Abundance and Recovery Rates in Humpback novaeangliae) in the Mexican Pacific (1986-2006) whales (Megaptera S. Martínez-Aguilar, 1, J. Urbán R.1, and J. Barlow,2 1 .- Universidad Autónoma de Baja California Sur, Ap. Post 19-B, La Paz, Baja California Sur 23081, México 2 .- NOAA Southwest Fisheries Science Center, 3333 N. Torrey Pines Court, La Jolla, California 92037, USA. INTRODUCTION During the last two centuries commercial whaling for humpback whales (Megaptera novaeangliae) decreased the North Pacific stocks to near extinction. In 1965 the International Whaling Commission banned commercial whaling, when there were only around 1200 and 1400 whales in the North Pacific, since then, many countries have been conducting research to estimate the humpback whales abundance and recovery rates. Through photo-ID at the beginning of the 80’s, the North Pacific population was estimated between 1000 and 2000 individuals (Darling y Morowitz, 1986; Baker y Herman, 1987). Using data between 1990 and 1993; Calambokidis, et al., estimated the population between 6000 and 8000 individuals (Calambokidis et al., 2001). The most recent estimation for the North Pacific between 2004 and 2006 realized by the project SPLASH (Structure of Populations, Levels of Abundance and Status of Humpbacks), using Chapman-Petersen Model for closed populations, was of 21,808 individuals (CV=0.04) Barlow et al., (2011) and for the Mexican Pacific, Urbán et al., (1999) using the Jolly-Seber method, estimated the Mexican Pacific coastal population of humpback whales in 1813 individuals (95% CI: 918-2, 505) for the year 1992 and of 914 animals (95% CI: 590-1, 193) for the Revillagigedo Stock in 1991. In Mexico, humpback whales, are distributed mainly in three areas: The south part of the Baja California Peninsula (PBC), Mexican Pacific Coast (CPM) and at the Revillagigedo Archipelago (AR) (Rice, 1978; Urbán y Aguayo, 1987). METHODS Field work was conducted in Revillagigedo islands-Colima and in the Mexican Pacific Coast (Banderas Bay, Marías islands and Isabel island- Jalisco and Nayarit) from 1986 until 2006 and in the South part of the Baja California Peninsula from 1987 until 2006 (Figure 1). Different ship vessels were used (small boat, and ships), and there were not predetermined navigation patterns. Whales were photo-ID by the white and black coloration and by other marks in the ventral surface of the flukes (Katona and Whitehead, 1981). Figure 1. Localities where photo-ID work was conducted: (PBC) Baja California Peninsula, (CPM) Mexican Pacific Coast, including Isabel island and Banderas Bay in Jalisco-Nayarit; (IC) Clarión island and (IS) Socorro island, this last two are part of the Revillagigedo Archipelago. Fluke photographs were classified using the ventral pigmentation of the flukes (Glockner and Venus, 1983). The best ones from each region were put together in photo-ID catalogs and this were matched between each other digitally at least twice with the program ACDSee 2.5, there were eight different catalogs matched from different institutes: Universidad Autónoma de Baja California Sur (UABCS), Universidad Nacional Autónoma de México (UNAM), Humbolt State University (HSU) y Cornell University (CU). There were a total of 7191 photo-identified from adult whales. Those photos that were not optimum (Poorly focused, bad position, light exposure, etc.) were not compared in order to be sure of the results. For the absolute abundance estimations, we analyzed each congregation zone as independent units according to Urbán et al., (2000), proposed subdivision. For the data analysis we used Anne Chao Mth Model (1987). The analysis was made in the R program 2.12.0 (http://www.R-project.org/) and in the RMark 6. We used two sets of data with four years each (1987-1990 and 2003-2006), we obtained two estimations because of this, one at the beginning and one at the end. The estimations obtained with Chao’s Mth model (1987) were used to estimate the recovery rate of the population for each congregation, and the obtained values were analyzed according to an exponential growth model (Y = β0eβ1x). In order to know the annual recovery rate β1, we used the β1 =LN (Y / β0) / x formula. RESULTS We had 7191 photographs of humpback whales flukes. When we matched these photographs, we obtained 4244 different individuals; 1277 for the Baja California Peninsula (PBC); 1800 for the Mexican Pacific Coast (CPM) and 1672 for the Revillagigedo Archipelago (AR). This number of photo-identifications does not match the sum because of the recaptures between the congregation zones. Also for the absolute abundance estimation, we put together the photo identifications from Baja California Peninsula and the Mexican Pacific Coast, and eliminated the recaptures between them; we obtained 2805 individuals for this Coastal Stock, and we also put the three zones together for the Mexican Pacific Stock. This was in order to analyze them as congregation units and evaluate how the recovery rate modifies annually in this way. In the groups of data obtained (1987 to 1990 and 2003 to 2006), final abundance estimations with 95% Confidence Intervals are: Baja California Peninsula with 6820 individuals, Mexican Pacific Coast with 4149 individuals, Revillagigedo Archipelago with 2,352 individuals, Coastal Stock with 7051 individuals and 8168 individuals for the whole Mexican Pacific Stock (Table1). Table 1. Abundance estimations for the two data sets obtained with Mth Chao’s model. Congregation Estimation CI 95% 1987-1990 Estimation CI 95% 2003-2006 Baja California Peninsula 1262 624-2757 6820 4650-10181 Mexican Pacific Coast 1642 1121-2499 4149 3475-5012 Revillagigedo Archipelago 571 465-729 2352 2030-2762 Coastal Stock 1742 1304-2401 7031 6048-8236 Mexican Pacific Stock 1964 1612-2448 8168 7357-9112 Once we obtained the estimation for each of the five congregations, we analyzed the growth rates with the exponential growth formula, obtaining the following results (Table 2): Table 2. Annual recovery rate estimation of each of the congregations. Congregation Estimation 1987 1990 Estimation 2003 # years 2006 Annual Increase (%) (N) IC 95% (N) IC 95% Baja California Peninsula 1262 624-2757 6820 4650-10181 16 10.5 Mexican Pacific Coast 1642 1121-2499 4149 3475-5012 16 5.7 Revillagigedo Archipelago 571 465-729 2352 2030-2762 16 8.8 Coastal Stock 1742 1304-2401 7031 6048-8236 16 8.7 Mexican Pacific Stock 1964 1612-2448 8168 7357-9112 16 8.9 DISCUSSION The abundance estimation in the Baja California Peninsula N=6820, was the largest obtained, this could be because, it’s not only an aggregation zone, but it is also in the migratory path of the whales from the Coastal Mexican Pacific and from the Revillagigedo Archipelago whales, this can be seen in the 31% percent of the photographed whales in the Peninsula, have also been photographed in one of the other two congregations, which could create an over estimation in the Peninsula abundance. The abundance estimation in the Revillagigedo Archipelago N=2352 is similar to the one obtained with the Hilborn´s model during the SPLASH project (2003-2006), which was of 2600 individuals (Calambokidis et al., 2008). The estimation seems correct, since in this study there was a more homogenous space-time effort and because we found the majority of the animals congregated within a small sample area, the recapture rate of the individuals was the largest of the congregation zones. The Mexican Pacific Coast N=4149, one of the main bias in the recapture probability is because of the animal distribution, they can be distributed in more than 2000 km along the coast, and our sampling zone was of 200 linear km (between the Marías islands, Isabel island and Banderas Bay) which is the main aggregation zone in the coast, thus the animals that are distributed north of the Marías islands or south of the Banderas bay have less recapture probability, besides the sampling efforts were not the same in the zone. In order to reduce the bias in the Baja California Peninsula and the Mexican Pacific Coast, we estimated the abundance of the two congregations in what we named the Coastal stock, thus we eliminate the error of identifying those animals that belong to the CPM and not to the PBC, besides the recapture number increases, giving an estimation of 7031 animals. Finally, by putting together and analyzing every photo identification from the three congregation zones, we estimated the abundance for all of the Mexican Pacific Stock N=8128; this estimation is slightly bigger than the one obtained during SPLASH (2003-2006), which was of 6000-7000 individuals (Calambokidis et al., 2008). With the results obtained with Chao’s Mth model, we estimated that the recovery rates or annual growth for the winter aggregation zones are: Baja California Peninsula 10.5%, Mexican Pacific Coast 5.7%, Revillagigedo Archipelago 8.8%, Coastal Stock 8.7% and for the whole Mexican Pacific Stock 8.9%, which is why we can say that the recovery rate in general is between 8.7 and 8.9 %, considering that the recovery rate of the PCB could be biased by an overestimation of abundance because of the animals that are migrating through the area. The annual recovery rate obtained for the Mexican Pacific is a little higher than the annual recovery rate obtained for the US West Coast, estimated between 1988-1989 to 1997 Mizroch et al., (2004); it is also higher than the annual recovery rate of 8.1 % obtained for the North Pacific, during SPLASH project 2003-2006 (Barlow et al., 2011). And higher also than the 6.9 % obtained by Calambokidis et al., 2008 for the Mexican Pacific. It’s important to consider that of the 21808 humpback whales estimated in the North Pacific (Barlow et al,.2011); 8168 have been estimated for the Mexican Pacific, being a little more than 37% of the North Pacific population, which reflects the importance of these aggregation zones for the population. ACKNOWLEDGMENTS This work was realized under the permits from the Secretary of Environment Natural Resources and Fisheries (SEMARNAT), Natural Protected National Areas Commission (CONANP), Government Secretariat and Secretariat of Navy of Mexico and was realized with support from the projects “Cambio ambiental, dinámica de los hábitos de la ballena jorobada y conformación de la mastofauna marina en la boca del Golfo de California y las Islas Revillagigedo” (CONACyT 38605-V), “Habitos reproductivos e historia poblacional reciente de las ballenas jorobadas (Megaptera novaeangliae) en el Pacífico Mexicano (CONACyT 400302-5-3725PN). We would like to thank WWF-Telcel alliance, the SPLASH project (Structure of Populations, Levels of Abundance and Status of Humpbacks), WDCS and CONACyT (218125 scholarship), for the economic funds to realize this project. To the South West Fisheries Service Center for allowing us to process the data analysis in the institute. 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