Reproductive biology of Patagonotothen ramsayi (Regan, 1913) (Pisces: Nototheniidae) around the Falkland Islands

The reproductive biology of one of the most abundant notothenioids, Patagonotothen ramsayi, was investigated between February 2003 and November 2004 on the Falkland and Patagonian Shelves (Southwest Atlantic). Male and female P. ramsayi were mature at 27.6 and 24.8 cm L _T, respectively. P. ramsayi is a total spawner, with a total fecundity ranging between 24,300 and 76,700 eggs. Spawning occurs on the shelf breaks between June and August with the peak in gonado-somatic indices in June. Analysis of length frequency distributions over the year and sex ratios of mature fish during the spawning season may indicate the presence of a nesting and nest guarding behaviour in male fish, similar to other rockcods. Features of its reproductive strategy, which enabled P. ramsayi to dominate the medium-sized demersal fishes on the Patagonian shelf are discussed and compared with those of other nototheniids and cottid sculpins from the Northern Hemisphere.     

Age and growth of a sub-Antarctic notothenioid, Patagonotothen ramsayi (Regan 1913), from the Falkland Islands

The Falklands’ rockcod Patagonotothen ramsayi was aged successfully using whole and sectioned otoliths. Marginal increment analysis showed that one opaque and one translucent zone were laid down each year. Counting daily rings in juvenile fish and back calculating to their assumed hatch dates validated the first annulus. Readings taken from scales and otoliths showed good agreement with no significant difference between them (P>0.05). Inter- and intra-reader comparisons also showed good agreement. The maximum estimated age was found to be 14 years and the calculated von Bertalanffy growth curve L _T =33.77(1−e ^{−0.25year(t+1.07)}) showed that P. ramsayi is a relatively slow growing fish that attains 5–6 cm L _T in its first year and after which grows approximately 3 cm per year until 4 years. Males seemed to have a slightly lower growth rate but attained a greater maximum size than females. The formation of annuli in the otoliths of P. ramsayi seems to coincide with periods of high reproductive activity with both peaks in GSI and the prevalence of translucent margins occurring in July.     

What is out there: diversity in feeding of gentoo penguins (Pygoscelis papua) around the Falkland Islands (Southwest Atlantic)

During austral spring 2000, the diet of Gentoo penguins, Pygoscelis papua, was studied and compared to prey availability, assessed by trawl and plankton surveys, in waters adjacent to a number of colonies along the coast of West Falkland. There was good agreement in size and abundance of key prey species in the penguin diet and from the plankton and trawl surveys. The diet of birds breeding adjacent to shallow sheltered waters was dominated by demersal species, in particular crustaceans, Munida spp. whilst birds breeding adjacent to deeper exposed waters generally preyed upon pelagic species of fish, Falkland herring Sprattus fuegensis and squid, Moroteuthis ingens. Gentoo penguins generally foraged at depths of up to 30 m, relatively close to the coast, and illustrated a certain degree of selection of prey species where possible, thus providing evidence that they are not fully opportunistic predators.     

Distribution and abundance of the squid Moroteuthis ingens (Cephalopoda: Onychoteuthidae) in the Falkland Islands region of the South Atlantic

The distribution and abundance of the onychoteuthid squid Moroteuthis ingens were assessed for the Patagonian Shelf in the Falkland Islands region. Catch records from the commercial fishery and a research cruise were recorded from 1988 to 1996. Sampling included benthic, pelagic and semi-pelagic trawls and jigging. Moroteuthis ingens was recorded from 1,414 stations out of a total of 9,060 stations with 79.9% of all positive stations being from benthic trawls. Catch size ranged up to approximately 3,000 kg. The length frequency analysis and maturity indices suggested a major recruitment onto the shelf in September with a movement off the shelf during winter. There appears to be a lack of mature females on the Patagonian Shelf, indicating that females migrate into deeper offshore water to spawn. Observations of predation on Moroteuthis ingens on the Patagonian Shelf, along with a literature review, revealed that at least 4 mammal, 17 bird and 13 fish species prey on this squid. Received: 30 October 1997 / Accepted: 11 April 1998     

The diet of feral cats at New Island, Falkland Islands, and impact on breeding seabirds

We studied the diet of feral cats (Felis catus) on New Island, Falkland Islands, through the analysis of 373 scats collected during the austral summers of 2004/2005 and 2005/2006. The most frequent prey were three introduced mammals (house mice Mus musculus, ship rats Rattus rattus and rabbits Sylvilagus sp.) and the thin-billed prion Pachyptila belcheri (each season present on ca. 21% of the analysed scats). These represent the first systematic data on feral cat diet for the Falklands. A simple bioenergetics model suggests that cats could be eating in the region of 1,500–11,000 prions per season, representing <1% of the local adult and subadult population. Predation on other seabirds nesting on New Island (several penguin species, albatrosses and cormorants) was unimportant, with the possible exception of white-chinned petrels Procellaria aequinoctialis, which nest locally in very small numbers. For each prion eaten, cats were estimated to have killed 1.1–1.9 ship rats during the summer season, and probably more in autumn and winter. Knowing that ship rats are prion predators, it is conceivable that, on the whole, cats are having a positive impact on the prion population, a scenario predicted by general theoretical models. Thus, considering the available information, we would not recommend the implementation of any eradication programme on New Island that would target cats in isolation. Nevertheless, it would be prudent to consider some local action targeting cats and rats around the small New Island white-chinned petrel colony.     

Utilization of offal and discards from "finfish" trawlers around the Falkland Islands by the Black-browed Albatross Diomedea melanophris

Multinational fisheries operating in the vicinity of the Falkland Islands currently take c. 90,000 tonnes of true fish ("finfish" as opposed to squid) per annum, including hakes Merluccius spp., Southern Blue Whiting Micromesistius australis, Hoki Macruronus magel-lanicus and Red Cod Salilota australis, and generate substantial quantities of fisheries waste in the form of discards and offal. This paper examines the use made of this waste by scavenging Black-browed Albatrosses Diomedea melanophris which breed in the Falklands. The various types of waste produced are described and their consumption by scavenging albatrosses is quantified. The results indicate that Black-browed Albatrosses obtain c. 8000 tonnes of food per annum from this source, of which two-thirds is offal and the remainder whole discards. The energy content of this waste is equivalent to 4.4% of the estimated total annual energy requirements of the Falklands Black-browed Albatross population. However, as the fishery is a greater predator of finfish stocks than are the albatrosses, its long-term impact may be detrimental to these birds.     

Estimating the impact of interactions between bottlenose dolphins and artisanal fisheries around the Balearic Islands

Interactions between marine mammals and fisheries are a growing problem, and effective management requires assessment of the factors driving the interaction and of the impacts on fisheries. We used data from interactions between artisanal fisheries and bottlenose dolphins around the Balearic Islands to assess these factors and impacts. Observers collected data during 1,040 fishing operations over 3 yr. Location and year were important factors affecting interaction probability, with some areas showing large increases over the study period. We estimated the combined cost of catch loss and net damage as 6.5% of the total catch value (95% CI ?12.3%, ?1.6%), and the annual loss to be 3.4% (95% CI ?6.5%, ?0.1%) of the total catch by weight. This weight equates to the dietary needs of ～12 dolphins (95% CI 0.2, 22), suggesting the fishery is not a vital food source for the dolphin population. Two dolphins died through entanglement during the observed fishing operations. We observed 3% of the total fishing activity, by weight, in 2003; scaling up this mortality directly suggests that as many as sixty dolphins may be dying in nets each year. This interaction likely has serious conservation implications for the dolphin population.     

External nutrient inputs into terrestrial ecosystems of the Falkland Islands and the Maritime Antarctic region

Antarctic terrestrial ecosystems are nutrient-poor and depend for their functioning in part on external nutrients. However, little is known about the relative importance of various sources. We measured external mineral nutrient sources (wind blown material, precipitation and guano) at three locations, the cold temperate oceanic Falkland Islands (51°76′S), and the Maritime Antarctic Signy (60°71′S) and Anchorage Islands (67°61′S). These islands differ in the level of vegetation development through different environmental constraints and historical factors. Total mineral nitrogen input differed considerably between the islands. During the 3 month summer period it amounted to 18 mg N m⁻² on the Falkland Islands and 6 and 102 mg N m⁻² at Signy and Anchorage Islands, respectively. The high value for Anchorage was a result of guano deposition. By measuring stable isotopic composition (δ¹⁵N) of the different nitrogen sources and the dominant plant species, we investigated the relative utilisation of each source by the vegetation at each island. We conclude that external mineral nitrogen inputs to Antarctic terrestrial ecosystems show great spatial variability, with the local presence of bird (or other vertebrate) colonies being particularly significant.     

An example of the seasonal impact of sheep on colonisation by deciduous trees

Summary

Seasonal grazing treatments were begun in 1990 on two sites of bilberry moorland that lay 60–200 m from a strip of riverside woodland in Northern England. Treatments were summer grazing, winter grazing, year-round and no grazing, fences being moved in mid April and mid October each year to open or close plots. The main plant species, Calluna vulgaris, Empetrum nigrum and Vaccinium myrtillus, showed negligible response in cover or height to season of grazing, but colonisation by deciduous trees was much affected. On plots given summer protection (total area 2000 m²) 249 Sorbus aucuparia saplings were counted in 2000, together with one Quercus robur sapling, but no saplings were found in summer-grazed and year-round-grazed plots. Each winter the rowan saplings in the summer-protected plots were severely browsed by sheep, but they recovered in the next growing season. Their increasing trunk diameter and shoot increment up to 2000 suggested that some would soon escape herbivore control. But the fence moves did not take place in 2001,and in April 2002 these saplings were found to have been very heavily browsed. Nearly all survived but regrowth was much poorer in summer 2002 than summer 2000, so several more years of recovery are needed before it can be decided if summer protection from grazing allows succession to woodland at these sites.     

Variations in the parasite fauna of the Patagonian toothfish (Dissostichus eleginoides Smitt, 1898), with length, season, and depth of habitat around the Falkland Islands

The parasite fauna of Dissostichus eleginoides was examined from locations around the Falkland Islands. In total, of 11,362 individual parasites of 27 taxa were recovered from 105 fish. Two species, Ceratomyxa dissostichi and Sphaerospora dissostichi, represent new host records. The nematode Ascarophis nototheniae and the larval acanothocephalan Corynosoma bullosum were found to be new locality records and add to the knowledge of the biogeography and host specificity of parasites on the Patagonian Shelf. There were no significant differences in the mean abundance and prevalence of parasites recovered between sexes. Therefore, sex was not considered in further analysis and the data were pooled. Cysts of unknown etiology (CUE), the monogenean Neopavlovskioides georgianus, the larval acanthocephalan Corynosoma bullosum, and the digenean Neolepidapedon magnatestis had significant positive correlations with increasing host length. The larval Trypanorhynch cestode Grillotia erinaceus and the digenean Elytrophalloides oatesi showed significant negative correlations with increasing host length. CUEs, N. georgianus, the digenean Gonocerca physidis and E. oatesi showed statistically significant prevalence between summer, winter, and spring. The effect of depth on parasite communities was also examined, initially using a linear discriminant function analysis. The prevalence of individual parasites was then compared between depth strata using the chi-square test. The parasite communities on the shelf and deep water (> 1,000 m) were found to be different, whereas those caught at intermediate depths on the shelf slope were found to have parasite communities that were intermediate, containing a mixture of shelf and deeper-water parasites. The causes of the variations in parasite faunas in association with these intrinsic and extrinsic factors are discussed.     

Assessing the impact of toothed whale depredation on socio-ecosystems and fishery management in wide-ranging subantarctic fisheries

Marine predators feeding on fisheries catches directly on the fishing gear, a behaviour termed “depredation”, has emerged as a major human-wildlife conflict globally, often resulting in substantial socio-economic and ecological impacts. This study investigated the extent of this conflict in commercial Patagonian toothfish (Dissostichus eleginoides) fisheries across subantarctic waters where both killer whales (Orcinus orca) and sperm whales (Physeter macrocephalus) feed on toothfish caught on longline hooks. Using long-term datasets from six major fishing areas, from southern Chile to the Indian Ocean sector of the Southern Ocean, statistical models were developed to quantify the catch removals due to whale depredation interactions. The results indicated that these removals were large, totalling more than 6600 t of toothfish between 2009 and 2016 with an annual mean of 837 t [95% CI 480–1195 t], comprised of 317 t [232–403 t] and 518 t [247–790 t] removed by killer whales and sperm whales, respectively. Catch removals greatly varied between areas, with the largest estimates found at Crozet, where on average 279 t [179–379 t] of toothfish per year, equivalent to 30% [21–37%] of the total catches. Together, these findings provide metrics to assess the impacts of depredation interactions on the fishing industry, whale populations, fish stocks and associated ecosystems. With an estimated $15 M USD worth of fish depredated every year, this study highlights the large geographic scale and economic significance of the depredation issue and its potential to compromise the viability of some toothfish fisheries which are the primary socio-economic activity in subantarctic regions.

     

Caligus nolani n. sp. (Copepoda: Caligidae), a parasite of Patagonotothen sima (Richardson) (Teleostei: Pisces) from the Falkland Islands,and a note on Clavella bowmani,Kabata, 1963 (Copepoda: Lernaeopodidae)

Both sexes of a new species of parasitic copepod, Caligus nolani (Caligidae: Siphonostomatoida) from the skin of the nototheniid fish Patagonotothen sima from the Falkland Islands, are described. The male differs superficially from the female in having a more rounded cephalothoracic shield, a thinner genital complex and a two-segmented abdomen. C. nolani can be separated from all other species of Caligus by the shapes of the sternal furca and second antenna. Clavella bowmani Kabata, 1963 from P. sima is the first record of this species from the Falkland Islands.     

Patrilocality and recent migrations have little impact on shaping patterns of genetic structure of the armenian population

In general, genetic distances between human populations (also within one ethnic group) are larger for the Y chromosome markers than for the mtDNA. It is usually explained by higher rate of female versus male migration due to the cultural practice of patrilocality, when women move to their husbands’ residence after marriage. Recently found a reversed picture for the genetic variation in some ethno-territorial groups confirm the strict role of cultural traditions in shaping patterns of populations’ genetic structure. To test the role of patrilocality for the genetic structure of the Armenian population, we compared the Y chromosome and the mtDNA haplotype variations among and between geographical groups identified according to paternal (maternal) grandparental place of birth, from one side, and the populations currently living in the same geographical areas, from the other side. The results demonstrate that the Armenian population is regionally more structured for the Y chromosome than for the mtDNA. Additionally, in spite of expressed directivity of migration processes (caused by the phenomenon of patrilocality as well), the patterns of genetic variations for the populations of the same geographic areas remain without any significant changes during the last three generations.     

A continuous model of biomass size spectra governed by predation and the effects of fishing on them

A new time-dependent continuous model of biomass size spectra is developed. In this model, predation is the single process governing the energy flow in the ecosystem, as it causes both growth and mortality. The ratio of predator to prey is assumed to be distributed: predators may feed on a range of prey sizes. Under these assumptions, it is shown that linear size spectra are stationary solutions of the model. Exploited fish communities are simulated by adding fishing mortality to the model: it is found that realistic fishing should affect the curvature and stability of the size spectrum rather than its slope.     

Spatial differences and seasonal changes of net carbonate accumulation on some coral reefs of the Ryukyu Islands, Japan

This study sought to understand short-term spatial changes in accretion and erosion on (experimental) carbonate blocks on three coral reefs of the Ryukyu Islands, Japan. The principal objectives were to differentiate net accretion/erosion according to season, location, depth and substrate-type. At all locations the summer season showed more positive net weight changes and higher coralline algal coverage than the winter season. Windward reefs revealed higher net accretion and higher coralline algal coverage than leeward reefs. Massive (Holocene) Porites blocks showed highest net loss, followed by Pleistocene carbonate and (Holocene) Acropora blocks. High population densities of Echinometra mathaei (de Blainville) were recorded on reefs adjacent to large human populations and overall net carbonate loss significantly correlated to densities of E. mathaei type A.     

Only a matter of time: the impact of daily and seasonal rhythms on phytochemicals

Phytochemistry Reviews - Plants regulate molecular bioactivity in response to daily and seasonal environmental fluctuations in temperature, light, humidity, and precipitation. These rhythms...     

Infection of Sphyrion laevigatum (Copepoda: Sphyriidae) on Genypterus blacodes (Pisces: Ophidiidae) from the Falkland Islands,South Atlantic

The degree of parasitism by the parasitic copepod Sphyrion laevigatum on kingclip Genypterus blacodes in the Falkland Islands was investigated. In a sample of 719 kingclip, ranging in size from 35 to 145 cm total length, the prevalence of infection was 49%. The number of parasites per fish ranged from 0 to 24, with only 2% of the sample having more than 5 parasites. There was a significant increase in mean abundance of parasites with increasing fish age and length (P < 0.01 and P < 0.05, respectively). In addition, there was a significant difference in the prevalence in 1 of 3 geographical areas for the largest size class.     

The impact of seasonal and year-round transmission regimes on the evolution of influenza A virus

Punctuated antigenic change is believed to be a key element in the evolution of influenza A; clusters of antigenically similar strains predominate worldwide for several years until an antigenically distant mutant emerges and instigates a selective sweep. It is thought that a region of East-Southeast Asia with year-round transmission acts as a source of antigenic diversity for influenza A and seasonal epidemics in temperate regions make little contribution to antigenic evolution. We use a mathematical model to examine how different transmission regimes affect the evolutionary dynamics of influenza over the lifespan of an antigenic cluster. Our model indicates that, in non-seasonal regions, mutants that cause significant outbreaks appear before the peak of the wild-type epidemic. A relatively large proportion of these mutants spread globally. In seasonal regions, mutants that cause significant local outbreaks appear each year before the seasonal peak of the wild-type epidemic, but only a small proportion spread globally. The potential for global spread is strongly influenced by the intensity of non-seasonal circulation and coupling between non-seasonal and seasonal regions. Results are similar if mutations are neutral, or confer a weak to moderate antigenic advantage. However, there is a threshold antigenic advantage, depending on the non-seasonal transmission intensity, beyond which mutants can escape herd immunity in the non-seasonal region and there is a global explosion in diversity. We conclude that non-seasonal transmission regions are fundamental to the generation and maintenance of influenza diversity owing to their epidemiology. More extensive sampling of viral diversity in such regions could facilitate earlier identification of antigenically novel strains and extend the critical window for vaccine development.