Respiration (= oxygen consumption) rates and electron transport system (ETS) enzyme activities in conjunction with body carbon and nitrogen composition (for respiration) or protein (for ETS) were determined for over 50 copepod species from the mesopelagic (M; 500 to 1000 m), upperbathypelagic (UB; 1000 to 2000 m) and lower-bathypelagic (LB; 2000 to 3000 m) zones of the western subarctic Pacific. Calculated specific respiration rates (SR, a fraction of body carbon respired) at in situ temperatures (3, 2 and 1.5°C for the M, UB and LB zones, respectively) were greater for the M zone copepods (mean: 1.1% body C d ). Respiration rates adjusted to those at 1°C by using a Q 10 value (2.0), and to those of specimens with 1 mg body nitrogen by using a body mass exponent ( 0.8) , showed the same depth-related decline from the M zone to the LB zone. Stepwise regression analysis revealed that stage/sex, feeding type and/or reaction speeds (as judged by the presence/absence of myelin sheath enveloping axons) of copepods were possible additional variables affecting their respiration rates and ETS activities. The reduction in respiration rates and ETS activities from the M zone to the UB or LB zone is more pronounced when respiration rate data on Arctic/Antarctic epipelagic copepods is added; the same is true for ETS activities when respiration rate data is added from copepods dominant in the subarctic Pacific. The present results are compared with those of micronektonic crustaceans and fishes reported for specimens collected from 500 to 2000 m in other regions and discussed in the light of the 'visual interactions' hypothesis. KEY WORDS: Mesopelagic · Bathypelagic · Copepods · Respiration · ETS activity · Western North PacificResale or republication not permitted without written consent of the publisher

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Lake Victoria is one of the African Great Lakes, and an important source of affordable protein food in the form of fish. It provides employment, income, and export earnings to the riparian communities. Despite this importance there are major concerns about the status and exploitation of the fisheries. This study assesses if current extraction rates/yield of Nile perch, Lates niloticus (L.), from Lake Victoria are sustainable for the foreseeable future. The paper reviews trends in catch and effort in the Nile perch fishery and models the expected scenarios using ECOPATH. The fishery exhibits, classic indicators of intensive fishing, erring towards overexploitation, including: (i) decline in total estimated catch of Nile perch in recent years from the peaks in the 1990s. This is coupled with a shift in contribution of catches from higher trophic level species (Nile perch) to lower trophic level (dagaa) species. (ii) Three major trends in the fishing effort are evident: (a) almost doubling of the number of fishers and fishing boats between 1990 and 2000, and the even greater expansion between 2000 and 2002; (b) a large scale increase in the number of gears operational in the lake; and (c) the propensity for use of ÔillegalÕ gears. (iii) Catchper-unit-effort has declined from about 80 to 45 kg per boat day. (iv) Predictive modelling (ECOSIM) of the future of the Nile perch fisheries under a scenario of increased fishing effort suggests that the fisheries are unsustainable and will decline in the long term. It appears that the Nile perch stocks in the three riparian countries are under intense fishing pressure, and unless concerted action is taken, the potential for degradation of the resources is prevalent. In view of the importance of these fisheries, it is recommended that a precautionary approach to further intens-ification of the fisheries is adopted until such time empirical evidence shows that the fisheries are capable of further expansion and intensification. The main options for management are devolvement of responsibilities for the fisheries to the communities, enforcement of existing regulations, improved monitoring and data collection processes, reducing post-harvest losses and increasing the value of the products to the export market.

Differences in egg number and egg size within a wild population of white-spotted char (Salvelinus leucomaenis) were examined from the perspective of maternal growth history by using a back-calculation method. Relatively greater egg size variation occurred among females (61.6%) than within females (38.4%). Larger females produced a larger number of eggs, which were also larger in size. To understand the causes of variation in egg number and egg size, several contributory factors determining maternal size were considered (initial size, growth rate for each age, total age). Egg number was not associated with maternal growth history. Contrary to egg number, egg size was strongly associated with maternal growth history; high growth in the first year was negatively associated with egg size, but high growth in the second year was positively associated with egg size. The results indicated that white-spotted char potentially exhibit phenotypic plasticity in egg size according to their growth history.

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Harvest control rules (HCRs) for sustainable fishery management have been developed for data-limited fish species for which stock assessments cannot be conducted. However, HCRs have largely not considered mixed-species catches, as when fishing-effort data are widely pooled for numerous minor species in a multispecies fishery. Presently, a feedback HCR has been successfully applied in Japanese fisheries management. By combining management strategy evaluation with a simulation to generate mixed-species data from a multispecies fishery that assume constant catchability (q) among species, we evaluated the performance of this feedback HCR and then compared its performance using species-specific data. In most cases, the biomass was controlled over that needed for maximum sustainable yield (MSY), and the fishing effort was under the fishing mortality consistent with achieving MSY (FMSY). However, for slow-growing species, the biomass might become lower than what is required to remain capable of producing MSY, even though fishing effort was controlled under FMSY. The results show that the feedback HCR is appropriate for multispecies fisheries management where only mixed-species data are available but with special monitoring for slow-growing minor species.

Two types of Berardius are recognised by local whalers in Hokkaido, Japan. The first is the ordinary Baird’s beaked whale, B . bairdii , whereas the other is much smaller and entirely black. Previous molecular phylogenetic analyses revealed that the black type is one recognisable taxonomic unit within the Berardius clade but is distinct from the two known Berardius species. To determine the characteristics of the black type, we summarised external morphology and skull osteometric data obtained from four individuals, which included three individuals from Hokkaido and one additional individual from the United States National Museum of Natural History collection. The whales differed from all of their congeners by having the following unique characters: a substantially smaller body size of physically mature individuals, proportionately shorter beak, and darker body colour. Thus, we conclude that the whales are a third Berardius species.