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Long-term population trends in American lobster (Homarus americanus) and their relation to temperature in Long Island Sound.

ABSTRACT Existing long-term monitoring data and studies initiated in response to the 1999 lobster die-off in Long Island Sound were examined to determine long-term trends that might clarify causes of the die-off. Data examined included a 28-y time series of commercial lobster-trap catch (harvest and discard) sea-sampling, a 20-y time series of research trawl survey indices, a 13-y time series of bottom water temperature, 3 y of mark-recapture data and 1 y of a research trap survey. Movement information was gathered from the recapture of 2,309 lobsters at large within the Sound for more than 30 days (average days at large = 177). Only 9% of the recaptured lobsters traveled more than 10 km from their release point and 1.3% traveled more than 20 kin. Based on the recaptures reported over 3 y, it appears that most lobsters remain resident in the Sound and do not travel extensive distances. The eastern portion of Long Island Sound contained the majority of lobsters that moved greater distances. Abundance of lobsters by size class taken in the trawl survey showed a rise in overall abundance during the 1990s due to a substantial increase in the abundance of pre-recruit and recruit size lobsters (<82 mm CL). Following the die-off, abundance of all size classes declined sharply. The increase and decrease in abundance of the sublegal size classes were negatively correlated with mean summer bottom water temperature. Following the die-off, the percentage of females that were egg-bearing in catches from the western Narrows, the area hardest hit by the die-off, was significantly lower compared with the rest of the Sound. It appears that egg-beating females were most vulnerable to mortality factors causing the die-off, and/or these factors may have limited their ability to carry eggs. Observed mortality in the commercial catch in the western Sound also correlated with mean summer bottom water temperature over 8 y bridging the die-off (1996-2003). Multiple factors probably played a role in the higher-than-normal mortality recorded in 1999, however, the long-term monitoring data examined here implicate increased bottom water temperatures as a significant contributing factor.

KEY WORDS: lobster, Homarus americanus, population trends, movement, temperature effects (mortality)


The American lobster (Homarus americanus H. Milne Edwards, 1837) supports a valuable and intensive commercial fishery in Long Island Sound (LIS), rivaling the dockside value of subsidized shellfish harvested from leased beds. Lobster landings from the Sound rose steadily for two decades, peaking in 1996 to 1997 when Connecticut and New York landed approximately l 1 million pounds with an ex-vessel value of approximately $42 million (Blake 1998, CT DEP 2000, NOAA 2004). Historically, 50% to 60% of this harvest occurred in western Sound waters. The massive die-off that began in the fall of 1998 and intensified in 1999 impacted these productive waters. In the westernmost reaches of the Sound, known as the Narrows, landings fell 42% to 99% in one season. The condition of the western Sound fishery continued to deteriorate in the following 4 yr (2000-2003).

The purpose of this study is to support research into the causes of the die-off by understanding the breadth of the problem geographically and over time. The approach used was analysis of existing long-term monitoring data in comparison to studies initiated in response to the die-off. These data also can be used to evaluate the likelihood of stock recovery.


Existing monitoring data come from 2 sources: sea-sampling of the commercial lobster trap fishery (harvest and discard) as fisheries dependent data and fisheries independent data. Independent data include stratified random trawl survey indices, a research trap survey and water quality data. Mark-recapture data were gathered from the fishery and independently. The time series available for fisheries dependent data is 1996 to 2003, with intermittent data for 1976 to 1995. The time series available for trawl survey seasonal abundance indices is 1984 to 2003. Weekly data for the trap survey is available for 2003. Monthly water-quality data are available for 1991 to 2003 from the CT DEP Water Quality Monitoring Program for Long Island Sound axial stations (Lyman & Simpson 2002). Lobster mark-recapture data are available for 2001 to 2004.

Long Island Sound Trawl Survey

Lobsters were sampled independent of the fishery by otter trawl during cruises conducted by the CT DEP Long Island Sound Trawl Survey (LISTS, Gottschall & Pacileo 2002). This survey uses a 14-m sweep trawl towed at 3.5 kts for 30 min from a research vessel. Stations were sampled from all trawlable LIS waters between New London and Norwalk, CT (Fig. 1) based on a stratified random design with 4 depth strata (0-9 m, 9.1-18.2 m, 18.3-27.3 m, 27.4 + m) and 3 bottom substrate strata (sand, mud and transitional). Except for 4 y (Table 1), survey data used in this analysis came from at least 40 stations sampled monthly during spring (April, May, June) and fall (September and October), totaling 200 tows annually. In fall 2003, October sampling was delayed until November due to vessel repairs. Potential bias due to the late sampling in 2003 was examined by analysis of variance of October and November catch rates of lobster in 1985 to 1990, years when LISTS samples were routinely taken in both months. Analysis of variance showed that there was no significant difference between catches in the 2 mo over the 6 y (Oct mean = 4.8, Nov mean = 6.8, DF = 479, P = 0.08). Therefore, all samples taken in 2003 were used for the fall index.


All lobsters collected in each tow were counted and a composite weight was recorded ([+ or -] 0.1 kg). Biological data were recorded for all lobsters, or a minimum of 50 when measuring the entire catch was not possible. Data recorded included condition (alive/dead), carapace length (CL) to 1.0 mm, sex and presence of eggs.

Beginning in 2000, additional trawl survey tows were made in the Narrows of the western Sound (Fig. 1) for comparison to LISTS indices. Six fixed sites, from Stamford, Connecticut to Hempstead, New York, were sampled monthly in the same manner as the LISTS. Sampling six sites within the Narrows resulted in a sampling intensity of approximately one site per 41 [km.sup.2], compared with one per 68 [km.sup.2] in the rest of the Sound (LISTS).

Both arithmetic and geometric means were calculated for the number of lobsters caught in each survey tow. Catch from tows shorter than 30 min was expanded to an equivalent 30-min catch. The arithmetic mean was computed as the most familiar measure of central tendency, however, it can be skewed by tows with extraordinarily large numbers of lobsters. The geometric mean, computed using natural log values, is a more reliable measure of relative abundance. Delta means were calculated for the catch per tow of specific size classes by sex, including egg-beating and non-egg-beating females, because of the high number of zero-catches for each class (Aitchison & Brown 1957). Three size classes were identified with lengths that varied slightly with regulation changes: legal, 1984 to 1988 >80.9 mm CL, 1989 >81.7 mm CL, 1990 to 2003 >82.5 mm CL; recruit, the interval within approximately 10 mm CL of legal size which corresponds to the size range one molt below legal length; and prerecruit, 1984 to 1988 <71 mm CL, 1989 <72 mm CL, 1990 to 2003 <73 mm CL. Few lobsters smaller than 40 mm CL were captured in the survey net.

Lobsters were captured for tagging in trawl catches made during the LISTS and from commercial lobster vessels during seasampling trips from August 2001 through April 2004. In 2002 to 2003, tagging was suspended from mid-July to September due to high mortality associated with high water temperatures. Lobsters were tagged with T-Bar anchor tags. Tagging methods and laboratory studies examining tag-induced mortality and temperature effects are described in detail in Simpson et al. (2003). Most lobsters were tagged on commercial vessels and were immediately released at the location of capture. Lobsters that were tagged onboard the research trawl survey were usually released in batches within the same sampling grid (Fig. 1). Both capture and release locations were recorded on a shipboard or handheld global positioning system (GPS) recorder. Long Island Sound was divided into five geographic zones based on prior catch patterns (Fig. 2A). In each zone the annual target was 100-200 lobsters tagged for each of six groups: 3 size groups (legal >82.6 mm CL, recruit 72 to <82.6 mm CL, and prerecruit 60 to <72 mm CL), and for males, nonegg-bearing females and egg-bearing females. Lobsters <60 mm CL have a lower likelihood of being recaptured in pots and therefore were not tagged.


Recapture information was obtained from commercial and recreational fishers and from LISTS catches. A 2-tiered tag recapture reward system was used to enhance and evaluate recapture rates. The standard tag was orange and carried a reward of $5. This reward was given for the information returned (not the tag); fishers were asked to return both legal and sublegal tagged lobsters to the water to maximize information from multiple recaptures of individual lobsters. High reward white tags worth $100 each were deployed at a rate of one to every 50 to 100 orange tags. The ratio of return rates for these high value tags to the initial recapture of standard tags was used as a measure of cooperation for the standard $5 tags. To further enhance reporting rates, a subset of 99 orange-tag returns selected at random each year had a $100 reward and one had a $1,000 reward. All license holders in Connecticut and New York were mailed two notices describing the tagging study, including a postage-paid form to record recapture information. Distance moved (net movement) was calculated as the straight line distance between the initial release point and the final recapture point.

Western Long Island Sound Lobster Trap Survey

A fishery independent lobster trap survey was conducted .in western Long Island Sound during 2003 (WLISTS, McKown et al. 2004). Seventy-five five-trap trawls (375 traps total) were set in three transects across western Long Island Sound (Fig. 3). Traps were sampled and reset weekly from June to November. Frozen menhaden (Brevoortia tyrannus) was used as bait. All species caught were identified and counted, lobsters measured, and egg-bearing status determined as described earlier for the trawl survey (LISTS).


Fisheries Dependent Data

The commercial catch of lobster was measured by sea samplers who accompanied commercial fishers aboard their vessels. Sampling was designed to take place on a year-round basis, as long as cooperators were available and willing to take staff on their vessels. During 1976, a total of 91 sea-sampling trips were made on Connecticut fishing vessels in a monthly distribution across the eastern, central and western basins of the Sound in proportion to the magnitude of landings (Smith 1977). From 1982 to 2000, sampling effort on Connecticut vessels was distributed in proportion to landings but at a lower sampling intensity. Total trips ranged from 6 to 36 annually. Sampling intensity was increased again in 2001 to 2002 (total annual trips 73 and 77, respectively), and reduced to 41 in 2003. Sea sampling trips with New York fishers ranged from 6 to 12 trips annually from 1984 to 1991, and then intensity increased during 1992 to 1994 particularly in western LIS (33-57 trips annually). Sampling decreased to low levels in 1995 to 1998 (no sampling occurred during 1997), and increased again in 1999 to 2002 (21-37 trips annually); however, only four trips were made in 2003. Data recorded were identical to that described above for LISTS sampling. During each trip an attempt was made to measure all lobsters captured, but in cases of very large catches subsampling was necessary so as not to disrupt the normal operations of the vessel.


Mark-recapture Study

A total of 13,437 lobsters were tagged and released in LIS and waters surrounding the Race, a deepwater boundary between Long Island Sound and Block Island Sound. Approximately three-quarters (9,976 lobsters or 74%) were tagged on commercial vessels and the remainder (3,461 lobsters or 26%) were tagged on the research trawl survey. Recaptures that were tagged from commercial vessels (1,503 lobsters or 87%) were the majority of tags returned by commercial fishermen. The remaining 13% of recaptured lobsters had been released from the CT DEP research vessel. Only four lobsters were recaptured by the CT DEP vessel during LIST surveys. The overall reporting rate by Connecticut fishers was computed by comparing the return of high reward and standard tags. The resulting value of 48% indicated that approximately half of all tags encountered were actually returned.

Movement information from release point to each recapture point (Table 2) was gathered for 1,729 lobsters at large within the Sound more than 30 days (average days at large = 177). Multiple recaptures were common: 30% of recaptured lobsters were recaptured more than once; 11% were recaptured more than twice and up to seven times. From August 2001 through February 2004, movement for the majority of recaptures (1,290 of 1,729 or 75%) was 5 km or less (mean = 3.68 km). Only 9% of recaptures showed lobsters traveling more than 10 km from their release point and only 1.3% traveled more than 20 km. When movement was examined by zone of release, mean distance traveled for all groups (size and gender) was still less than 10 km. Movement across tagging zones was recorded for 113 (6.6%) of 1,706 tagged lobsters with reliable recapture information and at large 30 days or more. Few of these lobsters traveled across halves of the western basin (zones 1 and 2) or central basin (zones 3 and 4), and movement of these few was both eastward and westward (Fig. 2B). Forty-two lobsters (2.5%) moved between the western and central basins (zones 1-2 and 3-4), with 33 of the 42 traveling east. Only seven lobsters moved between the central and eastern basins and three lobsters tagged near the Race were recaptured in Rhode Island/Block Island waters.

Survey Abundance and Stock Composition

LISTS abundance indices for spring and fall were steady for the first 5 y, 1984 to 1989 (Table 1, Fig. 4), and then rose significantly until 1999. The indices declined just as significantly from 2000 to 2002. The LIST index for fall 2002 was the lowest in the 20-y time series (1984-2003). The LIST index for spring declined again in 2003, ranking 15th out of 20, however the LIST index for fall 2003 showed the first increase since 1999, ranking 17th out of 20.


Abundance by size class taken in the LISTS over the time series shows that the rise in overall abundance during the 1990s can be attributed to a substantial increase in the abundance of prerecruit and recruit size lobsters (<82 mm CL). This marked increase of smaller lobsters was most obvious in the spring (Fig. 5A), but was also seen in the fall time series (Fig. 5B). This period of good recruitment ended in 1999 to 2000. The pattern in prerecruit and recruit abundance for females showed a negative correlation with average summer bottom water temperatures from 1991 to 2003 (DF = 11, r = -0.55 to -0.65, P < 0.053, Fig. 6 and Fig. 7A and B). Males in these size classes also showed a negative trend with water temperature, but the relationship had less statistical strength (DF = 11, r = -0.50 to -0.52, P < 0.083, Fig. 7A and B).


Abundance indices in the Narrows did not vary from indices computed from the standard LISTS area immediately following the die-off (Fig. 8) and abundance in both areas declined in the following 3 y. However, the composition of the lobster catch varied between the two areas over all 4 y. Initially, in 2000, the sex ratio of legal-size lobsters was comparable between the two areas. In the two subsequent years (2001-2002), few legal-size females were taken in the Narrows in spring and none were taken in the fall (Table 3A). In fall 2003, 33% (10 of 30) of the legal lobsters taken in the Narrows were female, approaching the 49% taken in the LIST survey, but none were egg-bearing. Thus, in 4 y of sampling, there was a near absence of legal-size egg-bearing females in the Narrows catch. For sublegal size lobsters, the percentage of females in the catch was not different between the two areas (Table 3A, Fig. 9). However, the percentage of sublegal females that were egg-bearing was significantly lower in the Narrows catches compared with the standard LIST catches for all 4 y (0.7% to 10.1% vs. 10.0% to 24.5%, respectively; goodness of fit [chi square] > 17.0, DF = 1, P < 0.01).


A similar pattern was seen in the trap catches during the WLISTS in 2003. The percentage of females decreased from east to west, except for sublegal size females in the fall, which were more consistent in all three areas (Table 3B). The percentage of egg-bearing lobsters decreased from east to west in the fall for both size classes, and was similar to percentages found for sublegal size lobsters in the fall trawl survey in the Narrows (Fig. 10). Numbers of all lobsters dropped when bottom dissolved oxygen fell below 4 ppm and water temperatures rose above 18[degrees]C. Numbers returned in the fall concurrent with increasing dissolved oxygen and dropping water temperature. This pattern was particularly pronounced for egg-bearing females (Fig. 11).


Fisheries Dependent Data

The composition of the commercial catch in terms of percentage by sex and egg-bearing status above and below legal size has shown only subtle changes since the die-off. For eastern and central samples taken July to October, the percentage of females in the catch has increased from approximately 60% to 65% to 75% to 80% over the last 20 y (Fig. 12). For western samples, taken during the same months, the percentage of females in the catch increased in the 1990s but then declined after the die-off. In 2003, only 43% of the observed catch in the west was female, a substantial decline from previous years and repeating a pattern seen in 1988 to 1992. The percentage of those western females that were egg-bearing has declined from an average of 12% in 1992 to 1999 to 6% in 2000 to 2003 for sublegal sizes. This is a significant decrease ([chi square] DF = 9, P = 0.02). The percentage of legal-size egg bearers was always low, but also dropped from 1.7% in 1992 to 1999 to 1.2% in 2000 to 2003. This change is not statistically significant (DF = 9, P = 0.33). Note that regulations affecting the minimum legal size have not changed since 1991.


One aspect of the commercial catch that has changed more obviously since the die-off is the incidence of dead lobsters in the central and western basin (Fig. 13). The incidence has increased from a very rare event (<0.5% of the observed catch) to a more common one (2% to 3% of the observed catch). The incidence of mortality seems to follow a pattern linked to high summer temperatures recorded in 1999 and 2002, with cooler temperatures recorded in 2000, 2001 and 2003 (Fig. 6). In the western basin, mortality is linked to summer water temperatures over a longer time-period. A significant correlation exists between mean bottom water temperature and observed mortality in commercial seasampling, averaged for each month data are available August to October 1996 to 2003 (DF = 34, [r.sup.2] = 0.24, P < 0.01, Fig. 14).



The mark/recapture results indicate that most lobsters in Long Island Sound have limited movement and no discernable seasonal migration in or out of the Sound. The large majority of lobsters recaptured in the western and central basins over a 3-y period were initially captured and released in the same area. Although lobsters tagged in the eastern basin showed no movement to the west, there was movement documented in and out of the eastern margin of the Sound. The intensive fishery within LIS and in adjacent water bodies maximized the probability of encounter if tagged lobsters had moved greater distances from their release point. On the other hand, the fact that multiple recaptures were common indicated that the presence of the fishery probably did not preempt movement. These results imply that the Sound's western lobsters could be resident for most if not all of their adult life, at least until they are well over legal size. Similar conclusions were drawn from tagging studies carried out in the western Sound in 1978 to 1979 (Briggs & Mushacke 1984) and throughout the Sound in 1967 to 1970 (Lund et al. 1973). Lobsters tagged in the eastern Sound by Millstone environmental laboratory staff showed that in 2003, 92% to 99% of the lobsters tagged at each station were recaptured at those very same stations (DRS 2003). The 25-y data series generated by the Millstone tagging program show consistent results: 92% of all tagged lobsters recaptured in commercial pots were recaptured within 5 km of the Millstone tagging stations. Those few lobsters that moved more than 5 km moved east or southeast with only a minimal number of lobsters recaptured in the west over the 25-y study (DRS 2003). All of these studies support the hypothesis that the Sound's western lobster population is nonmigratory.

Genetic analyses (Crivello et al. 2005) also support the view that biologic communication among lobsters in the western Sound and other areas is limited. This study found more genetic similarity between lobsters from the eastern and central basins than from the western basin and other areas of the Sound. This study also indicated limited biologic communication between western basin lobsters and the offshore population in the Hudson Canyon area.

Conditions throughout the Sound were favorable for recruitment of young in the early 1990s, allowing the lobster stock to increase to historic high abundance. This enhanced recruitment ended abruptly with the die-off. A similar trend was seen in Rhode Island research survey catches (Lynch 2004), where abundance of small lobsters increased through the 1990s followed by a decline to record lows. Trends in abundance for the two surveys are significantly correlated (DF = 18, r = 0.79, P < 0.01). Whatever factors were at first favorable and then unfavorable for lobster production seem to be regional in nature. Abundance indices in the Sound were negatively correlated to average summer bottom water temperature. These results therefore point to regional bottom water temperature trends as playing a key role in aiding the stock to increase as well as contributing to its abrupt decline.

Abundance in the Narrows, hardest hit by the die-off, was apparently similar to the rest of the Sound immediately after the die-off. However, 2 and 3 y after the die-off, the Narrows showed a deficit of females compared with the rest of the Sound. Of the females caught in the Narrows by trawl, no legal-size and few sublegal-size lobsters were egg-bearing. The composition of the commercial trap catch and the research trap catch in the western basin corroborated evidence of a decline in the percentage of females, and a decline in the percentage of females that were egg-bearing, following the die-off. It appears that eggbearing females may have been most vulnerable to whatever mortality factors caused the die-off event. They either died at a higher rate than other lobsters, were unsuccessful in extruding or carrying eggs or both. For sublegal size classes, female abundance was negatively correlated with summer bottom water temperature.

Much of the die-off was not directly enumerated as observed mortality measured by sea samplers. Nevertheless, the percentage of dead animals in the portion of the commercial catch that was observed increased 3- to 4-fold after 1998. The months with the highest observed mortality were those with the highest bottom water temperature, often above 20[degrees]C as recorded by the CT DEP Water Quality Monitoring Program. Temperatures above 20[degrees]C have been shown to cause a variety of stress responses and mortality in lobsters held in the laboratory (Powers et al. 2004, Simpson et al. 2003) in addition to facilitating the spread of diseases. Other factors, such as low dissolved oxygen, also may have played a role in the higher than normal mortality recorded in 1999. However, there is a significant correspondence between increased mortality and increased bottom water temperature over 8 y, 1996 to 2003 inclusive, in the western basin.

In 1991, when average summer water temperatures in the Sound were also above 20[degrees]C, the population experienced a mortality event triggered by a severe outbreak of gaffkemia (Briggs 1991, 1992), a lethal septicemia caused by the bacterium Gaffkya homari. American lobsters infected with G. homari in the laboratory died on average in 2 d when kept at 20[degrees]C while it took 84 days at 5[degrees]C and no deaths were recorded at 1[degrees]C (Stewart et al. 1969). These researchers state that temperature is a key factor in the progression and severity of this and other diseases in lobsters. Beginning in 1999, there were four consecutive summers when average bottom temperature was near or above 20[degrees]C. A more comprehensive study of temperatures throughout the Sound (Wilson & Swanson 2005) corroborates the fact that temperatures in these years were well above normal for most of the summer. In 1999, many lobsters were diagnosed with a neural parasitic disease caused by infection with paramoebae (Mullen et al. 2005) instead of gaffkemia as was seen in 1991. The 1999 die-off was probably more severe because of the longer duration of elevated summer temperatures and the fact that the population had built up to historic high abundance prior to 1999 when average temperatures were lower. The pattern in observed mortality, and the pattern in abundance, documented here over the decade preceding 1999 and several years afterward appear to confirm that high water temperature was a significant contributing factor in at least two die-off events in Long Island Sound.


Aitchison, J. & J. Brown. 1957. The lognormal distribution with special reference to its uses in economics. London: Cambridge University Press. 176 pp.

Blake, M. 1998. Connecticut lobster (Homarus americanus) population studies. CT Dept. Environmental Protection, Marine Fisheries Division. US Dept. Commerce, NOAA NMFS Interjurisdictional Fisheries Act Grant 3-IJ-86 Final Report. 143 pp.

Briggs, P. 1992. A report on the informal meeting on lobster mortalities in Long Island Sound. Milford, CT, February 25, 1992. NY State Dept. Environmental Conservation. 5 pp.

Briggs, P. 1991. 1991 lobster die-off chronology, 9/23-10/18/91. NY State Dept. Environmental Conservation. 2 pp.

Briggs, P. & F. Mushacke. 1984. The American lobster in western Long Island Sound: movement, growth and maturity. NY Fish Game J 31(1): 21-37.

CT DEP Environmental Protection (CT DEP). 2000. Impact of 1999 Lobster Mortalities in Long Island Sound. Bureau of Natural Resources, Fisheries Division. 47 pp.

Crivello, J., D. Landers, Jr. & M. Keser. 2005. The genetic stock structure of the American lobster (Homarus americanus) in Long Island Sound and the Hudson Canyon. J. Shellfish Res. 24(3):841-848.

Dominion Resource Services (DRS). 2003. Monitoring the marine environment of Long Island Sound at Millstone Power Station. Annual Report 2003. Prepared by the staff of Millstone Environmental Laboratory. 282 pp.

Gottschall, K. & D. Pacileo. 2002. Marine finfish survey, part 1: Long Island Sound trawl survey. In: A study of marine recreational fisheries in Connecticut. CT Dept. Environmental Protection, Marine Fisheries Division. US Dept. Interior, Fish and Wildlife Service Federal Aid in Sport Fish Restoration Grant F-54-R 21 Annual performance report. 176 pp.

Lund, W., L. Stewart & C. Rathbun. 1973. Investigation on the lobster. US Dept. Commerce, NOAA NMFS Commercial Fisheries Research and Development Act Grant 3-130-R final report. 188 pp.

Lyman, M. & D. Simpson. 2002. Cooperative interagency resource monitoring. In: A study of marine recreational fisheries in Connecticut. CT Dept. Environmental Protection, Marine Fisheries Division. Federal Aid in Sport Fish Restoration Grant F-54-R-21 annual performance report. 176 pp.

Lynch, T. 2004. Assessment of recreationally important finfish stocks in Rhode Island coastal waters, coastal fishery resource assessment trawl survey, 1979-2003. RI Dept. Environmental Management, Division of Fish and Wildlife, Marine Fisheries. US Dept. Interior, Fish and Wildlife Service Federal Aid in Sport Fish Restoration Grant F-61-R annual performance report. 38 pp.

McKown, K., R. Burgess & J. Hayden. 2004. Distribution, movement, and health of American lobster (Homarus americanus) in New York waters with emphasis on western Long Island Sound. NY State Dept. Environmental Conservation. US Dept. Commerce, NOAA NMFS Fishery Disaster Relief Grant NA 16FW1327 semi-annual report. 10 pp.

Mullen, T., K. Nevis, C. O'Kelly, R. Gast & S. Frasca, Jr. 2005. Nuclear small-subunit ribosomal RNA gene-based characterization, molecular phylogeny, and PCR detection of the Neoparamoeba from western Long Island Sound lobster. J. Shellfish Res. 24(3):719-731.

National Oceanic and Atmospheric Administration (NOAA). 2004. Commercial fishing statistics. Available at: index.html

Powers, J., G. Lopez, R. Cerrato & A. Dove. 2004. Effects of thermal stress on Long Island Sound lobsters, H. americanus. Presentation at second working meeting of LIS Lobster Research Initiative. May 3-4, Groton, Connecticut.

Simpson, D., C. Giannini, K. Gottschall, P. Howell & D. Pacileo. 2003. Assessment and monitoring of the American lobster resource and fishery in Long Island Sound. CT Dept. Environmental Protection, Marine Fisheries Division. US Dept. Commerce, NOAA NMFS Disaster Relief Grant NA16FW1238 semi-annual performance report. 87 pp.

Smith, E. 1977. Some aspects of catch/effort, biology, and the economics of the Long Island Sound lobster fishery during 1976. CT Dept. Environmental Protection. US Dept. Commerce, NOAA NMFS Commercial Fisheries Research and Development Act Grant 3-253-R-1 final performance report. 97 pp.

Stewart, J., J. Cornick & B. Zwicker. 1969. Influence of temperature on gaffkemia, a bacterial disease of the lobster Homarus americanus. J. Fish. Res. Board Can. 26:2503-2510.

Wilson, R. & L. R. Swanson. 2005. A perspective on bottom water temperature anomalies in Long Island Sound during the 1999 lobster mortality event. J. Shellfish Res. 24(3):825-830.


(1) Connecticut Department of Environmental Protection, Marine Fisheries Division, Old Lyme, Connecticut 06371; (2) New York State Department of Environmental Conservation, 205 N Belle Mead Rd., East Setauket, New York 11733

* Corresponding author. E-mail:
Summary of effort and catch of lobsters in the Long Island Sound
Trawl Survey, spring and fall 1984-2003.

 Total % of
 Number of Tows With
 Number Lobsters Lobsters
Year of Tows Caught Catches

 Spring Fall Spring Fall Spring Fall
1984 32 70 446 2019 72% 76%
1985 46 80 630 959 57% 69%
1986 116 80 905 1646 67% 61%
1987 120 80 1690 1850 63% 76%
1988 120 80 778 1333 65% 66%
1989 120 80 1945 1502 75% 63%
1990 120 80 2979 2386 73% 76%
1991 120 80 4432 4032 81% 78%
1992 80 80 3002 5159 76% 69%
1993 120 120 5031 7608 74% 76%
1994 120 120 2246 6881 73% 74%
1995 120 80 5741 4202 76% 68%
1996 120 80 5760 3721 68% 78%
1997 120 80 8100 8368 71% 81%
1998 120 80 13037 3177 83% 71%
1999 120 80 10296 3620 78% 79%
2000 120 80 8321 2153 82% 73%
2001 120 80 4214 1413 77% 58%
2002 120 80 3279 601 73% 59%
2003 120 80 1562 1363 73% 64%

 Arithmetic Geometric Geometric
Year Mean Mean Mean

 Spring Fall Spring Fall Spring Fall
1984 13.94 28.84 7.09 7.41 9 11
1985 13.70 11.99 3.10 3.33 18 19
1986 7.80 20.58 2.76 4.71 19 14
1987 14.08 23.13 3.29 5.94 17 13
1988 6.48 16.66 2.22 3.54 20 18
1989 16.21 18.78 3.76 3.75 16 17
1990 24.83 29.83 5.31 7.29 13 10
1991 36.93 50.40 7.74 9.84 6 7
1992 37.53 64.49 7.80 9.52 5 8
1993 41.93 63.40 6.70 11.26 11 2
1994 18.72 57.34 4.06 10.13 14 5
1995 47.84 52.53 8.31 8.05 4 9
1996 48.00 46.51 6.78 10.05 10 6
1997 67.50 104.60 7.67 19.60 7 1
1998 108.64 39.71 18.52 10.47 1 4
1999 85.80 45.25 12.49 11.18 2 3
2000 69.34 26.92 11.01 6.82 3 12
2001 34.83 17.66 7.56 4.28 8 15
2002 27.32 7.51 6.31 2.68 12 20
2003 13.02 17.04 3.89 4.18 15 16

Percentage of recaptured lobsters by zone of release.
Recaptures by zone are tallied as a percentage of the release
zone total. Number of recaptures, including multiple recapture
of the same lobster, are listed for each zone (total individual
lobsters equals 1,729).

Tagged Lobsters Recaptured (Zone Percent)

Basin Released Zone 1 Zone 2 Zone 3 Zone 4 Zone 5 Zone 6

West Zone 1 93.4 5.6 1.0 0 0 0
West Zone 2 1.8 89.3 8.8 0 0 0
Central Zone 3 0.2 1.3 94.5 4.0 0 0
Central Zone 4 0 0 6.6 93.2 0.2 0
East Zone 5 0 0.8 1.6 0.8 83.9 12.9
B I Sound Zone 6 0 0 0 0 13.1 * 86.9

Tagged Lobsters
 Number of
Basin Released Recaptures

West Zone 1 196
West Zone 2 441
Central Zone 3 620
Central Zone 4 499
East Zone 5 124
B I Sound Zone 6 429

* includes 3 recaptures southeast of Block Island
Total recaptures: 2309

Sex ratio (percent females) and the percent of females that were
egg-bearing by size class. Spring and fall catches, 200-2003, from the
Long Island Sound Trawl Survey (LISTS) versus trawl catches in the
Narrows (A) showed similar percentages by area as summer and fall
2003 catches from the Western Long Island Sound Trap Survey (B).

 % Females Egg-bearing

Legal Size Narrows LISTS Narrows LISTS

2000 Spring 35.3 34.2 0.0 20.6
 Fall 45.0 29.8 * 5.0 58.5
2001 Spring 18.2 34.9 0.0 28.1
 Fall 0.0 51.9 ** 37.0
2002 Spring 16.7 35.6 0.0 24.3
 Fall 0.0 33.3 ** 100.0
2003 Spring 12.5 30.9 0.0 11.8
 Fall 33.0 49.1 0.0 30.8

 % Females in Catch % Females Egg-bearing

Sub-legal Size Narrow LISTS Narrows LISTS

2000 Spring 52.0 56.1 10.0 13.3
 Fall 42.5 44.4 2.7 15.7
2001 Spring 49.3 48.5 0.7 10.0
 Fall 36.0 41.8 5.1 22.1
2002 Spring 44.4 51.3 2.8 10.0
 Fall 32.2 37.3 8.5 24.5
2003 Spring 49.4 45.3 9.5 13.8
 Fall 43.5 51.9 7.5 12.6

* 1 of 20 lobsters was egg-bearing

** no females captured

 % Females in Catch % Females Egg-bearing

Legal Size 1 2 3 1 2 3

2003 Summer 6.8 13.8 27.9 0.0 0.3 1.2
 Fall 10.1 21.1 27.8 0.7 5.6 6.6

 % Females in Catch % Females Egg-bearing

Sub-Legal size 1 2 3 1 2 3

2003 Summer 33.3 27.9 40.9 0.9 0.7 1.9
 Fall 9.8 25.3 38.1 0.7 3.5 8.2
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Article Details
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Author:Hayden, Jed
Publication:Journal of Shellfish Research
Geographic Code:1USA
Date:Oct 1, 2005
Previous Article:The genetic stock structure of the American lobster (Homarus americanus) in Long Island Sound and the Hudson Canyon.
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