Franciscana strandings on the north coast of Santa Catarina State and insights into birth period

Franciscana, Pontoporia blainvillei, is the most threatened small cetacean in the South Atlantic. Accidental captures in fishing nets is the main problem for this species throughout its distribution. Dead franciscanas found along the coast are an important source of information. This work aimed to analyze the records of dead franciscanas found on the northern coast of Santa Catarina, including Babitonga Bay. Between January 2001 Biotemas, 26 (4): 133-139, dezembro de 2013 ISSNe 2175-7925 http://dx.doi.org/10.5007/2175-7925.2013v26n4p133

Accidental capture in fishing nets is the main conservation issue for the species (SECCHI et al., 1997;KINAS, 2002;ROSAS et al., 2002;DI BENEDITTO, 2003;SECCHI et al., 2004;CAPOZZO et al., 2007).Hundreds of franciscana dolphins die each year as a consequence of getting entangled in gillnets.This problem led to the recognition of these animals as an endangered species (MMA, 2003;REEVES et al., 2008).
The occurrence of franciscana dolphins in Santa Catarina was first documented by Azevedo et al. (1982).Simões-Lopes and Ximenez (1993) presented more detailed information, including the individuals catalogued in Brazilian institutions, and information about strandings.In a review of the mammals of Santa Catarina State, Cherem et al. (2004) indicated that the species occurs along the coast of the whole state.Opportunistic sightings (FLORES, 2009), studies related to biological information, such as diet (CREMER et al., 2012), and comparative studies related to morphology (HIGA et al., 2002) and contamination (ALONSO et al., 2012;TORRE et al., 2012) are reported in the literature.
Despite the fact that Santa Catarina State has a strong fishery activity, including artisanal and commercial boats, little information is available on the levels of accidental captures of marine mammals.Simões-Lopes and Ximenez (1993) reported opportunistic information about cetacean interactions with fishing activities.Cremer et al. (1995) monitored for the first time a small artisanal fishery community at Farol de Santa Marta, in Laguna (28 o 36'S; 48 o 49'W).In that study, the authors estimated an annual capture of 120 franciscanas in that area.Henrique-Garcia et al. (2005) monitored a small artisanal fishery community in Barra Velha (26°38'S), and estimated a lower annual accidental capture.No information is available on the rate of accidental captures related to industrial fisheries.
On the northern coast of the state is a resident population in Babitonga Bay.This population was first recorded in 1996, and since then, some studies have been conducted with the aim of analyzing its ecology and behavior (CREMER; SIMÕES-LOPES, 2005;CREMER, 2007;CREMER;SIMÕES-LOPES, 2008;CREMER et al., 2012).This population was estimated at 50 individuals (CREMER; SIMÕES-LOPES, 2008).
The aim of this study was to present the records of franciscanas stranded dead on the northern coast of Santa Catarina State in the last twelve years to contribute to our knowledge of the species in this state, offering some insights into the birth period of the species in this region.

Material and Methods
In the period between January 2001 and November 2012 franciscana carcasses were recovered along the northern coast of Santa Catarina State, between coordinates 26°07'S and 26°38'S.Most of the records Franciscana strandings on Santa Catarina coast and birth period were opportunistic, and the animals were located according to information given by local community.Posters were distributed periodically along the coast asking the community to alert us about any marine mammal stranded on the beach.
When possible, the animals were measured (total linear length, following Norris, 1961) and sexed by visual examination according Berta and Sumich (2003).Females were checked for pregnancy.Carcasses between decomposition levels 2 and 5 were necropsied as indicated by Geraci and Lounsbury (1993).

Results and Discussion
Between January 2001 and November 2012, 54 franciscana carcasses were recovered, 19 (35.2%) of which were found in Babitonga Bay. Figure 1 shows the recovery locations.The skeletons were catalogued and deposited in the Acervo Biológico Iperoba mammal collection at Universidade da Região de Joinville (UNIVILLE), in São Francisco do Sul.
It was not possible to identify the sex for 26 individuals, and total length could not be determined for When possible, the animals were measured (total linear length, following Norris, 1961) and sexed by visual examination according Berta and Sumich (2003).Females were checked for pregnancy.Carcasses between decomposition levels 2 and 5 were necropsied as indicated by Geraci and Lounsbury (1993).

Results and Discussion
Between January 2001 and November 2012, 54 franciscana carcasses were recovered, 19 (35.2%) of which were found in Babitonga Bay. Figure 1 shows the recovery locations.The skeletons were catalogued and deposited in the Acervo Biológico Iperoba mammal collection at Universidade da Região de Joinville (UNIVILLE), in São Francisco do Sul.20 because of decomposition state of the animals.For some of these animals, the skeleton was not complete.
Stranding date was recorded for all animals.We recorded dead franciscanas every year of the study period, and we found the largest number in 2011 (Figure 2).The highest number of carcasses recovered was in August, September and October (Figure 3), which accounted for 28 (52%) of the carcasses.
The largest animal recorded was a 142 cm long female, stranded on the coast of Itapoá (26°04'S) (Figure 4).Ten individuals (18.5%) were less than 80 cm in length, indicating that they were calves or fetuses (ROSAS; MONTEIRO-FILHO, 2001;DANILEWICZ et al., 2002).Our data indicate that births occur between the months of October and January in Santa Catarina (Table 1).Two individuals  were surely fetuses, retrieved from the females: UNIVILLE 130 (37 cm) and UNIVILLE 322 (60.3 cm); the females were 138 cm and 142 cm in length, respectively.Applying the fetal growth rate of 7.55 cm/month estimated by Rosas and Monteiro-Filho (2001), the first fetus would have been born between November and December, and the second in November.The individuals between 60 and 70 cm could have been newborns or near-term fetuses.There is no information about reproductive parameters for franciscana dolphins in Santa Catarina State.Rosas and Monteiro-Filho (2001) presented information for São Paulo and Paraná states (25º00'S-25º58"S), concluding that franciscanas are born at 71.2 cm, mainly between October and December.It seems that franciscanas in Santa Catarina are smaller, but the birth period is the same.Simões-Lopes and Ximenez (1993) mentioned a female found in a gillnet in Camboriu (26 o 59'S) that aborted a near-term fetus in October.Cremer et al. (1995) reported the accidental capture of one pregnant and lactating female in July along Cape Santa Marta Grande (28 o 36'S), with a 20 cm long fetus.This fetus would have been born between January and February, considering the fetal growth rate estimated by Rosas and Monteiro-Filho (2001).
The small calves reported here were probably related to the accidental capture of their mothers in fishing nets.Despite the fact that Brazilian law forbids the use of fixed gillnets along the coast of Santa Catarina State (Portaria IBAMA 54/1999), the nets are used extensively.For Babitonga Bay, a specific law allows fishermen to use driftnets inside the bay (Portaria IBAMA 84/2002) throughout the year, and these nets are commonly used between October and November (PINHEIRO; CREMER, 2003).This kind of net is strongly related to incidental captures and could be considered a significant threat to this population.
Data collection was not uniform along the coast and over time, and therefore, the information presented here could not be used to estimate mortality.Ferreira et al. (2010) reported that the majority of carcasses of franciscanas accidentally caught in fishing nets do not strand on the beach.The highest number of records in Babitonga Bay was related not only to our proximity to the area, which facilitated gathering information, but also to the occurrence of a resident population there (CREMER; SIMÕES-LOPES, 2005; CREMER; SIMÕES-LOPES, 2011).The continuous monitoring of the coast over time shall provide more detailed information about this species.

FIGURE 1 :
FIGURE 1: Location of the carcasses of franciscanas on the north coast of Santa Catarina State (n=54) between January 2001 and November 2012.

FIGURE 1 :
FIGURE 1: Location of the carcasses of franciscanas on the north coast of Santa Catarina State (n=56) between January 2001 and November 2012.

FIGURE 2 :
FIGURE 2: Number of dead franciscana dolphins (n=54) recorded per year on the north coast of Santa Catarina State, January 2001 to November 2012.

FIGURE 3 :
FIGURE 3: Number of dead franciscana dolphins recorded (n=54) per month on the north coast of Santa Catarina State between January 2001 and November 2012.

FIGURE 4 :
FIGURE 4: Size classes of dead franciscana dolphins (n = 34) recorded on the north coast of Santa Catarina State between January 2001 and November 2012.