Fish
Fish were sampled using throw nets and lift nets. Not enough water made its way onto the marsh above Rt 146, therefore marsh surface sampling above the gates was not feasible. Instead the main channels were sampled using throw nets. Three permanent sampling stations were established between The North Marsh and Rt 146 (triangles on Fig 13). Each station was sampled three times during each sample date by randomly tossing the throw net into the channel and collecting all fish. Lift nets were placed on the marsh surface near the transects downstream of Rt 146 (circles on Fig. 13). One was established in extreme low marsh just above mean low water, a second was placed at the mid low marsh elevations and a third was situated at the upper end of the low marsh just below a salt meadow cordgrass zone. All fish sampling was conducted monthly on spring tides between April and October as close to high slack water as possible. Fish were identified and measured before being returned to the channel.

Results of the fish sampling are shown in Table 8 Densities (#/m2) varied from month to month depending on the species. For example, in the restricted marsh channels the density (number of individuals per square meter of sample) of grass shrimp (Palaemonetes pugio ) was 304 in May, 44 in June, 2 in July, 340 in August and 112 in September. Although the density of mummichogs (Fundulus heteroclitus) also varied by month, their numbers suggest a pattern. For instance, mummichog densities in the restricted marsh was 4 in June and 208 in July. The differences between the two months were the high numbers of juvenile fish caught in July (Tables 9, 10 & 11). This may suggest a preference by the young mummichogs for the relative safety of the restricted marsh habitat (larger predators appear to not be entering the partially opened tide gate).

Table 8. Summary of fish collection data for the four primary species by month between the restricted and unrestricted portions of the marsh system. Data refers to combined totals for all samples taken within the sampling period. Restricted marsh based on throw nets at three stations at high tide; unrestricted marsh based on lift nets at three stations at high tide. Some of the differences in denstities between the two sites may be due to the variations between the sampling technique utilized here. % Abundance refers to the total number of individuals of a particular species divided by the total number of all fish from all stations on the sampling date.

Month	Species	% Abundance in:	Density (# / m2) in:
ff	ff	restricted / unrestricted	restricted / unrestricted
May	Fundulus heteroclitus	2 / 25	7 / 0.7
ff	Palaemonetes pugio	97 / 62	304 / 2
ff	Fundulus majalis	0 / 12	0 / 0.3
ff	Menidia menidia	0 / 0	0 / 0
June	Fundulus heteroclitus	9 / 10	4 / 0.8
ff	Palaemonetes pugio	89 / 90	44 / 7
ff	Fundulus majalis	0 / 0	0 / 0
ff	Menidia menidia	0 / 0	0 / 0
July	Fundulus heteroclitus	96 / 9	208 / 1
ff	Palaemonetes pugio	1 / 58	2 / 7
ff	Fundulus majalis	1 / 9	1 / 1
ff	Menidia menidia	0.4 / 22	3 / 2
August	Fundulus heteroclitus	9 / 7	36 / 2
ff	Palaemonetes pugio	89 / 91	340 / 30
ff	Fundulus majalis	0.3 / 0.5	1 / 0.2
ff	Menidia menidia	1 / 1	2 / 0.3
Sept	Fundulus heteroclitus	1 / 10	1 / 0.2
ff	Palaemonetes pugio	98 / 90	112 / 1.5
ff	Fundulus majalis	0 / 0	0 / 0
ff	Menidia menidia	1 / 0	1 / 0

Table 9. Length measurements for Fundulus heteroclitus. Length of fish was measured from the tip of the nose to the beginning of the caudal fin. Total number of fish are shown in parentheses.

Month	Species	Range in Length (cm)	Average Length (cm)
ff		restricted / unrestricted	restricted / unrestricted
May	F. heteroclitus	3.0 - 5.0 / 4.0 - 9.2	4.0 (21) / 6.0 (4)
June	F. heteroclitus	2.5 - 5.5 / 2.1 - 6.5	4.0 (20) / 5.0 (5)
July	F. heteroclitus	1.5 - 6.0 / 1.3 - 6.2	3.4 (467) / 2.4 (6)
August	F. heteroclitus	2.0 - 5.5 / 1.0 - 7.4	3.3 (81) / 2.4 (14)
September	F. heteroclitus	4.0 - 4.5 / 8.4	4.3 (2) / 8.4 (1)

Table 10. Average length (cm) of Fundulus heteroclitus by sample by station by month in the restricted marsh. Station #1 is furthest upstream; Station #2 lies midway; Station #3 at convergence of two main channels about 100 meters above the tide gates. Total number of fish are shown in parentheses.

Month	Station #1	Station #2	Station #3	Avg
ff	1 / 2 / 3	1 / 2 / 3	1 / 2 / 3	ff
May	4.5 / 3.7 / 3.5	4.3 / x / x	x / x / x	4.0
ff	(10) / (8) / (1)	(2) / x / x	x / x / x	ff
June	4.0 / 3.0 / 3.5	x / x / 4.7	x / 4.0 / 4.5	4.0
ff	(6) / (2) / (4)	x / x / (10)	x / (6) / (2)	ff
July	1.8 / 2.1 / 2.5	3.2 / 3.0 / 2.9	5.1 / 4.8 / 5.2	3.4
ff	(6) / (279) / (131)	(12) / (10) / (7)	(5) / (8) / (9)	ff
August	3.0 / 3.0 / 3.3	3.0 / 3.0 / 3.0	4.0 / 3.8 / 3.8	3.3
ff	(21) / (24) / (15)	(1) / (2) / (2)	(3) / (5) / (8)	ff
September	4.5 / x / 4.0	x / x / x	x / x / x	4.3
ff	(1) / x / (1)	x / x / x	x / x / x	ff

Table 11. Average length (cm) of Fundulus heteroclitus by Lift Net station by month in the unrestricted marsh. Station #1 is lowest elevation; Station #2 lies midway; Station #3 at high marsh border. Total number of fish are shown in parentheses.

 

Month	Lift Net Station #1	Lift Net Station #2	Lift Net Station #3	Avg
May	6.2 (1)	6.0 (3)	x	6.0
June	5.5 (1)	2.1 (1)	5.7 (3)	5.0
July	x	x	2.4 (6)	2.4
August	x	1.6 (9)	4.0 (5)	2.4
September	8.4 (1)	x	x	8.4

The total number of species of fish and shrimp caught in the restricted marsh was 7 and in the unrestricted marsh, 6. Differences between the two portions of the system included the presence of shad in the unrestricted marsh and the occurrence of sticklebacks in the restricted marsh.

Table 8 also lists the percent abundance of the major fish species collected. An interesting result of the fish sampling is the similarities between the two portions of the system in percent abundance. For example, the percent abundance of mummichogs and grass shrimp caught in the restricted versus unrestricted marsh areas in June (9% vs. 10% and 89% vs. 90%), August (9% vs. 7% and 89% vs 91%) and to a lesser extent, September (1% vs. 10% and 98% vs. 90%) were relatively even. This data suggests that, at least in portions of the year, that the same mix of species are using the marsh surface in the unrestricted marsh as the tidal channels in the restricted marsh. Although there was no correlation between the sites in May (2% vs. 25% and 97% vs. 63%) and July (96% vs. 9% and 1% vs. 58%), the July data also includes a high number of young fish that may be utilizing the relative safety of the restricted marsh.

Fish (caught or observed)
American Eel (Anguilla rostrata)
American Shad (Alosa sapidissima)
Atlantic Silversides (Menidia menidia)
Blue-Back Herring (Alosa aestivalis)
Four-Spine Stickleback (Apeltes quadracus)
Mummichog (Fundulus heteroclitus)
Northern Pipefish (Syngnathus fuscus)
Sheepshead Minnow (Cyprinodon variegatus)
Striped Killifish (Fundulus majalis)
Summer Flounder (Paralichthys oblongus)
Tautog (young) (Tautoga onitis)
Three-Spine Stickleback (Gasterosteus aculeatus)
Weakfish (Cynoscion regalis)

 

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