[Federal Register Volume 80, Number 56 (Tuesday, March 24, 2015)]
[Notices]
[Pages 15557-15563]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2015-06749]


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DEPARTMENT OF COMMERCE

National Oceanic and Atmospheric Administration

[Docket No. 141015853-4853-01]
RIN 0648-XD563


Endangered and Threatened Wildlife and Plants; Notice of 12-Month 
Finding on a Petition To List the Harbor Porpoise (Phocoena phocoena) 
in the Baltic Sea as an Endangered or Threatened Distinct Population 
Segment (DPS) Under the Endangered Species Act (ESA)

AGENCY: National Marine Fisheries Service (NMFS), National Oceanic and 
Atmospheric Administration (NOAA), Commerce.

ACTION: Notice of 12-month Finding.

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SUMMARY: We, NMFS, announce a 12-month finding on a petition to list 
the harbor porpoise (Phocoena phocoena) in the Baltic Sea as an 
endangered or threatened distinct population segment (DPS) under the 
Endangered Species Act of 1973, as amended. We conducted a DPS analysis 
based on our joint U.S. Fish and Wildlife Service and NMFS DPS Policy. 
Based on the best available scientific and commercial information, we 
find that the harbor porpoise population in the Baltic Sea is not a DPS 
because it does not meet the criterion for significance outlined by our 
DPS Policy. Thus, we find this population is not warranted for listing.

DATES: This finding was made on March 24, 2015.

ADDRESSES: Information used to make this finding is available for 
public inspection by appointment during normal business hours at NMFS, 
Office of Protected Resources, 1315 East West Highway, Silver Spring, 
MD 20910. The petition and a list of the references we used can also be 
found at http://www.nmfs.noaa.gov/pr/species/petition81.htm.

FOR FURTHER INFORMATION CONTACT: Heather Coll, NMFS, Office of 
Protected Resources, (301) 427-8455.

SUPPLEMENTARY INFORMATION: 

Background

    On July 15, 2013, we received a petition from the WildEarth 
Guardians to list 81 marine species or subpopulations as threatened or 
endangered under the Endangered Species Act (ESA). We found that the 
petitioned actions may be warranted for 24 species and 3 
subpopulations, announced the initiation of status reviews, and 
solicited information from the public for each of the 24 species and 3 
subpopulations (78 FR 63941, October 25, 2013; 78 FR 66675, November 6, 
2013; 78 FR 69376, November 19, 2013; 79 FR 9880, February 21, 2014; 
and 79 FR 10104, February 24, 2014). We completed comprehensive status 
reviews under the ESA for six foreign marine species and evaluated 
whether one foreign marine subpopulation met our DPS Policy criteria in 
response to the petition (79 FR 74954; December 16, 2014).
    This notice addresses the finding for one of the petitioned 
subpopulations: a putative Baltic Sea harbor porpoise (Phocoena 
phocoena) subpopulation (79 FR 9880; February 21, 2014). The remaining 
species and subpopulation will be addressed in subsequent findings.
    We are responsible for determining whether species are threatened 
or endangered under the ESA (16 U.S.C. 1531 et seq.). To make this 
determination, we first consider whether a group of organisms 
constitutes a ``species'' under the ESA, then whether the status of the 
species qualifies it for listing as either threatened or endangered. 
Section 3 of the ESA defines a ``species'' as ``any subspecies of fish 
or wildlife or plants, and any distinct population segment of any 
species of vertebrate fish or wildlife which interbreeds when mature.'' 
On February 7, 1996, NMFS and the U.S. Fish and Wildlife Service 
(USFWS; together, the Services) adopted a policy describing what 
constitutes a DPS of a taxonomic species or subspecies (the DPS Policy; 
61 FR 4722). The DPS Policy identified two elements that must be 
considered when identifying a DPS: (1) The discreteness of the 
population segment in relation to the remainder of the species (or 
subspecies) to which it belongs; and (2) the significance of the 
population segment to the remainder of the species (or subspecies) to 
which it

[[Page 15558]]

belongs. As stated in the joint DPS Policy, Congress expressed its 
expectation that the Services would exercise authority with regard to 
DPSs sparingly and only when the biological evidence indicates such 
action is warranted. Listing determinations under the ESA must be based 
on the best available scientific and commercial information.
    Under the DPS Policy, a population segment of a vertebrate species 
may be considered discrete if it satisfies either one of the following 
conditions:
    (1) It is markedly separated from other populations of the same 
taxon as a consequence of physical, physiological, ecological, or 
behavioral factors. Quantitative measures of genetic or morphological 
discontinuity may provide evidence of this separation.
    (2) It is delimited by international governmental boundaries within 
which differences in control of exploitation, management of habitat, 
conservation status, or regulatory mechanisms exist that are 
significant in light of section 4(a)(1)(D) of the Act.
    If a population segment is considered discrete under one or more of 
the above conditions, we will evaluate its biological and ecological 
significance. The significance consideration may include the following:
    (1) Persistence of the discrete population segment in an ecological 
setting unusual or unique for the taxon,
    (2) Evidence that loss of the discrete population segment would 
result in a significant gap in the range of a taxon,
    (3) Evidence that the discrete population segment represents the 
only surviving natural occurrence of a taxon that may be more abundant 
elsewhere as an introduced population outside its historic range, or
    (4) Evidence that the discrete population segment differs markedly 
from other populations of the species in its genetic characteristics.

Species Description

    The harbor porpoise, Phocoena phocoena, is a widely distributed 
cetacean found in temperate and subarctic coastal and offshore waters 
of the northern hemisphere and is usually seen in groups of two to five 
animals (Reeves et al., 2002). Although it is sometimes found in 
offshore waters, it is primarily considered a coastal species limited 
to continental shelf waters (Perrin et al., 2002; Hammond et al., 
2008), possibly due to feeding preference and reproduction. It is also 
commonly found in bays, estuaries, harbors, and fjords (Powell et al., 
2002).
    Harbor porpoises are easy to identify because they are smaller than 
most other cetaceans in the northern hemisphere. Males can reach up to 
1.57 m in length and 61 kg in weight, while females reach up to 1.68 m 
and 76 kg (Reeves et al., 2002). They reach maximum girth just ahead of 
the dorsal fin, which gives them a robust body and short back (Reeves 
et al., 2002). They are medium to dark gray with a white belly and 
throat, a short blunt beak, and a medium-sized triangular dorsal fin. 
Their maximum life span is thought to be 24 years (Reeves et al., 
2002). Data from the Baltic Sea indicates that females are larger than 
males in all age classes (Benke et al., 1997).
    Despite their small size, harbor porpoises are highly mobile 
animals. Satellite tagging studies show that harbor porpoises have an 
average swim speed of 0.6-2.3 km/h, can swim distances of up to 58 km/
day, and have large home ranges (Read and Westgate, 1997; Sveegaard et 
al., 2011). This movement likely has implications for reproduction, 
foraging behavior, bioenergetics, environmental preferences, and 
population structure.
    Sexual maturity is generally reached at about 3 to 4 years, with a 
large proportion of mature females producing a calf every year (Read 
and Hohn, 1995; Koschinski, 2002; Reeves et al., 2002). Gestation lasts 
10--11 months (Reeves et al., 2002). Mean conception date is reported 
as 6 July  9.5 days in the Bay of Fundy and Gulf of Maine 
and 25 July  20.3 days in the Kattegat and Skagerrak seas 
in the Baltic region (Borjesson and Read, 2003). Timing of conception 
was found to be significantly earlier in the Baltic Sea (18 August 
 11.8 days) than in the North Sea, but did not differ 
between the Kattegat and Skagerrak (Borjesson and Read, 2003). The 
North Atlantic harbor porpoise sex ratio has been reported as biased 
toward males throughout life (Lockyer, 2003). The sex ratio found in 
Danish waters in the Baltic region is 55:45, male:female (Clausen and 
Andersen, 1988; Sorensen and Kinze, 1994).
    It is thought that shallow water areas are important for harbor 
porpoise calving, nursing, or breeding (Kinze, 1990; Hammond et al., 
1995). Calving areas in the Baltic region have been identified inside 
the 20-meter depth contour in the northern part of the Little Belt, 
Great Belt, Sejro Bight, waters north of Fyn, archipelago south of Fyn, 
and Smalandsfarvandet (Kinze, 1990). The significantly higher 
proportion of calves off Sylt and Amrum in the North Sea indicates that 
these coastal waters are used as a preferred calving ground for North 
Sea harbor porpoises (Kremer et al., 1990; Sonntag et al., 1999). North 
Sea harbor porpoises have also been found in high densities during 
summer at the tip of Jylland in the northern part of the Danish North 
Sea, 30km from the Danish coast at Horns Rev, and also in the German 
Bight (Teilmann et al., 2008), suggesting possible calving areas or 
even foraging areas.
    Harbor porpoises' small size, high mobility, and relatively fast 
reproduction cycle require a great deal of energy (Read, 1999; Koopman 
et al., 2002; MacLeod et al., 2007). For this reason, they feed on high 
lipid content fishes (Perin et al., 2002), though preferred prey 
species can vary regionally based upon availability (Koschinski, 2002; 
Perrin et al., 2002; Hammond et al., 2008). Harbor porpoises are 
solitary feeders and do not cooperatively forage (Reeves et al., 2002). 
Herring, sprat, and cod have been reported as the most important 
schooling fish prey items in the Baltic Sea (Koschinski, 2002), and 
harbor porpoises in Polish Baltic waters have been reported to feed on 
herring, sprat, and gobies (Malinga et al., 1997). Harbor porpoises in 
the Baltic Sea feed opportunistically on certain species found in their 
local area (Koschinski, 2002), and this may be the explanation for 
significant differences in species preference when compared to harbor 
porpoises in other areas, such as the North Sea (Benke et al., 1998). 
Harbor porpoises in the Kattegat and Skagerrak seas are reported to 
feed on Atlantic herring as juveniles and Atlantic hagfish as adults 
(Boerjesson et al., 2003).
    Long-distance migrations of Baltic harbor porpoises were thought to 
occur in the past (Mohl-Hansen, 1954; Wolk, 1969; Andersen, 1982; 
Gaskin, 1984). This assumption of a massive seasonal migration has 
since been challenged in the literature (Kinze, 2008; Andersen and 
Clausen, 1993), and modern telemetry research in the Baltic region has 
shown there to be more of a seasonal net movement rather than complete 
seasonal migration (Read and Westgate, 1997; Teilmann et al., 2008; 
Sveegaard et al., 2011).
    Environmental conditions may drive some of their net movement. 
Decreasing access to food or air and ice entrapments could occur when 
the Baltic Sea almost completely freezes during harsh winters, causing 
reports of mass deaths of harbor porpoises (Teilmann and Lowry, 1996). 
There are severe ice conditions reported in the southeastern Baltic 
Sea, but they are not consistent (Seina and Palusuo, 1996). There have 
been several winters with almost complete ice coverage in the Baltic 
Sea, which would have forced harbor porpoises from the Baltic Sea

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into the Belt Sea (Teilmann and Lowry, 1996; Koslowski and Schmelzer, 
2007).
    Environmental preferences for ideal foraging and reproduction 
conditions could also drive their movement. Telemetry studies of harbor 
porpoises in the Baltic region show that they concentrate in some areas 
(Read and Westgate, 1997; Teilmann et al., 2008; Sveegaard et al., 
2011). Sveegaard et al. (2011) collected satellite telemetry data to 
identify key habitat use in the Baltic region by tagging harbor 
porpoises from a Skagerrak group (northern Kattegat, Skagerrak, North 
Sea) and an Inner Danish Waters group (southern Kattegat, Belts Seas, 
western Baltic Sea). They found that harbor porpoises in the region are 
not evenly distributed, and reported nine high density areas for the 
region, with clear seasonal movement for all animals tracked. Porpoises 
from the Inner Danish Waters group move south in winter, whereas 
porpoises from the Skagerrak group move west to the North Sea; during 
the spring and summer reproductive period, the Skagerrak group stays 
close to one particular area, while the Inner Danish Waters group 
spreads out over the entire range of their distribution. No difference 
was found in home range size in relation to sex for the Inner Danish 
Waters group, but males of the Skagerrak group had larger home ranges 
than the females. A more recent abundance study by Viquerat et al. 
(2014) confirmed that harbor porpoises in the Baltic region are not 
evenly distributed and reported them to concentrate in high density 
areas.
    There is also other evidence that harbor porpoises move across 
water bodies in the Baltic region. Stable isotope analysis of prey 
items from the Baltic and Kattegat/Skagerrak Seas has shown that harbor 
porpoises move between the Baltic and Kattegat/Skagerrak Seas, although 
the magnitude of these movements is not well known (Angerbjoern et al., 
2006). An extensive review of sighting surveys and tagging has 
indicated extensive movement of animals within and between Inner Danish 
Waters and the Skagerrak/North Sea (Lockyer and Kinze, 2003).

DPS Analysis

    The petitioner did not define the geographic boundaries of its 
petitioned Baltic Sea subpopulation. Therefore, we used the best 
available data from the region to determine whether any boundaries 
exist that could be used to define a DPS within the Baltic region. Here 
we review the best available information, including information on 
physical, physiological, ecological, and behavioral factors, to 
identify a Baltic Sea subpopulation and determine whether it is a DPS, 
as defined in our Policy.
    The harbor porpoise is comprised of three subspecies in the 
northern hemisphere, which are assumed to be reproductively segregated 
by ocean basin: The North Pacific (Phocoena phocoena vomerina, Gill, 
1865), North Atlantic (P. phocoena phocoena, L., 1758), and Black Sea/
Sea of Azov (P. phocoena relicta, Abel, 1905) (Gaskin, 1984; Rosel et 
al., 1995). Within the North Atlantic subspecies, some authors have 
classified the Eastern and Western Atlantic harbor porpoises as 
populations based on migration distance (Gaskin, 1984; IWC, Sub-
Committee on Small Cetaceans, 1996). More recently, genetic studies 
also differentiate harbor porpoises from the Eastern and Western 
Atlantic (Rosel et al., 1999; Tolley et al., 2001); however, an 
analysis using mitochondrial DNA has shown that movement of harbor 
porpoises across the Atlantic does occur at a low level (Rosel et al., 
1999). Harbor porpoises in the Western Atlantic exhibit higher genetic 
diversity than those in the Eastern Atlantic (Tolley et al., 1999). 
Finer-level genetic patterns of population structure remain to be 
resolved for the Eastern Atlantic population (Tolley et al., 2004).
    The coastal nature of harbor porpoises led to an assumption of 
depth-restricted movement and a widespread acceptance of the proposal 
of thirteen populations in the North Atlantic (Tolley et al., 1999) 
(Figure 1): (1) Gulf of Maine/Bay of Fundy; (2) Gulf of St. Lawrence; 
(3) Newfoundland and Labrador; (4) West Greenland; (5) Iceland; (6) 
Faroe Islands; (7) Norway and Barents Sea; (8) North Sea; (9) Kattegat 
and adjacent waters; (10) Baltic Sea; (11) Ireland and Western British 
Isles; (12) Iberia and Bay of Biscay; and (13) Northwest Africa 
(Gaskin, 1984; Yurick and Gaskin, 1987; IWC, Sub-Committee on Small 
Cetaceans, 1996; Rosel et al., 1999; Andersen, 2003). Regional genetic 
and other studies have attempted to detail a finer subpopulation 
structure in the Eastern and Western Atlantic and test the assumption 
of the above divisions.

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[GRAPHIC] [TIFF OMITTED] TN24MR15.000

Discreteness

    Available information to inform our analysis of ``discreteness'' 
consists of genetic studies, skull measurements, contaminant profiles, 
and tooth ultrastructure. We examined the best available information in 
each of these categories to determine whether there is a set of 
individuals in the Baltic region that is discrete from the rest of the 
taxon (Figure 2).

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[GRAPHIC] [TIFF OMITTED] TN24MR15.001

Genetic Information

    Several genetic studies on the harbor porpoise have been conducted 
in the Baltic region using a wide range of methods, sampling locations, 
sample pooling, and genetic markers, which are not consistent among 
research groups. The most common genetic analyses have used 
mitochondrial DNA, followed by microsatellites, Random Amplified 
Polymorphic DNA (RAPD), and isozymes to infer genetics.
    Three studies tested for genetic divergence of individuals 
inhabiting the Baltic Sea proper, as defined by the western boundary at 
the Limhamn and Darss underwater ridges (Stensland, 1997; Wang and 
Berggren, 1997; Wiemann et al., 2010) (Figure 2). These studies did not 
find consistent support for a genetically distinct subpopulation within 
the Baltic Sea proper. For instance, Stensland (1997) found no 
significant differences between samples from the Swedish portion of the 
Baltic Sea proper and the Skagerrak when using a RAPD technique. 
Wiemann et al. (2010) used mitochondrial and microsatellite DNA to 
demonstrate a small but significant genetic separation between the 
Baltic Sea proper and the Belt Seas. However, migration rates between 
the Baltic Sea proper and adjacent Belt Seas were estimated to be high, 
at 7.5 migrants per generation. Due to low genetic divergence, and 
evidence for continued gene flow and movement, the authors admitted 
that ``it is difficult to argue in favour [sic] of a `demographic 
independency' of the Baltic Sea population.'' Overall, existing 
research is consistent in supporting low or no divergence among 
individuals from the Baltic Sea proper as compared to others in the 
Baltic region, supporting continued genetic exchange and lack of 
reproductive isolation or demographic independence. Thus, due to the 
low extent of differentiation and lack of statistical confidence in 
these results, the weight of genetic evidence does not support a 
conclusion that there is a discrete Baltic Sea proper subpopulation in 
accordance with our DPS Policy.
    Even though available genetic information did not support the 
conclusion that there is a discrete Baltic Sea proper population, a 
thorough review of available genetic information for harbor porpoises 
in the entire Baltic region revealed consistent support that 
individuals from the region are genetically differentiated from those 
individuals inhabiting the North Sea. First, all of the microsatellite 
and mitochondrial DNA methods used by Andersen (1993; Anderson et al., 
1995; Anderson et al., 1997; Anderson et al, 2001) differentiated 
samples from Inner Danish Waters (pooled sample set from the Kattegat, 
Belts, and Baltic Seas) and the North Sea. Tiedemann et al. (1996) also 
found a highly significant difference in mitochondrial haplotype 
compositions between their North Sea and Baltic Sea (pooled sample set 
from the Baltic Sea proper and Belt Seas) samples. These earlier 
studies provide consistent support that individuals in the North Sea 
have diverged from those inhabiting the waters of the Baltic region.
    The study by Wiemann et al. (2010) provides further evidence 
supporting divergence of North Sea individuals from other Baltic region 
individuals. They suggested that this genetic transition occurs in the 
Kattegat Sea, based on the most comprehensive mitochondrial and 
microsatellite DNA study on 497 harbor porpoises in the Baltic region. 
They detected overall weak population structure in the region. However, 
the population structure that was detected showed a tendency for the 
North, Skagerrak, and Kattegat Seas to cluster separately from the Belt 
and Inner Baltic Sea samples, with strong evidence for mixture of 
genetic lineages throughout the region. The transition zone in the 
Kattegat Sea area was supported by an abrupt shift in haplotype 
composition; one particular haplotype that is almost absent in the

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North Sea was the most abundant in the Belt Sea and Inner Baltic Sea. 
Furthermore, mitochondrial DNA pairwise comparisons of genetic 
divergence among Skagerrak and Kattegat samples showed significant 
divergence between them, indicating that the genetic split likely 
occurs somewhere within the Kattegat Sea. This study obtained generally 
strong agreement between independent data from microsatellite and 
mitochondrial haplotypes, providing robust support for this genetic 
transition zone in the Kattegat Sea.
    Based on the best available genetic data, there is evidence that 
the harbor porpoise is weakly diverged between the North Sea and the 
Baltic region past Kattegat and south/eastward into the Baltic Sea.

Skull Comparison Information

    Skull comparisons of harbor porpoises in the Baltic Region have 
also been used to explore morphological evidence for population 
structure. The weight of available skull information aligns with 
genetic information in that it differentiates North Sea harbor 
porpoises of both sexes from those in the Baltic region. A finer 
population structure is seen for females within the Baltic region, but 
this same skull differentiation is not seen in males.
    Skull studies support the genetic information indicating a genetic 
break, or transition zone, between the North Sea and the Baltic region. 
Non-metric (not measured) skull characters of harbor porpoises from the 
North Sea and Baltic Sea are found to differ (both sexes; Kinze 1990, 
Huggenberger et al. 2000). In addition, harbor porpoise skull 
measurements are different between the North Sea and Baltic Sea (both 
sexes; Kinze, 1985, 1990; Borjesson and Berggren, 1997; Huggenberger et 
al., 2000; Galatius et al., 2012).
    Some skull studies achieved a finer-scale geographic resolution of 
harbor porpoises in the Baltic region. However, the statistical results 
of these studies are more robust in females than in males, suggesting 
male migration and mixing between areas (Huggenberger et al., 2002). 
Borjesson and Berggren (1997) examined harbor porpoise skulls from the 
Baltic Sea proper and the Kattegat and Skagerrak Seas and their 
statistical analyses showed geographically-relevant differences in 
skull characters between females from the Baltic Sea proper and the 
Kattegat and Skagerrak Seas, but not the same for males; five of 16 
skull characters were significantly different in female samples, 
whereas one of 16 skull characters significantly differed in male 
samples.
    Galatius et al. (2012) used geometric morphometric skull 
comparisons (70 cranial landmarks registered with a 3-D digitizer) from 
six geographic areas--the North Sea, Skagerrak Sea, Kattegat Sea, Belt 
Seas, western Baltic, and Inner Baltic Sea and found highly significant 
shape differences in skulls among these six geographic areas. There 
were no significant differences between males and females or sampling 
seasons within any of the samples. Their results indicate a 
morphometric segregation of harbor porpoises within the Belt Seas/Inner 
Baltic Sea. However, this study stands alone in differentiating this 
fine population structuring within the Baltic region, as the weight of 
genetic and other skull information does not support the same 
conclusion.
    The weight of available skull information aligns with genetic 
information in that it differentiates North Sea harbor porpoises of 
both sexes from those in the Baltic region. Available skull information 
provides evidence of a finer population structure within the Baltic 
region for females, but not for males. This difference provides 
evidence of exchange of male, but not female, individuals between and 
among the Baltic region and the North Sea. One skull study was able to 
detail a fine population structure for both sexes within the Baltic 
region, but the weight of other available evidence does not support 
such a conclusion.

Contaminant Profile Information

    A few studies have distinguished North Sea or Skagerrak harbor 
porpoises from the rest of the Baltic region based on contaminant 
levels and patterns. Bruhn et al. (1997; 1999) analyzed blubber samples 
in harbor porpoises from the German North Sea, Baltic Sea proper, and 
off the west coast of Greenland. Clear differences existed between the 
Baltic Sea proper and North Sea animals for certain contaminants. 
Berggren et al. (1999) found that mature males in the Swedish part of 
the Baltic Sea had significantly different contamination patterns of 
polychlorinated biphenyls (PCBs) than animals from the Swedish Kattegat 
and Skagerrak coasts and from western Norway. This information is 
consistent with genetic information to show population differences 
between the North Sea and Baltic region.

Tooth Ultrastructure Information

    Tooth ultrastructure in the harbor porpoise has been examined to 
differentiate between porpoises from different regions. Lockyer (1999) 
found different characteristics in tooth layers, which may be genetic 
in origin or influenced by life history events or other factors. The 
author found significant differences in several tooth characteristics 
between the North Sea, Skagerrak Sea, Kattegat Sea, Inner Danish 
waters, and the Baltic Sea proper. Lockyer (1999) stated the use of 
tooth ultrastructure alone ``is not sufficient to allow an individual 
animal to be assigned to a particular management unit.'' Thus, her 
results are not informative alone and should be combined with other 
studies when helping to delineate a population structure. The tooth 
ultrastructure study does not align with genetic and other information, 
since it differentiates a finer scale than is supported by the weight 
of available information. Therefore, we do not find this information 
persuasive.

Conclusion Regarding Discreteness

    After combining the weight of evidence from genetic, skull, 
contaminant, and tooth studies we conclude that there is a discrete 
subpopulation of harbor porpoises in the Baltic region (from the 
Kattegat Sea, at the genetic break found by Wiemann et al. (2010), 
eastward into and including the Baltic Sea proper). Although there are 
shared haplotypes among harbor porpoises in the Baltic region and 
evidence of some male movement to suggest that a certain level of gene 
flow exists within the Baltic region, the repeated evidence of 
statistically significant genetic divergence from North Sea/Skagerrak 
samples guides our conclusion that this can be considered a discrete 
subpopulation. Available information on skull measurements and 
contaminant studies supports our conclusion based on genetic 
information, since these studies also differentiate North Sea/Skagerrak 
harbor porpoises from those in the Baltic region. Lockyer's (1999) 
study differentiated tooth structure among harbor porpoises from the 
North Sea, Skagerrak, Kattegat, Inner Danish waters, and the Baltic 
Sea; however, she caveats that this must be combined with other 
supporting information, and we did not find that the weight of other 
available information supports her proposed population structure. The 
weight of all evidence favors our conclusion of a population split at 
the Kattegat Sea.
    Since we determined that there is a discrete Baltic region 
subpopulation, we next determine whether the discrete population is 
significant to the taxon. From this point forward in the document, we 
define the Baltic harbor porpoise subpopulation as beginning at

[[Page 15563]]

the Kattegat inward (south/east) to and including the Baltic Sea 
proper.

Significance

    The identified discrete Baltic subpopulation does not persist in an 
ecological setting unusual or unique for the taxon. Differences seen in 
harbor porpoise morphological characteristics (skull and tooth 
analyses) may be related to differences in environment, but available 
information is not informative enough at this point to link these 
characteristics to distinct habitats or specific adaptations at 
present. The habitat utilization reported for the Baltic harbor 
porpoise does not differ from general descriptions of the species' 
habitat preference. They are found in the shallow coastal areas of the 
Baltic region and their preference for shallow water calving and 
nursing does not differ from the general preference of the species. The 
opportunistic feeding nature of the Baltic harbor porpoise also does 
not show it to persist in a unique ecological setting. They target high 
lipid content fish to fulfill large energetic requirements, similar to 
the general preference of the species.
    There are insufficient data to conclude that loss of the identified 
discrete Baltic subpopulation would result in a significant gap in the 
range of the taxon. The Baltic subpopulation comprises only a small 
geographic area in the total range of the species and even the 
subspecies. There are purported to be around ten other subpopulations 
in the North Atlantic (Tolley et al., 1999) and other harbor porpoise 
populations in the North Pacific and Black Sea. Additionally, available 
information reveals movement and some level of gene flow throughout the 
Baltic region through evidence of shared haplotypes, which is discussed 
further below. Although there are caveats to determining the exact 
level of mixing between the North Sea and Baltic region (and vice 
versa), there is evidence to show at least some level of mixing, such 
that a loss of the Baltic subpopulation would not lead to a significant 
gap in the range of the taxon. There is evidence of continued admixture 
and gene flow between these regions. This gene flow may be sustained by 
the high dispersal capacity and movement of these animals, and the lack 
of obvious physical barriers between the regions.
    While multiple studies confirm divergence between individuals from 
the North Sea and those inhabiting the Baltic region past the Kattegat 
Sea, the absolute extent of divergence is consistently weak. For 
instance, all analyses of mitochondrial haplotype distribution have 
revealed shared haplotypes throughout the region, even across the 
Kattegat `transition zone' (Tiedemann et al., 1996; Wang and Berggren, 
1997; Wiemann et al., 2010). In Wiemann et al. (2010), an abrupt shift 
in microsatellite haplotype distribution was observed between the North 
Sea and Baltic region past the Kattegat Sea, but the two most abundant 
haplotypes only differ by a single point mutation. No physical barrier 
exists between the Kattegat and the North Sea, porpoises are known to 
move long distances (Teilmann et al., 2009), and evidence suggests that 
genetic connectivity can occur among harbor porpoises separated 
thousands of kilometers in the North Atlantic (Tolley et al., 1999; 
Fontaine et al., 2007). So, while the weak divergence (separating the 
North Sea from the Baltic region) is well supported, continued genetic 
exchange, connectivity, and ongoing reproduction among animals 
throughout the region is likely.
    There is no evidence that the identified discrete Baltic 
subpopulation represents the only surviving natural occurrence of a 
taxon that may be more abundant elsewhere as an introduced population 
outside its historical range. Harbor porpoises are historically 
widespread in the northern hemisphere. As stated previously, within the 
North Atlantic subspecies, genetic studies differentiate harbor 
porpoises between the Eastern and Western Atlantic, with some level of 
mixing. The Baltic subpopulation does not represent the only surviving 
natural occurrence of a taxon that may be more abundant elsewhere as an 
introduced population outside its historical range, as there are 
clearly many other existing natural populations.
    There is no evidence that the identified discrete Baltic population 
differs markedly from other populations of the species in its genetic 
characteristics. The attachment of skull characters to unique 
environments or conditions would show evidence of adaptive genetic 
characteristics; however, the available harbor porpoise skull 
information from the Baltic region does not definitively attach 
characters to environmental connections to show that any skull 
differences are adaptive. One harbor porpoise skull study suggests that 
skull morphology could be attached to particular environments or 
conditions (Galatius et al., 2012). However, this is not supported by 
the weight of genetic evidence and is not even supported by other skull 
analyses, as they did not test adaptive skull characteristics and 
attach them to local or unique environmental conditions in the Baltic 
region. In addition, we did not find much discussion in the available 
literature about how differences in skull character for harbor 
porpoises may relate to adaptation to a particular prey item. Most of 
these skull studies attempt to delineate a population structure without 
testing the attachment of particular skull distinctions or 
characteristics.

Conclusion Regarding Significance

    In conclusion, we find that the Baltic harbor porpoise 
subpopulation, while it may be discrete, does not meet any factors 
under the significance criterion. As such, we conclude that the Baltic 
harbor porpoise subpopulation is not a DPS as defined by our joint DPS 
Policy.

Finding

    We find that the Baltic harbor porpoise subpopulation does not meet 
the DPS Policy criteria for qualifying as a DPS. Therefore, listing the 
petitioned entity under the ESA is not warranted.

References Cited

    A complete list of all references cited in this notice can be found 
on our Web site and is available upon request (see ADDRESSES).

Authority

    The authority for this action is the Endangered Species Act of 
1973, as amended (16 U.S.C. 1531 et seq.).

    Dated: March 18, 2015.
Samuel D. Rauch, III,
Deputy Assistant Administrator for Regulatory Programs, National Marine 
Fisheries Service.
[FR Doc. 2015-06749 Filed 3-23-15; 8:45 am]
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