Genetic stock identification of overwintering chum salmon in the North Pacific Ocean

Understanding stock and age-specific seasonal migrations of Pacific salmon during ocean residence is essential to both the conservation and management of this important resource. Based upon 11 microsatellites assayed on 265 individuals collected aboard international research surveys during winter 2009, we found substantial differences in the age-specific origin of chum salmon (Oncorhynchus keta) in the North Pacific Ocean. Overall, Asian stocks dominated the collections, however, ocean age 1 fish were primarily of Japanese origin and ocean age 2–3+ fish were predominantly of Russian origin. These results suggest that cohorts of chum salmon stocks migrate nonrandomly in the North Pacific Ocean and adjacent seas.     

Perspectives on wild and hatchery salmon interactions at sea,potential climate effects on Japanese chum salmon,and the need for sustainable salmon fishery management reform in Japan

Pacific salmon (Oncorhynchus spp.) play an important role as a keystone species and provider of ecosystem services in the North Pacific ecosystem. We review our studies on recent production trends, marine carrying capacity, climate effects and biological interactions between wild and hatchery origin populations of Pacific salmon in the open sea, with a particular focus on Japanese chum salmon (O. keta). Salmon catch data indicates that the abundance of Pacific salmon increased since the 1976/77 ocean regime shift. Chum and pink salmon (O. gorbuscha) maintained high abundances with a sharp increase in hatchery-released populations since the late 1980s. Since the 1990s, the biomass contribution of hatchery returns to the total catch amounts to 50% for chum salmon, more than 10% for pink salmon, and less than 10% for sockeye salmon (O. nerka). We show evidence of density-dependence of growth and survival at sea and how it might vary across spatial scales, and we provide some new information on foraging plasticity that may offer new insight into competitive interactions. The marine carrying capacity of these three species is synchronized with long-term patterns in climate change. At the present time, global warming has positively affected growth and survival of Hokkaido populations of chum salmon. In the future, however, global warming may decrease the marine carrying capacity and the area of suitable habitat for chum salmon in the North Pacific Ocean. We outline future challenges for salmon sustainable conservation management in Japan, and recommend fishery management reform to sustain the hatchery-supported salmon fishery while conserving natural spawning populations.     

International cooperation in salmon fisheries and a comparative law perspective on the salmon and ocean ranching industry

Abstract

The salmon industry has steadily developed during the last two decades, leading to an increasing awareness about the legal problems that need to be solved. Both production in ocean ranching and in captivity have prompted the enactment of important rules of international and domestic law. While international law has provided for a basic regulatory framework, embodied in the United Nations Convention on the Law of the Sea and a number of regional and bilateral treaties, domestic law has concentrated on the specific technical issues that relate to conservation, fishing rights, and organization of the industry generally.

The article discusses the aggregate of legal rules applicable to salmon production, including the comparative law perspective emerging from the national legislations of the main producers in the world. Various legal and economic models are identified and their incidence on the industry is examined in light of actual experiences. The rules of international law in the field are becoming consolidated, and domestic legislation is contributing new insights into the matter while, in addition, exercising a strong influence in the formation of customary law.     

On the Persistence of Stereotypes Concerning the Marine Ecology of Pacific Salmon (<Emphasis Type="Italic">Oncorhynchus</Emphasis> spp.)

Some of the views on the marine ecology of Pacific salmon (Oncorhynchus spp.) that were popular in the second half of the 20th century are discussed critically: the absolutization of the influence of sea surface temperature on distribution of salmon and strength of their year classes, as well as the conclusions on the shortage of food (particularly in winter) and the fierce competition for food, the “suppression” of other salmon species and own adjacent broodline by pink salmon, the limited carrying capacity of the pelagic zone of subarctic ocean waters for salmon, the distortion of the structure of epipelagic communities in ecosystems of the North Pacific due to the large-scale stock enhancement of chum salmon, etc. Most of these ideas have not been confirmed by the data of long-term monitoring conducted in the form of complex marine expeditions by the Pacific Research Fisheries Center (TINRO Center) in the Far-Eastern Seas and adjacent North Pacific waters since the 1980s. The data show that Pacific salmon are ecologically very flexible species with a wider temperature range of habitat than was previously believed. Salmon are able to make considerable vertical migrations, easily crossing zones of sharp temperature gradient and different water masses. Having the wide feeding spectra and being dispersed (as non-schooling fish) when feeding in the sea and ocean, they successfully satisfy their dietary needs in vast areas even with relatively low concentrations of prey organisms (macroplankton and small nekton). The total biomass of all the Pacific salmon species in the North Pacific is not greater than 4–5 million t (including 1.5–2.0 million t in Russian waters), whereas the biomass of other common species of nekton is a few hundreds of millions of tons. Salmon account for 1.0–5.0% of the total amount of food consumed by nekton in the epipelagic layer of the western Bering Sea, 0.5–1.0% in the Sea of Okhotsk, less than 1% in the ocean waters off the Kuril Islands, and 5.0–15.0% in the ocean waters off East Kamchatka. Thus, the role of Pacific salmon in the trophic webs of subarctic waters is rather moderate. Therefore, neither pink nor chum salmon can be considered as the species responsible for the large reorganization in ecosystems and the population fluctuations in other common nekton species.     

Annual changes in the population size of the salmon louse Lepeophtheirus salmonis (Copepoda: Caligidae) on high-seas Pacific Salmon (Oncorhynchus spp.), and relationship to host abundance

The population size of the salmon louse, Lepeophtheirus salmonis, was monitored annually in the summers of 1991–1997 by examining six species of Pacific salmon (Oncorhynchus spp.) caught by surface long-lines in oceanic offshore waters of the North Pacific Ocean and Bering Sea. The annual copepod population size on all salmonids caught was estimated by combining the calculated number of copepods carrying on each salmonid species. The copepod population fluctuated markedly from year to year, which resulted largely from marked annual changes in abundance of pink salmon (O. gorbuscha). Since pink salmon were most frequently and heavily infected and since their abundance changed every year, the copepod population was high in the years when this salmonid species was abundant, but low when it was rare. On the contrary, chum salmon (O. keta) did not show high prevalence and intensity of infection, but the annual abundance of this host species was consistently high, i.e. chum salmon carried many copepods every year. Copepods on other salmonid species (sockeye salmon O. nerka, coho salmon O. kisutch, chinook salmon O. tshawytscha, and steelhead trout O. mykiss) constantly formed a small percentage of the total copepod population. Both chum and pink salmon are the most important hosts in terms of their substantial contribution to support the copepod population, but the importance as hosts of each species is definitely different between the species. Chum salmon is a stable important host supporting the copepod population at a relatively high level every year, while the number of copepods on pink salmon annually exhibits marked fluctuations, and this salmonid species is regarded as an unstable important host.     

Eliminating driftnets from the North Pacific Ocean: U.S.—Japanese cooperation in the international North Pacific Fisheries Commission, 1953–1993

Japanese negotiators agreed to eliminate driftnet fishing for salmon in the North Pacific Ocean by the end of 1992. The Japanese high seas fishing fleet for salmon had been an economically valuable yet environmentally destructive operation for four decades. The Japanese government progressively phased out lucrative Japanese salmon fishing operations in the North Pacific, apparently capitulating to U.S. pressure. No U.S. enforcement with punitive sanctions proved necessary, however. Specific characteristics of the international market created the possibility of an environmentally benign international agreement. International integration of the market for fisheries products was made possible by the high market value of salmon in the United States and in Japan. In the 1970s, foreign direct investment from vertically integrated, Tokyo‐based fishing firms into canning and processing operations in Alaska and the Pacific Northwest facilitated U.S. Japanese agreement. The high existence (nonuse) value of marine mammals in the United States was also an important factor.     

MOLECULAR GENETIC EVIDENCE FOR PARALLEL LIFE-HISTORY EVOLUTION WITHIN A PACIFIC SALMON (SOCKEYE SALMON AND KOKANEE,ONCORHYNCHUS NERKA)

The Pacific salmon Oncorhynchus nerka typically occurs as a sea-run form (sockeye salmon) or may reside permanently in lakes (kokanee) thoughout its native North Pacific. We tested whether such geographically extensive ecotypic variation resulted from parallel evolutionary divergence thoughout the North Pacific or whether the two forms are monophyletic groups by examining allelic variation between sockeye salmon and kokanee at two minisatellite DNA repeat loci and in mitochondrial DNA (mtDNA) Bgl II restriction sites. Our examination of over 750 fish from 24 populations, ranging from Kamchatka to the Columbia River, identified two major genetic groups of North Pacific O. nerka: a “northwestern” group consisting of fish from Kamchatka, western Alaska, and northwestern British Columbia, and a “southern” group consisting of sockeye salmon and kokanee populations from the Fraser and Columbia River systems. Maximum-likelihood analysis accompanied by bootstrapping provided strong support for these two genetic groups of O. nerka; the populations did not cluster by migratory form, but genetic affinities were organized more strongly by geographic proximity. The two major genetic groups resolved in our study probably stem from historical isolation and dispersal of O. nerka from two major Wisconsinan glacial refugia in the North Pacific. There were significant minisatellite DNA allele frequency differences between sockeye salmon and kokanee populations from different parts of the same watershed, between populations spawning in different tributaries of the same lake, and also between sympatric populations spawning in the same stream at the same time. MtDNA Bgl II restriction site variation was significant between sockeye salmon and kokanee spawning in different parts of the same major watershed but not between forms spawning in closer degrees of reproductive sympatry. Patterns of genetic affinity and allele sharing suggested that kokanee have arisen from sea-run sockeye salmon several times independently in the North Pacific. We conclude that sockeye salmon and kokanee are para- and polyphyletic, respectively, and that the present geographic distribution of the ecotypes results from parallel evolutionary origins of kokanee from sockeye (divergences between them) thoughout the North Pacific.     

Evidence for competitive dominance of Pink salmon (<Emphasis Type="Italic">Oncorhynchus gorbuscha</Emphasis>) over other Salmonids in the North Pacific Ocean

Relatively little is known about fish species interactions in offshore areas of the world’s oceans because adequate experimental controls are typically unavailable in such vast areas. However, pink salmon (Oncorhynchus gorbuscha) are numerous and have an alternating-year pattern of abundance that provides a natural experimental control to test for interspecific competition in the North Pacific Ocean and Bering Sea. Since a number of studies have recently examined pink salmon interactions with other salmon, we reviewed them in an effort to describe patterns of interaction over broad regions of the ocean. Research consistently indicated that pink salmon significantly altered prey abundance of other salmon species (e.g., zooplankton, squid), leading to altered diet, reduced total prey consumption and growth, delayed maturation, and reduced survival, depending on species and locale. Reduced survival was observed in chum salmon (O. keta) and Chinook salmon (O. tshawytscha) originating from Puget Sound and in Bristol Bay sockeye salmon (O. nerka). Growth of pink salmon was not measurably affected by other salmon species, but their growth was sometimes inversely related to their own abundance. In all marine studies, pink salmon affected other species through exploitation of prey resources rather than interference. Interspecific competition was observed in nearshore and offshore waters of the North Pacific Ocean and Bering Sea, and one study documented competition between species originating from different continents. Climate change had variable effects on competition. In the North Pacific Ocean, competition was observed before and after the ocean regime shift in 1977 that significantly altered abundances of many marine species, whereas a study in the Pacific Northwest reported a shift from predation- to competition-based mortality in response to the 1982/1983 El Nino. Key traits of pink salmon that influenced competition with other salmonids included great abundance, high consumption rates and rapid growth, degree of diet overlap or consumption of lower trophic level prey, and early migration timing into the ocean. The consistent pattern of findings from multiple regions of the ocean provides evidence that interspecific competition can significantly influence salmon population dynamics and that pink salmon may be the dominant competitor among salmon in marine waters.     

The Dugong Action Plan for the South Pacific: An Evaluation Based on the Need for International and Regional Conservation of Sirenians

Abstract

The purpose of this article is to set out the essential requirements for a successful regional agreement for Sirenians in the South Pacific. To achieve this, the current Dugong Action Plan, which is being formed under the auspice of the South Pacific Regional Environmental Program, will be juxtaposed against the “best practice” in this area, as evinced by current development in international environmental law and policy relating to Sirenians.     

Population Dynamics of the Pink Salmon Oncorhynchus gorbuschain the Basin of the Sea of Okhotsk in the 1990s

In the 1990s, an extensive body of data was gathered on the size of the Oncorhynchus gorbuschapink salmon populations of the Sea of Okhotsk at all the main developmental stages. A significant increase in numbers was found for juvenile pink salmon migrating into the offshore regions of the Sea of Okhotsk and the Pacific waters around the Kurils: from 250–450 million in 1990–1991 to 807–1570 million fish in 1993–1999. The overall number of migrating pink salmon in even years sharply increased in 1994 up to 215 million fish. After 1994, this estimate exceeded the number of migrating pink salmon in preceding odd years. Ocean survival of juvenile pink salmon gradually declined. This may be related to changes in the North Pacific pelagic ecosystems.     

Effects of Salmon-Derived Nutrients and Habitat Characteristics on Population Densities of Stream-Resident Sculpins

Movement of nutrients across ecosystem boundaries can have important effects on food webs and population dynamics. An example from the North Pacific Rim is the connection between productive marine ecosystems and freshwaters driven by annual spawning migrations of Pacific salmon (Oncorhynchus spp). While a growing body of research has highlighted the importance of both pulsed nutrient subsidies and disturbance by spawning salmon, their effects on population densities of vertebrate consumers have rarely been tested, especially across streams spanning a wide range of natural variation in salmon densities and habitat characteristics. We studied resident freshwater prickly (Cottus asper), and coastrange sculpins (C. aleuticus) in coastal salmon spawning streams to test whether their population densities are affected by spawning densities of pink and chum salmon (O. gorbuscha and O. keta), as well as habitat characteristics. Coastrange sculpins occurred in the highest densities in streams with high densities of spawning pink and chum salmon. They also were more dense in streams with high pH, large watersheds, less area covered by pools, and lower gradients. In contrast, prickly sculpin densities were higher in streams with more large wood and pools, and less canopy cover, but their densities were not correlated with salmon. These results for coastrange sculpins provide evidence of a numerical population response by freshwater fish to increased availability of salmon subsidies in streams. These results demonstrate complex and context-dependent relationships between spawning Pacific salmon and coastal ecosystems and can inform an ecosystem-based approach to their management and conservation.     

Seasonal foraging movements and migratory patterns of female Lamna ditropis tagged in Prince William Sound, Alaska

Conventional and electronic tags were used to investigate social segregation, distribution, movements and migrations of salmon sharks Lamna ditropis in Prince William Sound, Alaska. Sixteen salmon sharks were tagged with satellite transmitters and 246 with conventional tags following capture, and were then released in Prince William Sound during summer 1999 to 2001. Most salmon sharks sexed during the study were female (95%), suggesting a high degree of sexual segregation in the region. Salmon sharks congregated at adult Pacific salmon Oncorhynchus spp. migration routes and in bays near Pacific salmon spawning grounds in Prince William Sound during July and August. Adult Pacific salmon were the principal prey in 51 salmon shark stomachs collected during summer months in Prince William Sound, but the fish appeared to be opportunistic predators and consumed sablefish Anoplopoma fimbria, gadids, Pacific herring Clupea pallasi, rockfish Sebastes spp. and squid (Teuthoidea) even when adult Pacific salmon were locally abundant. As Pacific salmon migrations declined in late summer, the salmon sharks dispersed; some continued to forage in Prince William Sound and the Gulf of Alaska into autumn and winter months, while others rapidly moved south‐east thousands of kilometres toward the west coasts of Canada and the U.S. Three movement modes are proposed to explain the movement patterns observed in the Gulf of Alaska and eastern North Pacific Ocean: ‘focal foraging’ movements, ‘foraging dispersals’ and ‘direct migrations’. Patterns of salmon shark movement are possibly explained by spatio‐temporal changes in prey quality and density, an energetic trade‐off between prey availability and water temperature, intra‐specific competition for food and reproductive success. Transmissions from the electronic tags also provided data on depth and water temperatures experienced by the salmon sharks. The fish ranged from the surface to a depth of 668 m, encountered water temperatures from 4·0 to 16·8° C and generally spent the most time above 40 m depth and between 6 and 14° C (60 and 73%, respectively).     

Evidence for competition at sea between Norton Sound chum salmon and Asian hatchery chum salmon

Increasing production of hatchery salmon over the past four decades has led to concerns about possible density-dependent effects on wild Pacific salmon populations in the North Pacific Ocean. The concern arises because salmon from distant regions overlap in the ocean, and wild salmon populations having low productivity may compete for food with abundant hatchery populations. We tested the hypothesis that adult length-at-age, age-at-maturation, productivity, and abundance of a Norton Sound, Alaska, chum salmon population were influenced by Asian hatchery chum salmon, which have become exceptionally abundant and surpassed the abundance of wild chum salmon in the North Pacific beginning in the early 1980s. We found that smaller adult length-at-age, delayed age-at-maturation, and reduced productivity and abundance of the Norton Sound salmon population were associated with greater production of Asian hatchery chum salmon since 1965. Modeling of the density-dependent relationship, while controlling for other influential variables, indicated that an increase in adult hatchery chum salmon abundance from 10 million to 80 million adult fish led to a 72% reduction in the abundance of the wild chum salmon population. These findings indicate that competition with hatchery chum salmon contributed to the low productivity and abundance of Norton Sound chum salmon, which includes several stocks that are classified as Stocks of Concern by the State of Alaska. This study provides new evidence indicating that large-scale hatchery production may influence body size, age-at-maturation, productivity and abundance of a distant wild salmon population.     

Migration of Pacific Rim Chum Salmon on the High Seas: Insights from Genetic Data

Wild stocks of chum salmon, Oncorhynchus keta, have experienced recent declines in some areas of their range. Also, the release of hatchery chum salmon has escalated to nearly three billion fish annually. The decline of wild stocks and the unknown effects of hatchery fish combined with the uncertainty of future production caused by global climate change have renewed interest in the migratory patterns of chum salmon on the high seas. We studied the composition of high-seas mixtures of maturing and immature individuals using baseline data for 20 allozyme loci from 356 populations from throughout the Pacific Rim. Composition estimates were made from three time series. Two of these time series were from important coastal migratory corridors: the Shumagin Islands south of the Alaska Peninsula and the east coast of the Kamchatka Peninsula. The third was from chum salmon captured incidentally in the Bering Sea trawl fishery for walleye pollock. We also analyzed geographically dispersed collections of chum salmon captured in the month of July. The time series show dynamic changes in stock composition. The Shumagin Island corridor was used primarily by Northwest Alaskan and Asian populations in June; by the end of July stocks from the Alaska Peninsula and southern North America dominated the composition. The composition along the Kamchatka coast changed dramatically from primarily Russian stocks in May to primarily Japanese stocks in August; the previously undocumented presence of stocks from the Alaska Peninsula and Gulf of Alaska was also demonstrated. Immature chum salmon from throughout the Pacific Rim, including large proportions of southern North American stocks, contributed to the Bering Sea bycatch during the months of September and October. The migration routes of North American stocks is far more widespread than previously observed, and the Bering Sea is an important rearing area for maturing and immature chum salmon from throughout the species' range.     

Phylogeography of a salmonid fish,masu salmon Oncorhynchus masou subspecies-complex,with disjunct distributions across the temperate northern Pacific

1. Climate oscillations during the Pleistocene had profound effects on the evolutionary history of freshwater fishes now distributed across northern temperate regions. The extent of continental glaciation on the western side of the North Pacific, including areas of East Asia, was more limited as compared with regions of North America, Europe and high-latitude areas of the North Pacific. Therefore, the effects of climate oscillations might have influenced species in dissimilar ways depending on the species' distribution.
2. We used mitochondrial DNA (mtDNA) and microsatellite DNA (msDNA) markers to clarify the evolutionary history of masu salmon Oncorhynchus masou subspecies-complex (family Salmonidae) distributed in historically non-glaciated regions in the western North Pacific.
3. No marked regional or subspecies-specific mtDNA haplotype associations were recognised, except for O. masou subsp., a lacustrine form endemic to Lake Biwa, an ancient lake in central Honshu. The landlocked subspecies O. masou formosanus, with a disjunct distribution on Taiwan Island, exhibited no diagnostic population features differing from the other subspecies, in either mtDNA or msDNA markers. Mismatch distribution and Bayesian skyline plot analyses indicated relatively recent range expansion and rapid population growth for masu salmon during the last glacial period (c. 0.1–0.15 Ma).
4. Contrary to the mtDNA genealogy, Bayesian clustering using msDNA showed two main genetic clusters, mainly northern populations of the subspecies O. m. masou and populations of the subspecies O. m. ishikawae in southern areas of the Japanese Archipelago. Notably, O. m. formosanus on Taiwan Island was included in the O. m. masou group, and O. masou subsp. was included in the O. m. ishikawae group.
5. Our results suggest that the masu salmon subspecies-complex in historically non-glaciated regions of the Temperate Northern Pacific is characterised by weak population structuring and shallow genetic differentiation among the subspecies, except for O. masou subsp. owing to its long isolation in Lake Biwa. Incomplete lineage sorting and historical inter-subspecies hybridisation, possibly due to secondary contact, seem to be plausible explanations for discrepancies in the mitochondrial DNA genealogy and nuclear DNA genetic structure.

     

Nuclear waste management activities in the pacific basin and regional cooperation on the nuclear fuel cycle

Abstract

Pacific Ocean and island sites have been used since World War II for nuclear activities, including effluent discharges from nuclear facilities, sea dumping of packaged radioactive wastes, and testing of nuclear explosives. In the future, the amounts of radioactive wastes deliberately released into the Pacific Ocean may increase in connection with planned commercial‐scale nuclear fuel reprocessing operations, recommencement of plutonium production for weapons purposes, and resumption of sea dumping of low‐level wastes. Proposed storage of spent nuclear fuel on Pacific island sites or disposal of high‐level wastes in the deep seabed of the Pacific could also expose the ocean to a risk of contamination by long‐lived radio‐nuclides. The consequences of all these activities should be assessed in practical terms—their likely effects on the living marine resources of the Pacific and the economic development of the societies benefited by them; in terms of the legal principles which govern activities such as marine radioactive waste disposal that could pollute the marine environment; and in relation to current and future organizational arrangements that could achieve political resolution of outstanding international nuclear energy issues. Despite the prospective dangers of marine nuclear activities, the use of relatively remote or extraterritorial marine locations including those in the Pacific basin for nuclear operations could provide a basis for international cooperation on management of the “back end”; of the nuclear fuel cycle, including storage and reprocessing of spent fuel and high‐level waste disposal. A broadly recognized international regime for the nuclear fuel cycle could be based on regional organization of such back‐end operations, provided local acceptance could be obtained.     

Long-distance dispersal of the beach strawberry,Fragaria chiloensis,from North America to Chile and Hawaii

Background and AimsThe beach strawberry, Fragaria chiloensis, is found in a narrow coastal band from the Aleutian Islands to central California and then jumps thousands of kilometres all the way to Hawaii and Chile. As it probably had a North American origin, it must have been introduced to the other locations by long-distance dispersal. The aim of this study was to determine which agent carried the beach strawberry to its Pacific and South American locations.MethodsA deductive framework was constructed to separate between the possible modes of long-distance dispersal involving animals, wind and ocean currents. Bird migration was subsequently identified as the most likely scenario, and then the routes, habitats, feeding preferences and flight distances of all the shorebird species were evaluated to determine the most likely carrier.Key ResultsSix species migrate between North America and Chile and feed on the beaches and rocky shores where F. chiloensis grows naturally: Black-bellied Plovers, Greater Yellowlegs, Ruddy Turnstones, Sanderlings, Whimbrels and Willets. Of these, only two eat fruit and migrate in long continuous flight: Ruddy Turnstones and Whimbrels. Two species travel between North America and Hawaii, eat fruit and forage on the beaches and rocky shores where F. chiloensis grows naturally: Pacific Golden-plovers and Ruddy Turnstones. Ruddy Turnstones eat far less fruit than Pacific Golden-plovers and Whimbrels, making them less likely to have introduced the beach strawberry to either location.ConclusionsWe provide evidence that F. chiloesis seeds were probably dispersed to Hawaii by Pacific Golden-plovers and to Chile by Whimbrels.     

Effect of cereal harvesting method on a recent population decline of Corn Buntings Emberiza calandra on the Western Isles of Scotland

Capsule Population decline since 1995 is associated with the harvesting of cereals as arable silage.

Aim To survey Corn Bunting populations on the Western Isles and test whether population changes since 1995 are associated with change in cereal harvesting methods.

Methods Twelve areas of machair on the Uists and Benbecula were re-surveyed in 2002, after previous surveys in 1983 and 1995. These and other areas of suitable habitat on these islands, plus Berneray, Baleshare, Vallay, Barra and Vatersay, were surveyed in 2003–05 to provide a breeding population estimate for the Western Isles. Cereal strips in the 12 core survey areas were mapped in 2002 and the timing and method of harvesting of each was recorded. Cattle-feeding stands in 24 crofting townships were visited in March 2003 to record the type of fodder available, measure grain abundance and ripeness in fodder samples, and record foraging Corn Buntings. Experimental trials tested whether Corn Buntings selected fodder with riper grain.

Results The Western Isles Corn Bunting population was estimated at 117 occupied territories in 2005, a decline of 17% since 2002/03, and of at least 62% since 1995. Population decline was greater in areas with higher proportions of the cereal area harvested as arable silage. Arable silage contained fewer and less-ripe grains than traditionally harvested cereal, and was less likely to attract feeding Corn Buntings. Corn Buntings preferred to feed on silage containing riper grain.

Conclusions The remaining Corn Bunting population of the Western Isles is declining rapidly, probably because of reduction in winter grain supply caused by change from traditional reaper-binder harvesting and stacking of fully ripe cereals to harvesting the crop as unripe or partially ripe arable silage. Management change to restore a supply of ripe grain over winter is likely to be essential if this population decline is to be halted and reversed.     

Chile's Presential sea proposal: Implications for straddling stocks and the international law of fisheries

Abstract

Despite rapid evolution in international fisheries law and establishment of the exclusive economic zone (EEZ), straddling stocks still remain susceptible to heavy harvesting in high seas areas by distant‐water fishing states there by undermining coastal state management. The notion mar presencial (presential sea) has recently been proposed by Chile as a solution for the problem of straddling stocks. The presential sea concept was nationally designed and promoted to curtail such foreign fishing in areas adjacent to Chile's EEZ. This article examines the presential sea as a geostrategic concept, its justification for being, and the question of its permissibility under contemporary international fisheries law. Attention is also given to recent international developments that challenge the legal viability of the presential sea concept. The authors conclude that if this concept were to be widely adopted by coastal states, the traditional freedom to fish on the high seas might be severely compromised. The preferable legal solution is to work within the parameters set out by the 1982 UN Convention on the Law of the Sea, more particularly through bilateral negotiations between coastal states and fishing states, as well as regional fishery commissions that could manage activities in the region.     

Comparative anatomy of the dorsal hump in mature Pacific salmon

Mature male Pacific salmon (Genus Oncorhynchus ) demonstrate prominent morphological changes, such as the development of a dorsal hump. The degree of dorsal hump formation depends on the species in Pacific salmon. It is generally accepted that mature males of sockeye (O. nerka ) and pink (O. gorbuscha ) salmon develop most pronounced dorsal humps. The internal structure of the dorsal hump in pink salmon has been confirmed in detail. In this study, the dorsal hump morphologies were analyzed in four Pacific salmon species inhabiting Japan, masu (O. masou ), sockeye, chum (O. keta ), and pink salmon. The internal structure of the dorsal humps also depended on the species; sockeye and pink salmon showed conspicuous development of connective tissue and growth of bone tissues in the dorsal tissues. Masu and chum salmon exhibited less‐pronounced increases in connective tissues and bone growth. Hyaluronic acid was clearly detected in dorsal hump connective tissue by histochemistry, except for in masu salmon. The lipid content in dorsal hump connective tissue was richer in masu and chum salmon than in sockeye and pink salmon. These results revealed that the patterns of dorsal hump formation differed among species, and especially sockeye and pink salmon develop pronounced dorsal humps through both increases in the amount of connective tissue and the growth of bone tissues. In contrast, masu and chum salmon develop their dorsal humps by the growth of bone tissues, rather than the development of connective tissue.