Able et al Distribution, movements, and habitat use of small Morone saxalilis across multiple spatial scales 
189 
sources (e.g., food, benign environmental conditions) 
are likely causes (e.g., Mather et al., 2009). Further, 
the long duration of their stay in a non-natal estuary 
enhances the possibility of learning behavior at a young 
age that may lead to contingent formation (Secor, 1999). 
Distribution and habitat use in a non-natal estuary 
Once small striped bass dispersed into the estuary at 
Mullica River-Great Bay, regardless of the source of 
these individuals, a large proportion of them took up 
residence there for months. Their residency is evident by 
their presence in the system during all seasons (Table 
2, Fig. 7). During this time they were most frequently 
observed in the Mullica River but less frequently in 
Great Bay. This is a very different pattern from that of 
the larger juveniles and adults who are typically pres- 
ent only seasonally in this estuary, particularly during 
the spring and fall (Able and Grothues, 2007; Grothues 
et al., 2009). It is consistent with the interpretations of 
coastal migrations by the larger and older individuals 
through non-natal estuaries, as also occurs in Mas- 
sachusetts (Mather et al., 2009; Pautzke et al., 2010). 
As a result of our analysis, based on multiple spatial 
scales and multiple techniques, it seems clear that the 
Mullica River-Great Bay estuary, and probably other 
non-natal estuaries in the Middle Atlantic Bight, are 
commonly used by small striped bass that disperse 
from natal estuaries and take up residence in this and 
other non-natal estuaries (Able and Fahay, 2010). Thus, 
should these non-natal estuaries be considered nurser- 
ies? A reevaluation of the nursery concept (Beck et al., 
2001) and subsequent dialogue (Dahlgren et al., 2006; 
Sheaves et al., 2006; Fodrie et al., 2009) clarify several 
points regarding this question. First, we do not know 
whether the pattern of dispersal to and colonization 
of the non-natal Mullica River-Great Bay estuary is 
common to other non-natal estuaries and whether this 
colonization is accomplished by immature or maturing 
individuals. Second, if colonization does occur com- 
monly, we do not know the degree of the contribution 
of these individuals to adult reproduction or population 
growth, in part, because there are so few studies of the 
dispersal of young striped bass (< 20 cm), or any spe- 
cies, out of estuaries (Deegan, 1993; Beck et al., 2001; 
Gillanders et al., 2003). Third, it should not be sur- 
prising that a mosaic of habitats (e.g.. Sheaves, 2005; 
Sheaves et al., 2006), including non-natal estuaries, is 
used by striped bass, and other species (Gillanders et 
al., 2003; Dahlgren et a!., 2006) and the complexity 
of the mosaic may influence population growth (e.g., 
Fodrie et al., 2009) and add to a population’s buffering 
capacity against unfavorable habitat dynamics (e.g., 
Secor, 2007). One possible solution is to consider natal 
estuaries, and their subsequent use by young-of-the- 
year and small juveniles, as primary nurseries and 
non-natal estuaries as secondary nurseries for slightly 
older individuals. This approach has been useful in 
identifying shark nurseries (Bass, 1978; Merson and 
Pratt, 2007). 
Egress from a non-natal estuary 
It appears that small striped bass leave non-natal estu- 
aries, such as the Mullica River-Great Bay system, to 
begin coastal migrations at the same sizes as those in 
natal estuaries. This departure of juveniles to become 
coastal migrants may vary after months, to perhaps 
years, of residency. Others have suggested that move- 
ment from natal estuaries to join the coastal migration 
may be size or age related such that juveniles may begin 
to leave estuaries after two years (Merriman, 1941; 
Kohlenstein, 1981; Setzler-Hamilton and Hall, 1991; 
Secor and Piccoli, 1996; Zlokovitz et al., 2003). It is 
known that egress from Chesapeake Bay by immature 
females occurs in early spring at age 2 and 3 (Mer- 
riman, 1941). These patterns are consistent with the 
occurrence of striped bass of similar sizes along the 
coast determined by tag-recapture of striped bass in the 
ALS tagging program. For instance, a majority of fish 
recaptured along the coast of New Jersey after release 
in natal estuaries were larger individuals (>40 cm TL) 
that may be joining the annual coastal migration. These 
larger individuals were also frequently recaptured in 
presumably non-natal habitats in the Gulf of Maine and 
along the coasts of Connecticut and Rhode Island after 
initial release in New Jersey waters. This same pattern 
has been reported for age 2 and 3 fish moving into non- 
natal estuaries, such as the Connecticut River (Kynard 
and Warner, 1987) and in Massachusetts where 40-50 
cm TL individuals (most age 2-5) apparently feed during 
the summer, make coastal migrations during the fall 
through spring, but return in subsequent years (Mather 
et al., 2009, 2010; Pautzke et al., 2010). Certainly, other 
estuarine-dependent fish species leave estuaries when 
they reach a size threshold (Rountree and Able, 1992; 
Potter et ah, 1997). This pattern for striped bass may 
vary with sex, i.e., females are likely to leave at earlier 
ages or smaller sizes, whereas males tend to remain, at 
least in natal estuaries, for longer periods of time (Secor 
and Piccoli, 1996). 
In general, overall patterns of use of a non-natal estu- 
ary and scheduling of departure appear similar between 
natal and non-natal estuaries and we also suspect that 
there are no major changes in these patterns before 
and after the recovery of the striped bass population 
in recent years (Boreman and Lewis, 1987). However, 
we hasten to point out that there was little emphasis 
on non-natal estuaries as secondary nursery habitat 
before the recovery. 
Conclusion 
As we have demonstrated, non-natal estuaries are 
potentially important habitat for small (20-46 cm) 
striped bass. This finding may further complicate our 
understanding of life cycle diversity (see Secor and 
Kerr, 2009) for this species because the prior focus has 
been on natal estuaries. Further, as these individu- 
als from non-natal estuaries join the annual coastal 
