-level ecosystems in the Japan Sea

Regional comparisons of interannual variations in springtime lower trophic-level ecosystems were made for northern subarctic regions, and for southern Tsushima Current regions of the Japan Sea, based on archival hydrographic and biological data sets collected from the mid-1960s to the early 1990s. Variations related to the Pacific Decadal Oscillation were detected for plankton biomass in both northern and southern regions, although there were regional differences with respect to mechanisms and timing. Springtime stratification increased after the late 1970s in the north, roughly coinciding with the northern Pacific regime shift in 1976/77. Stratification also increased due to warming in the south in the early 1980s, several years after the 1976/77 regime shift. Responding to the increase in stratification, springtime biomass of phytoplankton and zooplankton increased in the north and decreased in the south. Principal component analysis revealed that hydrographic conditions during spring, rather than winter, determined springtime phytoplankton biomass. In northern regions, spring phytoplankton production may be enhanced by increased light availability, due to mixed layer stabilization. In the south, where background nutrient concentration within the water column was low, increases in stratification were likely to limit nutrient supply to the surface layer, resulting in decreases in phytoplankton production. A positive relationship between phytoplankton and zooplankton biomass suggested bottom-up control of secondary production in northern regions. The nature of the links between phytoplankton and zooplankton production was not clear in southern regions, where hydrographic conditions during winter seemed to be responsible for variations in springtime secondary production.     

Ontogenetic diet profiles and size-dependent diet partitioning of ruffe Gymnocephalus cernuus, perch Perca fluviatilis and pumpkinseed Lepomis gibbosus in Lake Balaton

Abstract –  Life-long diet ontogeny and size-dependent intra- and interspecific diet partitioning of the native ruffe and perch and the introduced pumpkinseed, were studied in Lake Balaton. Estimated intraspecific diet overlap was high in ruffe, whereas in perch and pumpkinseed only the neighbouring size groups exhibited a high diet similarity. Interspecific diet overlap among size groups of the three species was moderate and ≥60% diet overlap occurred only in 13 size group pair variations out of the 429 analysed. The earliest developmental stages of the three species were planktivorous, whereas larger ruffe and some size groups of perch and pumpkinseed fed dominantly on chironomids. Adult perch and pumpkinseed consumed different littoral macroinvertebrates, while the largest perch were piscivorous. Although productivities of the two studied areas differ significantly, this had only little effect on the diet ontogeny and diet partitioning of the three species. Present results suggest that in Lake Balaton these three species effectively partition food resources throughout their life span.     

Decadal change in abundance of surface migratory myctophid fishes in the Kuroshio region from 1957 to 1994

Decadal change in abundance of surface migratory myctophid fishes was examined in the Kuroshio region of the western North Pacific for the 35 yr from 1957 to 1994 in relation to the Kuroshio regime shift, indicated by changes in its transport volume and sea surface temperature in the early 1970s. Each year, samples were collected from the 0‐ to 1‐m depth layer at night, from January to March, at 83 stations on average. Ten species belonging to five genera occurred. Juveniles [standard length (SL) ≤ 40 mm] and adults (SL > 40 mm) of each species were analysed. In juveniles, Myctophum asperum, M. nitidulum, Symbolophorus evermanni and Centrobranchus brevirostris accounted for 91.1% of the total catch (7419 individuals), while M. nitidulum contributed 82.4% of the total adult catch (494 individuals). The abundance of juvenile S. evermanni, C. brevirostris and M. nitidulum showed prominent peaks in 1971, together with adult M. nitidulum. These peaks corresponded to extraordinarily high zooplankton abundance in the Kuroshio region in 1971, suggesting high recruitment success and low adult mortality in surface migratory myctophids. Smaller changes in abundance in other years were species‐specific, and the fluctuation patterns were mainly explained by year‐to‐year fluctuations in the strength of the Kuroshio and the geographical distribution of each species, i.e. an increased Kuroshio flow volume resulted in an increase in tropical species and a decrease in temperate species, but no change in the pan‐Kuroshio species.     

南海“长笼”渔具调查分析

2004年7月中旬至8月底,笔者主要对海南省、广东省和广西壮族自治区沿海的渔具种类及其分布情况进行补充调查.调查采用现场测定、咨询和访问当地渔民与现场观摩相结合的方法,对每种渔具的渔具结构、作业渔船、作业方法、渔具历史和技术改进等内容进行调查研究[1-2].     

Dynamic Optimization of System Parameters For the Epicyclic Gear Drive with Internal Tooth

The epicyclic gear drive with internal tooth has been analysed,the formula has been also deduced for computing the inertial force and change of contact force,and the dynamic optimization of system parameters for the force of bearing has been carried,it has given a reliable proof to reduce the dynamic load and prolong the life of bearing of three ring type reducer.