海洋环境因子对澳洲鲐亲体补充量关系的影响——基于贝叶斯模型平均法的研究

澳洲鲐（Scomber australasicus）是西北太平洋重要的中上层经济鱼类,生命周期相对较短,资源量受补充量影响明显,了解澳洲鲐太平洋群系补充量状况对掌握其资源量及确保其可持续利用具有重要的意义。本文利用产卵场1（30°~32°N,130°~132°E）海表面温度（sea surface temperature,SST1）、产卵场2（34°~35°N,138°~141°E）海表面温度（SST2）、索饵场（35°~45°N,140°~160°E）海表面温度（SST3）、潮位差（tidal range,TR）、太平洋年代际涛动（Pacific decadal oscillation,PDO）和亲体量（spawning stock biomass,SSB）6个影响因子任意组合与补充量构建多个模型,运用贝叶斯模型平均法（Bayesian model averaging,BMA）分析各个环境因子对资源补充量的解释能力,并预测其补充量的变化。结果表明,SSB对补充量具有最长期且稳定的解释能力,其次是SST3,PDO、TR、SST2、SST1也对补充量模型具有一定的解释能力。SST3是环境因子中影响最大的因子,可能是由于补充群体在索饵场内生活时间较长,索饵场温度对仔鱼或鱼卵的生长存活有较大的影响。研究认为,基于BMA的组合预报综合考虑了各个模型的优势,优于单一模型,可用于澳洲鲐资源补充量的预测。     

Migration dynamics of Pacific herring (Clupea pallasii) and response to spring environmental variability in the southeastern Bering Sea

In the southeastern Bering Sea, Pacific herring (Clupea pallasii) migrate from the Pribilof Islands region where they overwinter, to the Alaska coast where they spawn in spring. The migration sustains a nearshore commercial fishery that targets roe-bearing females just prior to spawning. Herring also are taken as bycatch in groundfish trawl fisheries, where time and area closures in these fisheries are triggered by herring bycatch caps. Using herring bycatch data collected since the 1970s by National Marine Fisheries Service (NMFS) observers aboard groundfish fishing vessels, a retrospective analysis was conducted to describe the seasonal migration pattern of Pacific herring in the southeastern Bering Sea and to study its spatial and temporal variability. Observed changes in herring catch per unit of effort were compared with variability in climate and oceanographic conditions. The seasonal migration is complex, but annual shifts in migration routes and a possible northward shift of the overwintering grounds was identified. Pre-spawning herring aggregated in different areas depending on whether spawning occurred early or late in spring. The thermal structure of the ocean around the ice edge appears to influence herring migration timing and route as well as spawning date. Thus, on the basis of recent changes in sea-ice extent and duration, we suggest that the herring bycatch savings area that was developed from data collected in the 1980s should be revised to reflect prevailing conditions.     

黄海南部小黄鱼洄游分布及种群结构特征

Monthly fishery survey data of the small yellow croaker Larimichthys polyactis in the southern Yellow Sea from2003 and 2013 were employed to evaluate the variation in the resource distribution and biological characteristics(especially body length and sex ratio) in the population on a decadal scale.The results indicated that the small yellow croaker migrated from the Shawai fishing ground to the Dasha fishing ground in spring and was mainly distributed in the central and western parts of the Dasha fishing ground in April and May.Larimichthys polyactis in the Dasha fishing ground migrated eastward to offshore wintering grounds in autumn and reached the central Dasha fishing ground in October and November.The small yellow croaker entered the western waters of the Shawai fishing ground in winter.A large number of age 0+ fish occurred in the Shawai and Jiangwai fishing grounds in October of 2003 and 2013.The body lengths of the spawning stock and wintering stock in 2013 were larger than those in 2003,and the monthly sex ratios(female to male) were significantly less than 1 in both years.The monthly distribution of this fish in the southern Yellow Sea was consistent with a previous finding that "the stock migrated between the wintering grounds in the west of Jeju Island and the Lüsi spawning grounds" but tended to move more northward,with the spawning grounds extending outward.In the past decade,body length variation experienced a decline after an increase,rather than a steady decrease.The sex ratio in the single-stick stow net showed a tendency to increase over the decade,but was either less than or more than 1 depending on the fishing gear;therefore,further studies should be conducted to determine the sex structure.     

Neoliberal and neo-communal herring fisheries in Southeast Alaska: Reframing sustainability in marine ecosystems

The transformation of Pacific herring (Clupea pallasii) fisheries from communal to commons to neoliberal regulation has had significant impacts on the health and sustainability of marine ecosystems on the Northwest Coast of North America. Due to their abundance, seasonality, and sensitivity in disturbance, herring were carefully cultivated and protected by coastal Tlingit, Haida, and Tsimshian communities. The early industrial fishing era undermined this communalist approach in favor of an unregulated commons for bait and reduction fisheries, attracting non-local fleets and leading to conflicts with local Natives and tragedy of the commons style overexploitation of herring stocks by the mid-twentieth century. Since the 1970s, a re-regulated neoliberal sac roe fishery for Japanese markets has provided new opportunities for limited commercial permit holders, but with further depredations on local spawning populations. This paper uses frame theory and historical and political ecology to show how this transformation was justified by three critical but dubious (re)framings of Southeast herring populations under modern scientific management: (1) a reductionist framing of single species productivity models, expressed as herring “biomass,” within space and time (baseline scale framing); (2) the selective framing and privileging of human industrial predation under maximum sustainable yield (MSY) within a dynamic ecosystem of multiple predator populations (actor relations framing); and (3) the strategic framing of spawning failure events and policy responses to those events by professional fisheries managers (event–response framing). Finally, the paper argues for a new social–ecological systems approach, based on aboriginal models of herring cultivation, to sustain a commercial, subsistence, and restoration economy for the fishery.     

小黄鱼Larimichthys polyactis体长-体重关系幂指数与产卵群体空间分布相关性研究

鱼类产卵群体的相关研究一直是渔业领域关注的热点,对鱼类的产卵期、产卵场的研究是鱼类生态习性研究方向的重要组成部分。本文在前期研究证实鱼类体长-体重关系幂指数可以指示鱼类产卵期的基础上,利用2004年4个季节的东海大面积调查数据,尝试利用同一时间点上的各个调查点幂指数信息来分析鱼类产卵场分布特征,结果发现,成熟产卵个体仅在春季出现,而未成熟产卵个体4季均有分布,以此推测小黄鱼存在"跳过产卵"现象。另外发现,单靠幂指数大小,不能区分各个产卵成熟阶段,也不能区分产卵个体与非产卵个体;而怀卵个体出现站点的幂指数平均值偏低于匀速生长,空间上也具有类似特征,即幂指数相对低的地方一般对应怀卵个体相对集中的水域。本文依据幂指数分布,推断小黄鱼成熟产卵群体有3块相对集中水域,即舟山渔场近海、济州岛西南侧和江外与舟外渔场临近水域。     

Impact of climate and hydrology on juvenile fish recruitment towards estuarine nursery grounds in the context of climate change

Larvae of various coastal fish undergo immigration from spawning grounds towards estuarine nurseries. Several environmental factors can have an important impact on survival at this stage making it crucial for recruitment. Generalized linear models were applied in order to investigate the relation between river drainage, sea surface temperature (SST), NAO index and the North-South wind component intensity, over the two months prior to the estuarine colonization peak, and the densities of Platichthys flesus, Dicentrarchus labrax, Diplodus vulgaris and Diplodus bellottii in the nursery grounds based on a discontinuous historical dataset (from 1978 to 2006), for the Tagus estuary. The relation between SST over the 12 months prior to the estuarine colonization peak and fish densities in the nurseries was also investigated, as it integrates the periods of spawning stock maturation, spawning and larval immigration. While SST over the prior 12 months was negatively correlated with the abundance of P. flesus, it was positively correlated with the abundance of D. bellottii. Abundance of D. vulgaris was positively correlated with SST in the two months prior to the estuarine colonization peak, while the abundance of D. labrax was positively correlated with river drainage. The relations between SST and the abundance of P. flesus, a cold-water species with declining densities, and the subtropical species D. bellottii and D. vulgaris, which are increasing in abundance, are indicative of species abundance alterations related to climate warming. Dicentrarchus labrax will probably also be affected by climate change because of lowered precipitation and consequently river drainage.     

Analyses of egg size,otolith shape,and growth revealed two components of small yellow croaker in Haizhou Bay spawning stock

The geographical variations in life history characteristics of small yellow croaker Larimichthys polyactis, caused by experienced different environmental conditions, have been observed in China seas. Previous studies based on spatial distribution, migration route, and body morphometrics suggested a complex stock structure. In this study, to clarify the source of a spawning stock, we investigated the reproduction strategy and inter-structure of the Haizhou Bay (HZB) spawning stock in the middle Yellow Sea from both egg survey and adult otolith increment analysis. Egg and adult samples were collected from three surveys during spawning season in 2013. Distinct spatial and temporal variations were detected in egg distribution and size, and otolith shape analysis of adult fishes revealed two morphotypes with different increment growth using random forest cluster. The results indicate the existence of two components within the same spawning stock in HZB from different wintering grounds, and accordingly special protection should be required for this stock given the significance to maintain connectivity between adjacent subpopulations.     

Habitat mapping of the Atlantic bluefin tuna derived from satellite data: Its potential as a tool for the sustainable management of pelagic fisheries

The feeding and spawning habitats of the overfished Atlantic bluefin tuna (BFT) are mapped in the Mediterranean Sea and used in the present proposal for selecting restricted fishing grounds. The feeding habitat is mainly traced by oceanic fronts of satellite-derived temperature and chlorophyll while the spawning habitat is mostly characterized by an important heating of surface waters. The proposal recommends opening the fishery in feeding areas in case the BFT stock is low (current situation). Only spawning areas at its latest stage could be opened once the stock has recovered to its optimum yield. Due to the possible concentration of fishing vessels if fishing areas are restricted (e.g. four-fold increase with a 1/16th restriction of the Mediterranean Sea) the inspection activities could be better targeted. Identified spawning grounds, opened or closed to fishing, could also be particularly monitored by control operations. Within the authorized areas, the habitat maps would guide fishermen to the favourable habitat reducing their costs. The habitat guided management could be able to adapt the spatial and temporal distribution of the effort to the requirements of both the fisheries’ control and the resource. Its implementation is likely to protect the stock (a) by apparently decreasing illegal fishing which accounts in the recent years for more than 1/3rd of total catches, (b) by protecting the spawners to ensure a suitable recruitment and (c) by distributing the effort to respect the population structure. The first species studied is the emblematic bluefin tuna which is at high risk of collapse due to overfishing. The approach is a priori transposable to other epipelagic species of commercial importance.     

ESTIMATION OF FISHING MORTALITY AND ABUNDANCE OF PACIFIC HERRING IN THE HUANGHAI SEA BY COHORT ANALYSIS (VPA)

In this paper Cohort Analysis (VPA) with the data on catch in number by age and year is used to estimate independently fishing mortality, abundance and actual number of spawning stock of the Pacific herring in the Huanghai Sea. The results show that catch rate of the fishery is very high, and that the fishing mortality of the dominant age group aged 2-4 was 0.87-2.97 during the years 1971-1984. The size of year class has been decreased since 1982 although the variability for this species in the Huanghai Sea is frequent. This results in reducing the recruitment of the fishery, the abundance and the actual number of spawning stock. Therefore, an urgent management measure should be considered.The magnitude of several sources of errors in Cohort Analysis (VPA) are examined, and the precision of the estimates is mainly dependent on an accurate natural mortality.     

Diet of red-throated divers Gavia stellata reflects the seasonal availability of Atlantic herring Clupea harengus in the southwestern Baltic Sea

Red-throated divers are piscivorous seabirds considered to be opportunistic feeders. The overall knowledge about their diet at sea is scarce. A large sample size of 82 by-caught red-throated divers from two winter (2001–02 and 2002–03) and three spring periods (2003, 2004 and 2005) offered the unique opportunity to analyse their dietary composition in the Pomeranian Bight. This area represents a hot spot in their winter distribution in the southwestern Baltic Sea and a marine protected area has been established due to its importance for the divers and other seabird species. Diet composition was analysed based on stomach and gut contents. The comparison of the different prey species was mainly based on reconstructed biomass using regressions between skeletal hard parts such as otoliths and original fish length and weight. The diet of the divers comprised eleven different fish species and nine different families. No interannual differences in the consumption of the nine most important prey species could be observed. However, in contrast to the other fish species the consumption of Atlantic herring and zander differed significantly between seasons. Herring supplied the majority of prey biomass in all three spring periods and zander in both winter periods. Moreover, the average length of herring consumed differed significantly between seasons. In winter, smaller herring was consumed compared to spring. The distinct seasonal changes in the diet composition were paralleled and most probably evoked by the migration pattern of the Western Baltic spring spawning herring which has its main spawning grounds adjacent to the study area. Based on the habitat requirements of the different prey species it could be inferred that mostly the coastal waters of the bight were used for foraging. Its function as spawning, nursery area and feeding ground with numerous resident and migrating fish species available might explain the important role of the Pomeranian Bight as wintering and staging area for red-throated divers in the southwestern Baltic Sea.     

太平洋褶柔鱼冬生群资源丰度变动对ENSO事件的响应研究

太平洋褶柔鱼为大洋性经济鱼种,具有一年生命周期,其资源变动受气候和海洋环境条件的显著影响。本研究根据日本提供的2003-2012年太平洋褶柔鱼冬生群体的渔业统计数据,结合产卵场环境数据以及尼诺指数ONI（定义为Niño 3.4区海表温度距平值）,分析不同气候条件下（厄尔尼诺和拉尼娜）太平洋褶柔鱼冬生群体产卵场海表温度（SST）、叶绿素a（Chl-a）浓度以及适宜产卵面积（SSA）的变动情况及对其资源丰度（CPUE）的影响。结果表明,太平洋褶柔鱼冬生群体产卵场SST、Chl-a浓度和SSA具有明显的季节性变化。相关分析表明,各年CPUE与Chl-a浓度以及SSA具有显著的正相关关系（p<0.05）,但与SST相关性不显著（p>0.05）。此外,厄尔尼诺和拉尼娜事件通过驱动太平洋褶柔鱼冬生群体产卵场SSA和关键海域（25°-29°N,122.5°-130.5°E）内的Chl-a空间分布和大小变化,从而改变其资源丰度,但影响作用随各异常事件的强度不同而变化,具体表现为：发生弱强度厄尔尼诺事件时,产卵场SSA较高,Chl-a浓度处于较低水平,导致资源补充量处于较低水平,CPUE降低;发生中等强度厄尔尼诺事件时,产卵场SSA较低,但Chl-a浓度处于较高水平,导致资源补充量增加,CPUE处于上升水平;发生中等强度拉尼娜事件时,产卵场SSA和Chl-a浓度均处于较高水平,资源补充量显著增加,CPUE显著升高。研究表明,厄尔尼诺和拉尼娜事件对太平洋褶柔鱼冬生群体产卵场摄食孵化环境和资源丰度变动具有显著影响。     

Life cycle of chokka-squid Loligo reynaudii in South African waters

This short note summarises past and current knowledge of the life cycle of chokka-squid Loligo reynaudii d’Orbigny, 1845, in South African waters. Prior to approximately 2010, the chokka-squid stock was considered simple and uniform, with one paralarval pool, the drift of paralarvae westwards, one main nursery area and one main, long spawning migration of adult squid eastwards, back to the main spawning grounds. Based on new information, this life-history scheme has been revised. Genetically, the stock is uniform; however, morphologically, it comprises three main geographic groups. It is proposed that the differences between the groups originate from many different paralarval events and that short (not long) migrations dominate the life cycle.     

Spatial distribution of Illex argentinus in San Matias Gulf (Northern Patagonia,Argentina) in relation to environmental variables: A contribution to the new interpretation of the population structuring

Traditionally, it was assumed that major spawning activity of Illex argentinus occurs in discrete pulses along the outer-shelf/slope off Argentina/southern Brazil during late-fall/winter and that early life stages develop near the Brazil–Malvinas Confluence (BMC). However, a novel hypothesis of the population structuring of the species was proposed that states that coastal waters may be important as spawning and feeding grounds. Here, we analyzed the spatial distribution of Illex argentinus inside San Matias Gulf based on the position of the CPUE of jiggers in order to improve the knowledge of the population structuring in coastal regions. Squids were mainly concentrated on the northern region of the gulf where favorable oceanographic conditions (e.g. water stratification, chlorophyll-a concentration peaks) to feeding and spawning are present. These results provided empirical evidences that individuals of I. argentinus use Argentinean coastal waters, particularly San Matias Gulf, as permanent feeding and spawning grounds which supports the new hypothesis.     

Spawning characteristics of <Emphasis Type="Italic">Clupea pallasii</Emphasis> in the coastal waters off Gyeongnam,Korea, during spawning season

The purpose of this study is to research the characteristics of spawning grounds of Clupea pallasii found at 1 spawning ground located in the coast of Yeongun-ri, Tongyeong, Gyeongnam, and 3 stations in Jinhae Bay. Diving observation was performed from January to June, 2014 at the coast of Yeongun-ri, and from February to June, 2016 at Jinhae Bay after total 4 stations (A: Gusan-myeon, B: Haengamdong, C: Hacheong-myeon, D: Jam-do) were constituted. During observation period, 1 spawning ground was found in Tongyeong area in January. In Jinhae Bay spawning grounds were found at 3 stations (A, B, D) out of 4 stations in February. Regarding the surrounding environment of spawning ground found at Yeongunri, Tongyeong, various kinds of seaweeds were distributed up to 1–5 m depth, and many branch type red algae were distributed. In case of Jinhae Bay, seaweeds were widely distributed from shallow water to 5 m depth. In addition, the scope that eggs were attached was considerably wide compared to Tongyeong area, and they were found at all the 3 spots, so C. pallasii is thought to use Jinhae Bay for its spawning ground widely. Eggs were attached from the surface to 3–4 m, and like Tongyeong area, eggs were attached to mostly branch type of red algae. The results of this study suggest that the spawning season of the C. pallasii in coast waters off Gyeongnam is until mid-February.     

Environmental drivers of small scale spatial variation in the reproductive schedule of a commercially important bivalve mollusc

Understanding variability in reproductive schedules is essential to the management of recruitment limited fisheries such as that of Pecten maximus. Small scale (<5 km) variation in gonad condition and the onset of spawning of P. maximus were found among commercial scallop grounds in Isle of Man waters. Environmental and fishing drivers of these spatial patterns were investigated using a generalised additive model. Rate of change in temperature over the month prior to sampling was identified as the short term driver of gonad weight associated with the autumn spawning event. Long term drivers were average annual chlorophyll a concentration, scallop density, stratification index and shell size. The model explained 42.8% of deviance in gonad weight. Within site variation in gonad condition was high, indicating a “bet hedging” reproductive strategy which may decrease the chance of fertilisation especially at low densities. Therefore, areas protected from fishing, where scallop densities can increase may help buffer against reproductive failure. An increase in shell length from 100 mm to 110 mm equated to an increase of approximately 20% in gonad weight. Protecting scallops from fishing mortality until 110 mm (age four) compared to 100 mm (age three) may lead to an overall increase in lifetime reproductive output by a factor of 3.4.     

Distribution patterns,stock size and life-history strategies of Cape horse mackerel Trachurus trachurus capensis,based on bottom trawl and acoustic surveys

Research surveys of Cape horse mackerel Trachurus trachurus capensis abundance on the south coast of South Africa are complicated because changes in the species' vertical and horizontal distribution limit the value of stock assessments based a single survey method. Annual bottom trawl surveys conducted in spring provide estimates of the abundance of fish close to the bottom over trawlable grounds. Between 1991 and 1994, hydroacoustic surveys conducted in spring have been used to estimate the pelagic portion of the stock, as well as the portion over untrawlable grounds. These two research datasets, as well as data from purse-seine, mid water and bottom trawl commercial landings, are reviewed to elucidate distribution patterns of horse mackerel and their migratory and spawning strategies. The problems and advantages of bottom trawl and acoustic surveys are discussed in the context of fluctuations in estimates of the size of the stock between 1991 and 1994 and the prevailing environmental conditions. It is concluded that combined acoustic and bottom trawl surveys are the only effective means of surveying horse mackerel, and that effort should be concentrated east of 22°E to assess the spawner stock. It is suggested that research effort directed at improving understanding of exchanges between West Coast (including Namibia) and South Coast population of horse mackerel, as well as of the role of vertical migrations in modulating these exchanges, would be beneficial.     

Climate change and the migratory pattern for Norwegian spring-spawning herring—implications for management

Norwegian spring-spawning herring (Clupea harengus) is a migratory fish stock, and the migratory pattern has changed several times. There seems to be a connection between altering climatic conditions and the size of fish, year-class strength and the migratory pattern. The changing juridical status of the herring has caused problems and conflicts between the parties involved in the fishery. Investigating whether the change is due to over fishing or to environmental causes, or a combination of both, was one of the objectives of the analysis. Furthermore, we have looked at the processes involved in finding solutions to the problem of managing straddling stocks.     

基于产卵场和索饵场适宜性的西北太平洋柔鱼丰度预测

柔鱼(Ommastrephes bartramii)是北太平洋重要的经济头足类。短生命周期的特征使其资源丰度主要取决于补充量,早期生活史阶段的海洋环境将直接影响补充量大小。利用2004-2015年我国鱿钓船队在西北太平洋的生产统计数据,以及产卵场和索饵场海表水温,将产卵场和索饵场等分成不同数量的海区,运用相关性分析和随机森林模型,筛选出产卵期各月产卵场最适海表水温范围占总面积的比值(Ps)和索饵期各月索饵场最适海表水温范围占总面积的比值(Pf)与单位捕捞努力量渔获量(CPUE)显著相关的海区,将Ps值或Pf值作为神经网络模型的输入变量,分别构建基于产卵场、索饵场的资源丰度预报模型,分析模型的优劣与预报准确度。结果表明:产卵场划分方案为5°×5°,索饵场为2.5°(经)×4°(纬)较为合适。随机森林筛选出的海区与相关性分析筛选出的适宜海区范围大致吻合,且随机森林能够识别与CPUE相关的潜在海域。模型的预报结果表明,其预报准确度均达到90%以上,随机森林筛选出的海区的最适海表水温范围占该海区的比值作为神经网络模型输入因子构建的模型优于相关性分析,预报准确度更高。基于产卵场海域构建的模型相对...     

Do bigger fish arrive and spawn at the spawning grounds before smaller fish: Cod (Gadus morhua) predation on beach spawning capelin (Mallotus villosus) from coastal Newfoundland

A relationship between body size and time of spawning has often been described for both pelagic and non-pelagic fish species that migrate for the purpose of spawning. The present study investigates this relationship for capelin (Mallotus villosus), a pelagic smelt-like species that spawns on the beaches of Newfoundland. Simple linear regressions were carried out separately for three groups of capelin: ovid females, spent females and males in three successive years (1982–1984). Bigger fish arrived near the spawning grounds first, for all three groups in all three years and was most obvious for female capelin. Analyses of stomach contents of Atlantic cod (Gadus morhua), an important predator of capelin in the Newfoundland area, showed a similar decrease in mean size of capelin throughout the capelin spawning season in June, July and August. Furthermore, analyses strongly suggest that early in the spawning seasons, when capelin abundance was high, cod selected for bigger capelin, whereas towards the end of the spawning seasons, when capelin abundance was low, cod did not show any size preference.     

Life histories of large,grazing copepods in a subarctic ocean gyre: Neocalanus plumchrus,Neocalanus cristatus, and Eucalanus bungii in the Northeast Pacific

Life histories for the dominant, larger copepods of the subartic Pacific have been constructed by sampling from weatherships patrolling Ocean Station P (50°N, 145°W) during 1980 and 1981. Neocalanus plumchrus reproduced at depths below 250 m from July through February. Copepodite stages were present in surface layers from October through August with a large peak in numbers and biomass in spring. Fifth copepodites prepared for diapuse in 38 days during spring and descended to depths below 250 m. They commenced immediately to mature, and the females reproduced without renewed feeding. This schedule contrasts with that of the population in the Strait of Georgia, which remains in diapause from July to January and matures exclusively in January and February. There appears to be a difference between the coastal and oceanic habitats in preparing the diapausing individuals for maturation.Maturation of the diapausing stock of N. plumchrus maintained constant adult populations, averaging 714 males m^?2 from June through October and 1,434 females m^?2 from August through January. This constancy, together with the exponential pattern of decline in the diapause stock from September through February, suggests that density of adults may regulate maturation of fifth copepodites. Offspring of individuals delaying maturation and, thus, reproduction would benefit from the resulting moderation of intraspecific competition, probably that among copepodites.Reproduction of Neocalanus cristatus also occurred below 250 m, and, while spawning was continuous through the year, there was a substantial peak in November. That resulted in a peak of abundance for early copepodite stages in mid-winter, and a peak for the fifth copepodite stage in June. Stocking of the population of fifth copepodites in diapause below 250 m occurred from July through October. Some fifth copepodites were present in surface layers through the entire summer, and some younger copepodites persisted through the summer in progressively declining abundance just below the mixed layer. In autumn 1980 resurgence of early copepodite populations was rapid, occurring during the course of a prolonged October storm. The storm may have improved the habitat either by cooling the mixed layer or by resupplying nutrients to the euphotic zone.Eucalanus bungii reproduced in the mixed layer in early May and in early July. The first event was a spawning by females that had previously spawned in 1979 and then had returned to diapause. The second, heavier spawning (more females, more eggs per female) was by newly matured females from stocks that had overwintered as fifth copepodites. Nauplii peaked sharply in abundance on 19 July, one week after the peak in spawning. First and second copepodites peaked on 1 August, and all had advanced to the third copepodite stage by September. The diapause stock was established by September, principally between 250 and 500 m, and consisted of copepodite stages from third to sixth. Duration of the E. bungii life cycle appears to be typically two years. New nauplii develop as far as the third or fourth copepodite stage during their first summer, then enter diapause. The second summer they advance to the fifth copepodite stage and reenter diapause. Fifth copepodites mature in their third summer at two years of age. The males remain at depth and mate without subsequent feeding. Females migrate at night to the mixed layer where spawning occurs. About 20% of females that had already spawned in 1980 reentered diapause. They would reproduce again in their fourth summer at three years of age. All aspects of the life cycle suggest low mortality rates for copepodite stages, particularly at depth in the habitat occupied during diapuse. There can be no premium on rapid reproduction for E. bungii in the subartic Pacific, and there must even be benefit from spreading reproduction between years. This iteroparity may amount to a “bet-hedging” tactic, the young from a given mother having more than one chance to find sustaining conditions. It also produces gene flow between the year classes of the biennial life cycle.