Ice Seal Biomonitoring Program Report

Transcription

1 Ice Seal Biomonitoring Program Report To: The Ice Seal Committee From: The Arctic Marine Mammal Program Alaska Department of Fish and Game Submitted by Lori Quakenbush January

2 Bearded (Erignathus barbatus), ringed (Pusa hispida), spotted (Phoca largha), and ribbon (Histriophoca fasciata) seals are the species of Alaska s seals collectively called ice seals because of their association with sea ice and their dependence on it for resting, pupping, and molting. Ice seals are important components of the ecosystems of the Bering, Chukchi, and Beaufort seas and they are important to the subsistence based culture of Alaska Natives for food and raw materials. There are concerns regarding the status, health, and availability of ice seals due to changes occurring in thickness, persistence, and distribution of sea ice. All four species of ice seals have been petitioned for listing as threatened or endangered under the Endangered Species Act (ESA) because of the affects of climate change on sea ice. Ringed and bearded seals in Alaska were listed as threatened under the ESA in December 2012 due to the expectation that changes in sea ice and snow will have population level effects by the next century. Oil and gas activities, contaminants, and large biomass removals by commercial fisheries in the Bering Sea may also be affecting seal populations. Little, however, is known about the biology and ecology of ice seals and how changes in sea ice will affect their populations or how quickly. Population estimates for ice seals are not available now and are not likely to be available soon with enough precision to detect trends. Ice seals are widely distributed in remote, ice-covered waters making marine mammal surveys dangerous, difficult, and expensive. We can however, monitor indices to population abundance, health, and availability to subsistence hunters. Tracking these indices are of elevated importance now that ringed and bearded seals are listed as threatened under the ESA as the best way to monitor the status of these populations. By collecting and analyzing harvest information and biological samples from subsistence-harvested seals at selected locations annually, we can assess the health and status of each species. Such information can be obtained from sex and age of seals harvested, age at first reproduction, pregnancy rate, growth rate, body condition, diet, disease exposure, and parasite and contaminant load. The Arctic marine ecosystem is changing and data collected from this monitoring program provides a means to detect and monitor the affects of such changes. For example, we have detected a change in diet with all species of ice seals eating more fish and fewer invertebrates. Changes in growth rate, productivity, age at maturity, and body condition are also detectable by comparison among time periods. This project provides essential information on the health and status of ice seals and allows us to monitor, document, and evaluate changes in population status, availability to subsistence hunters, contaminants and other health factors. Summary of Results Seals sampled. Since 1998, 5,435 seals of all four species have been sampled in 11 villages (Table 1). In addition to the villages we work with directly, the North Slope Borough provides samples from Barrow and Wainwright each year. Stomachs analyzed. Of the 5,435 seals sampled 2,702 (50%) of the stomachs have been analyzed to identify prey (Table 2). 2

3 Tissues collected for genetics. Tissue from each seal is archived for genetic studies. Our preliminary analysis did not find any stock structure in ringed or bearded seals using samples from the harvest. We are not conducting any genetic studies currently but are archiving samples for future studies. Contaminants. Our contaminants data include organochlorine (OCs; e.g., pesticides) and trace metals (e.g., lead, mercury, and cadmium) for 35 ringed, 37 bearded, 23 spotted, and 9 ribbon seals collected between 2003 and We are working on publications to provide the baseline for each species in Alaska. We have begun to analyze samples collected in 2010 and 2011 for comparison so that we can see how levels are going up or down through time. These data will be shared with the agencies that address human health issues for diet recommendations, however the levels we have measured are lower than those found in ringed seals in Canada. Blood samples screened for disease exposure. Serum from blood can be used to determine what diseases seals have been exposed to. By monitoring exposure rates we can see what diseases may be more common. Blood is difficult to process in the field so our samples sizes are smaller. A total of 306 serum samples have been analyzed for disease exposure (Table 3). The prevalence of exposure to 12 disease agents is shown in Table 4. Parasites. Tissues (stomach, intestine, heart, liver, lung, gall bladder) from 171 seals have been collected for parasite screening to evaluate changes in parasite load or species composition (Table 5). We have received preliminary results for 72 seals. Pupping rate. We have analyzed the female reproductive tracts of 168 ringed, 117 bearded, 127 spotted, and 24 ribbon seals (Table 6). We received 57 reproductive tracts (13 ringed, 24 bearded, 16 spotted, one ribbon, and three from unknown species of seal) that have not been analyzed. Previous pregnancy rates, however,ranged from 82 94% for sexually mature females of all species. Bearded and ribbon seals had the highest pregnancy rate (94%), followed by spotted seals (87.5%); ringed seals had the lowest rate (82%; Table 6). Growth rate. We collect body measurements to look at body condition and length by year. These measurements tell us how fast seals are growing and how fat they are. We can compare the measurements by time period and see if seals are doing better or worse than another time period. Hunter Information. We use hunter questionnaires so that hunters can tell us how available seals are, whether seal numbers or when they hunt has changed. Hunters can also tell us their concerns and whether the seals they see are healthy or not. The information allows us to understand potential biases in the sample collection created by hunting practices, which allow us to better interpret our study results. The information gathered to date generally indicates that all species of seals are available to hunters at the same level as in the past and seals appear healthy (Table 7). We recently added questions regarding observations of seals hauling out on land to begin to establish a baseline in order to determine if it becomes more common in the future as the ice-free season lengthens. 3

4 Support of other projects. We provided samples from our archives of healthy seals for analysis to help determine the cause of an unusual mortality event (UME) involving mostly ringed, but also some bearded and spotted seals. We also evaluated contaminant levels of some of the UME seals (see Contaminants below). We support student projects on methods to analyzed diet (e.g., fatty acids, isotopes, fecal DNA). We provided blood serum to a lab in Norway for a project to determine if the marine mammal form of Brucella is different from the terrestrial mammal form. We also provide nasal swabs to determine if they can be used instead of blood for some disease screening. 4

5 Table 1. Number of seals sampled by village and species, Kaktovik Barrow Wainwright Point Hope Kotzebue Shishmaref Diomede* Nome Gambell Savoonga Hooper Bay Total Ringed ,732 Bearded ,274 Spotted , ,016 Ribbon Unknown Totals , ,435 * The National Science Foundation (OPP Grant # ) provided funding for the collection of samples from Little Diomede during The North Pacific Research Board provided partial funding for the collection and analysis of samples for all villages in NOAA Fisheries has provided the bulk of the funding for sample collection. Table 2. Number of stomachs analyzed by village and by species, Kaktovik Barrow Wainwright Point Hope Kivalina Kotzebue Shishmaref Diomede* Nome Gambell Savoonga Hooper Bay Total Ringed Bearded Spotted , ,274 Ribbon Totals , ,702 * The National Science Foundation (OPP Grant # ) provided funding for the collection of samples from Little Diomede during The North Pacific Research Board provided partial funding for the collection and analysis of samples for all villages in NOAA Fisheries has provided the bulk of the funding for diet analysis. 5

6 Table 3. Number of blood (serological) samples analyzed for each species by village between 1998 and Diomede * Shishmaref Kotzebue Pt. Hope Hooper Bay Total Ringed Bearded Spotted Ribbon Totals * The National Science Foundation (OPP Grant # ) provided funding for the collection of samples from Little Diomede ( ). Table 4. Serum antibody prevalence for 12 disease agents in bearded seals harvested near Point Hope, Kotzebue, Little Diomede, and Shishmaref, Alaska. Antibody prevalence No. positive/no. tested (%) Disease Agent Bearded seals 1998 and Ringed seals Brucella spp. 5/77 (6.5) 5/58 (8.6) Canine distemper virus 0/119 (0) 0/93 (0) Phocine distemper virus 0/136 (0) 0/93 (0) Phocine herpesvirus-1 39/102 (38.2) 14/84 (16.7) Phocine herpesvirus-2 0/23 (0) 0/5(0) Leptospira Bratislava 0/71 (0) 29/83 (34.9) Leptospira canicola 0/71 (0) 0/72 (0) Leptospira grippotyphosa 0/71 (0) 1/72 (1.4) Leptospira hardjo 0/71 (0) 1/72 (1.4) Leptospira icterrohemorrhagiae 0/71 (0) 15/72 (20.8) Leptospira Pomona 0/71 (0) 0/72 (0) Toxoplasma spp. 3/116 (2.5) 4/91 (4.3) 6

7 Table 5. Number of samples collected for parasite screening by village and species in Barrow Point Hope Kotzebue Shishmaref Nome Diomede Hooper Bay Total Ringed Bearded Spotted Ribbon Totals Table 6. Reproductive status by species of females sampled between 2000 and Immature 1 One ovulation 2 Ovulations and Unknown birth 3 No. Total Total No. No. % preg. No. % preg. No. % preg. mature % preg. repros. Ringed Bearded Spotted Ribbon Females are reproductively immature. 2 Females have ovulated once. 3 Females have ovulated more than once and given birth at least once. 7

8 Table 7. Summary of selected local knowledge questions regarding seal harvest by species between 2004 and Numbers are the percentage of respondents answering in the affirmative to selected questions. Responses of don t know are not included in this table. Location Point Hope Diomede Shishmaref Gambell Hooper Bay Species Question n = 23 n = 29 n = 14 n = 44 n = 73 Ringed Have numbers remained the same? Have numbers decreased? Have numbers increased? Are seals found in the same areas? Does the hunt occur at the same time? Do you try for certain types of this seal? What is the hunting season? Year round Sept Jun Jun; Sept Nov Aug May Sept May Bearded Have numbers remained the same? Have numbers decreased? Have numbers increased? Are seals found in the same areas? Does the hunt occur at the same time? Do you try for certain types of this seal? What is the hunting season? Year round Sept Jun May Jun Year round Aug Jun Spotted Have numbers remained the same? Have numbers decreased? Have numbers increased? Are seals found in the same areas? Does the hunt occur at the same time? Do you try for certain types of this seal? What is the hunting season? Year round Year round Jun; Sept Nov Year round Year round Ribbon Have numbers remained the same? Have numbers decreased? Have numbers increased? Are seals found in the same areas? Does the hunt occur at the same time? Do you try for certain types of this seal? Jan Jul; Apr Jun; Oct May Jun; Nov What is the hunting season? Nov-Dec May Jun; Oct Nov Year round 8