CCAMLR

More white-chinned petrels (Procellaria aequinoctialis) are accidentally killed in fisheries than probably any other seabird in the world, but the population impact of this mortality is poorly understood, partly because there have been no estimates of the species’ abundance in recent decades. The largest breeding aggregation, comprising the majority of the worldwide total, is believed to be on the sub-Antarctic island of South Georgia. We estimated the size of this population by calculating the area of suitable habitat and the density of occupied burrows within it. Just less than one million pairs of white-chinned petrels laid on South Georgia in the survey seasons (2005/06 and 06/07). This is 50% of the previous estimate, but still represents around two-thirds of the global population. If the population is declining due to fishery bycatch off S America, as is likely, the scale of annual mortality in this population alone is at least in the high tens of thousands, and plausibly hundreds of thousands.

This paper describes methods and results from a recent aerial survey of the macaroni penguin population at South Georgia.

We investigate the influence of krill (principally Euphausia superba) patchiness on the foraging distributions of seabirds to understand how variation in krill influences patch dynamics between krill and birds. At sea surveys were conducted near Elephant Island, Antarctica for three years (2004-2006) during the annual U.S. Antarctic Marine Living Resources (AMLR) program. Standardized strip-transect surveys were used to map seabirds, and a combination of acoustic and net surveys was used to map krill. We measured patch size of krill and seabirds and elucidated how krill patch dynamics influence foraging seabirds. The spatial association between krill and predators was influenced by the size and arrangement of krill patches. We found a negative relationship between abundance and patchiness of krill and predators, indicating that when krill is less abundant, krill and its predators are less abundant and concentrated. We conclude that annual patch dynamics of krill strongly influences the local abundance and distribution of seabirds. Such information should be used to interpret potential interactions between seabirds and krill fisheries operating near Elephant Island.

1. Implementing an ecosystem approach to fisheries management requires an effective ecosystem monitoring programme, the utility of which depends upon its ability (measured by the statistical power) to detect effects that trigger management action. 2. Using data from a long-term ecosystem monitoring programme of the predators of Antarctic krill Euphausia superba at South Georgia together with a krill population model to simulate natural and fisheries induced variability in krill abundance, the power to detect the effects of different levels of fishing was examined. 3. The power to detect the effects of fishing using either the krill population or a combined predator response index was low (20–40% power after 20 years with the probability of a type I error (α) = 0.05). The power increased to >50% when α was increased to 0.2 when the ability to detect change was greater with the predator response index than using the krill population itself. 4. The results indicate that although this monitoring programme has a proven ability to detect the effects of natural variability in krill abundance, its ability to detect the effects of fishing may be limited if there is a requirement for statistical significance at the 95% level. A situation where changing α produces a marked increase in statistical power, and the difference in the relative ecological costs of making type I and type II errors is likely to be high, may require a more flexible approach to choosing significance levels required to trigger management action. 5. Although long-term monitoring provides a wealth of basic ecological information it is essential to evaluate, the ability to detect specific changes in order that management action is not delayed because of an inability to detect an effect rather than the lack of an effect of the fishery.

The horizontal and vertical distribution and population structure of euphausiids in the Ross Sea and its adjacent waters were investigated during the summers of 2004/2005 using stratified towed samples. Nine species of euphausiids occurred in the survey area. Among them, Euphausia triacantha was dominant in biomass north of the southern boundary of the Antarctic circumpolar current (SB). Thysanoessa spp. was widely distributed north of the continental slope, while E. superba was distributed from the SB to the slope, where it showed the highest biomass. Juvenile E. superba was distributed offshore near the SB and remained at the surface, but gravid females were dominant in the slope and mainly occurred in the middle layers (400–600 m). Adult and juvenile E. crystallorophias were found at 200–300 m in the colder water of the continental shelf. In general, the peak biomass of euphausiids was found in the mid layers of the Ross Sea area. The life span and the number of spawns for major species are also discussed.

Small black spots have been noticed on the cephalothorax of Antarctic krill, Euphausia superba, since January, 2001. To study the nature of the black spots, the krill were sampled in the winter of 2003, 2006, and 2007 in the South Georgia region, the Antarctic Ocean. Histological observations revealed that the black spots were melanized nodules that were composed of hemocytes surrounding either bacteria or amorphous material. In the 2007 samples, 42% of the krill had melanized nodules. Most of the nodules had an opening on the body surface of the krill. A single melanized nodule often contained more than one type of morphologically distinct bacterial cell. Three bacteria were isolated from these black spots, and classified into either Psychrobacter or Pseudoalteromonas based on the sequences of 16S rRNA genes. More than three bacterial species or strains were also confirmed by in situ hybridization for 16S rRNA. The melanized nodules were almost always accompanied by a mass of atypical, large heteromorphic cells, which were not observed in apparently healthy krill. Unidentified parasites were observed in some of the krill that had melanized nodules. These parasites were directly surrounded by the large heteromorphic cells. Histological observations suggested that these heteromorphic cells were attacking the parasites. These results suggest the possibility that the krill had been initially affected by parasite infections, and the parasitized spots were secondary infected by environmental bacteria after the parasites had escaped from the host body.