Application of least median of squared orthogonal distance (LMD) and LMD-based reweighted least squares (RLS) methods on the stock-recruitment relationship

ＩＮＴＲＯＤＵＣＴＩＯＮＴｈｅｍｏｓｔｉｍｐｏｒｔａｎｔａｎｄｇｅｎｅｒａｌｌｙｍｏｓｔｄｉｆｆｉｃｕｌｔｐｒｏｂｌｅｍｉｎｂｉｏｌｏｇｉｃａｌａｓｓｅｓｓｍｅｎｔｏｆｆｉｓｈｅｒｉｅｓｉｓｐｒｏｂａｂｌｙｔｈｅｒｅｌａｔｉｏｎｓｈｉｐｂｅｔｗｅｅｎｓｔｏｃｋａｎｄｒｅｃｒｕｉｔｍｅｎｔ(Ｈｉｌｂｏｒｎｅｔａｌ.,1992).Ａｎａｌｙｓｉｓｏｆｓｔｏｃｋｒｅｃｒｕｉｔｍｅｎｔ(ＳＲ)ｄａｔａｉｓｍｏｓｔｏｆｔｅｎｄｏｎｅｂｙｆｉｔｔｉｎｇｖａｒｉｏｕｓｃｕｒｖｅｓｏｆＳＲｒｅｌａｔｉｏｎｓｈｉｐｔｏｔｈ…     

大兴安岭北部大白山高山林线动态与气候变化的关系

高山林线植被对气候变化十分敏感,已成为全球变化研究的热点.研究了大兴安岭北部大白山高山林线的树木生长和群落更新动态及其与气候变化、火干扰等因素的关系.结果表明,林线树木的生长对气候变化十分敏感,但其敏感性随着海拔的降低而减弱;在高海拔,林线树木的径向生长与上年生长季后期(8月)降水负相关,而与上年初秋(9月)温度正相关,这限制作用随着海拔的降低而逐渐消失;与此相反,低海拔树木生长与当年冬末春初(3月)的温度负相关,但随着海拔上升这种限制作用消失.分析结果还表明,本地区的群落更新主要受火干扰驱动,而与气候变化没有显著关系.不同树种在火灾后更新的时间存在差异,这种差异又因海拔的不同而异,反映出不同树种的更新策略及对环境变化适应能力的差异.大兴安岭北部的高山林线在树木生长对气候变化的敏感性、与气候因子的关系及群落更新动态等方面均与干旱区林线有明显的差异,这些差异与气候条件、树种、更新驱动力等方面的不同有密切的关系.     

The biology,ecology and history of toheroa (Paphies ventricosa): a review of scientific,local and customary knowledge

Toheroa (Paphies ventricosa) were formerly abundant on west and south-facing New Zealand surf beaches. Harvesting of this surf clam was intense during the early to mid-1900s, and populations declined to levels where harvesting was no longer viable. Despite having now been protected for 35–45 years, toheroa have failed to recover. This paper reviews the history of human interactions with toheroa and our understanding of their ecology, with a view to identifying knowledge requirements for management and restoration. Historical and legal documents pertaining to the use of marine resources are reviewed and scientific understanding compared with customary and local knowledge. We consider the factors that may be preventing toheroa recovery and make recommendations for research into life history, habitat requirements and the ecological consequences of changing land use. Management options are suggested to address the effects of vehicle use on beaches, poaching and the failings of the customary harvest system.     

Intra-annual recruitment events of a shelf species around an island system in the NW Mediterranean

Seasonal pattern of fish recruitment can vary over years, and the coupling of such pattern with favourable trophic-environmental conditions may trigger non-stationary and non-linear effects on the yearly recruitment variability. The relative contribution of intra-annual discrete recruitment events (REs) to recruitment is often the basis of the inter-annual fluctuations in abundance and biomass of exploited fish populations which are based on a small number of age classes. In this study, REs of European hake (Merluccius merluccius L.) were identified in the north and south of the Balearic Islands (NW Mediterranean) during the 2004 recruitment season and investigated for growth and physiological and morphological condition. Five REs were identified with different contributions in abundance to the annual recruitment in each area coming from different intra-annual spawning batches. Growth rates were similar between the REs with the exception of the last event of the season. Conversely, large differences in morphological and physiological condition were observed between REs and were due to: different environmental-trophic scenarios encountered, and ontogenetic changes related to the recruitment to the shelf-break grounds (ca. 11 cm, 5–6 months of life) which triggered a trade-off in the energy allocation strategy. The spatial-temporal variability in the physiological condition among REs at the beginning of the recruitment season might be explained in the basis on a ‘condition expanded match–mismatch hypothesis’. We advance that individuals recruiting in the north, which were in better condition and temporally and spatially differenced from the south, have most probably hatched in separated locations with different food availability for larvae and early life stages. We propose that hake recruiting to the north and south of the island are from different origins, mainland and the islands respectively, and have benefited from different environmental conditions. This results in a different condition but not in different growth rates.     

Swimming abilities of wild-caught,late-stage larvae of Diplodus capensis and Sarpa salpa (Pisces: Sparidae) from temperate South Africa

Understanding the movement of marine fish larvae in coastal habitats requires an assessment of active swimming abilities. The critical speed (U-crit) and endurance swimming of late-stage larvae of Diplodus capensis and Sarpa salpa (Family Sparidae), common inshore recreational linefish species, were measured in a laboratory swimming chamber. Postflexion and settlement-stage larvae were collected from the wild in a small bay on the warm temperate coast of South Africa. Larvae were allowed to acclimate in captivity and were tested soon after capture. For the endurance tests a speed of 18 cm s⁻¹ was selected, as this approximated the mean current speed observed in the coastal environment of the area. The mean U-crit value (maximum swimming speed) for D. capensis (19 cm s⁻¹) was similar to that of S. salpa (18 cm s⁻¹), and similarly mean endurance (km swum) for S. salpa (8 km) was similar to that of D. capensis (6 km). The increase in critical speed and endurance swimming abilities with standard length was best described by a linear relationship. At lengths between 12 and 15 mm BL, D. capensis was the better swimmer, whereas S. salpa was the better swimmer between 15 and 16 mm BL. Of all the larvae that swam at critical speed, 90% were in an inertial environment. These swimming speeds exceed the modal current velocities observed in the shallow nearshore of the study region where these larvae occur abundantly. These swimming abilities provide larvae with the potential to influence their dispersal trajectories and ultimately influence their distribution in their nearshore nursery areas.     

Ecological and biological strategies of Etropus crossotus and Citharichthys spilopterus (Pleuronectiformes:Paralichthyidae) related to the estuarine plume, Southern Gulf of Mexico

Differences in the biological and ecological strategies of two tropical flatfishes, Etropus crossotus (fringed flounder) and Citharichthys spilopterus (bay whiff) are discussed. The comparative analysis was based on the seasonal distribution of relative abundance of the two species and flatfish movements utilizing estuarine plume influenced areas as part of their life cycles. Growth parameters of the von Bertalanffy equation and recruitment were estimated (FISAT software) to compare life cycle patterns. The recruitment patterns illustrate the key difference between “estuarine-dependent” and “estuarine-related” nekton strategies. Both species have a short life cycle with a continuous recruitment activity. E. crossotus is an estuarine-related species, with two recruitment pulses (winter frontal season), in the estuarine plume on the shelf. C. spilopterus is an estuarine-dependent species, with a main recruitment pulse during the rainy season in the estuarine plume, and a residual secondary pulse inside the adjacent estuarine system (Terminos Lagoon). The results show that the ecological success of these tropical coastal marine flatfish, with similar biological patterns, is based upon the sequential use (in time and space) of estuarine plume influenced habitats, suggesting that fish migration to shallow waters is related to food availability changes as a strategy towards optimum recruitment.     

基于个体的东海鲐鱼补充量年际变动模拟研究

东海鲐鱼（Scomber japonicus）是我国近海重要经济鱼种,年际资源量波动较大,物理环境对其资源量的丰歉影响很大。本文运用基于个体的东海鲐鱼生长初期生态模型,模拟1978-2013年东海鲐鱼资源补充量。模拟发现,物理环境的变化确实能导致东海鲐鱼资源补充量的年际差异,并且在90年代后出现了较大的波动,资源补充量最多的2002年（1.8×109尾）与最少的1996年（6.5×108尾）相差1.15×109尾。产卵后的15~30 d,即4月份鱼卵仔鱼所处的海洋物理环境对东海鲐鱼最终的资源补充量起到重要作用,4月底鱼卵仔鱼的存活量基本上决定了东海鲐鱼最终的资源补充量的多寡。4月份的水温是影响鲐鱼资源补充量的物理因素之一,4月份水温高有利于提高鲐鱼的资源补充量,相反,水温偏低不利于鲐鱼的资源补充量。4月份的台湾暖流的流速也是影响鲐鱼资源补充量的另外一个物理因素,4月份台湾暖流的势力强对东海鲐鱼最终资源补充量是有利的,相反,流速小对补充量较不利。4月份台湾暖流的水温、流速决定最终东海鲐鱼资源补充量。