Program specialist, Tony Petrillo holding an oyster toadfish (Opsanus tau), May 2006. Kurt Gottschall, CTDEEP.

Long Island Sound Trawl Survey

The Long Island Sound Trawl Survey (LISTS) started in 1984 and is an ongoing effort that provides a long-term monitoring of the abundance, biomass and size composition of marine fishery resources along with environmental factors within Long Island Sound.

Sampling Location

LISTS is conducted from longitude 72° 03' (New London, Connecticut) to longitude 73° 39' (Greenwich, Connecticut). The sampling area includes Connecticut and New York waters from 5 to 46 m in depth and is conducted over mud, sand and transitional (mud/sand) sediment types. Sampling is divided into spring (April-June) and fall (Sept-Oct) periods, with 40 sites sampled monthly for a total of 200 sites annually. The sampling gear employed is a 14 m otter trawl with a 51 mm mesh codend (Table 1). To reduce the bias associated with day-night changes in catchability of some species, sampling is conducted during daylight hours only (Sissenwine and Bowman 1978).

Survey Design

A map of the state of new york with the most people in each area.

Figure 1. LISTS survey area.

LISTS employs a stratified-random sampling design. The sampling area is divided into 1.85 x 3.7 km (1 x 2 nautical miles) sites (Figure 1), with each site assigned to one of 12 strata defined by depth interval (0 - 9.0 m, 9.1 - 18.2 m, 18.3 - 27.3 m or 27.4+ m) and bottom type (mud, sand, or transitional as defined by Reid et al. 1979). For each monthly sampling cruise, sites are selected randomly from within each stratum. The number of sites sampled in each stratum was determined by dividing the total stratum area by 68 km² (20 square nautical miles), with a minimum of two sites sampled per stratum (Gottschall et al. 2000). Discrete stratum areas smaller than a sample site are not sampled.

Prior to each tow, temperature (C) and salinity (ppt), conductivity (μS/cm) and dissolved oxygen (mg/l) are measured using an YSI model EXO2 data sonde. The EXO2 sonde, captures a full depth profile, and has been used by LISTS since 2017. Previously a hand-held YSI meter was used to obtain surface and bottom measurements, however early in the time series, from 1984 to 1987 no physical data was recorded.

Data Collection and Processing

The survey’s otter trawl is towed from the 15.2 m aluminum R/V John Dempsey for 30 minutes at approximately 3.5 knots. At completion of the tow, the catch is placed onto a sorting table and sorted by species. An aggregate weight by species is obtained, and individuals are weighed for select species that will be collected for ageing. In the beginning of the survey, there was a priority to collect measurements from the most recreationally important finfish (bluefish, scup, summer flounder, winter flounder, and tautog) and invertebrates (lobster and squid). The survey has since expanded, and now obtains length information on all finfish species, and a wider range of invertebrates, and classifies algae. The complete time series of species counted and weighed in LISTS is documented in our most recent annual report. Since 2017, for all species where length was collected, electronic measuring boards were used to capture lengths to the millimeter. For finfish, either fork or total length was collected. Lobsters are measured to 0.1 mm carapace length using calipers. Squid are measured using the mantle length (mm), horseshoe crab measurements were taken using prosomal width (mm) and whelk (knobbed and channeled) shell widths were measured in millimeters. For most analysis, lengths are put into centimeter group bins (e.g., measurements from 100 mm to 109 mm were processed as 10 cm). In addition to length data, age structures are collected from various finfish, including bluefish, scup, summer flounder, winter flounder, tautog, menhaden and weakfish. Annual reports and analysis include, but are not limited to, indices of abundance/biomass, length frequencies and indices at age.

Biologist Dave Ellis, training seasonal resource assistant Katherine Helmer on how to use the electronic measuring equipment, May 2023. Kelli Mosca, CT DEEP.

A boat is in the water near some buildings.

Requesting Data

LISTS encounters and catalogs a wide variety of species, and truly highlights the diversity that can be found in Long Island Sound. From 1984-2023, LISTS has identified 114 finfish species and 65 genus or species of invertebrates.

For more specific detail on LISTS methods, analyses and a full catalog of results please refer to the latest annual report which can be found here: Long Island Sound Trawl Survey.

Data can be requested from the LISTS by contacting either Kurt Gottschall (Fisheries Biologist II) or Kelli Mosca (Fisheries Biologist I). In your request, please including the following:

Your name, position, and affiliation
Background information and detailed description on what (or how) you will be using the data
What data you are interested in (species, count/weight, length, age, abundance, water quality, etc.) and/or specific summary format requested
Your timeframe(s) of interest (specific years, seasons, months etc.)
Your timeframe of when data is desired by
Your contact information, including e-mail address and a phone number to reach you

Contact Information

Kelli Mosca (Fisheries Biologist I)
Phone: (860) 447-4313
Email: kelli.mosca@ct.gov
Long Island Sound Trawl Survey