Investigating Poor Growth of Hard Clams in New Jersey

Project Overview

Project Type: Partnership
Funds awarded in 2022: $28,713.00
Projected End Date: 01/31/2025
Grant Recipient: University of Connecticut
Region: Northeast
State: Connecticut
Project Leader:
Dr. Sylvain Deguise, DMV, PhD
Connecticut Sea Grant, University of Connecticut


  • Animals: shellfish


  • Animal Production: aquaculture
  • Education and Training: decision support system, extension, on-farm/ranch research
  • Farm Business Management: risk management

    Proposal abstract:

    In New Jersey (NJ), aquacultured hard clams (Mercenaria mercenaria) comprise a significant portion of the market supply for this highly demanded commercial species.  Since 2015, farmers have observed a significant reduction in hard clam growth rates and survivorship on previously productive leases in multiple estuaries. This study will investigate the patterns and cause of growth declines and mortality to provide farmers with information needed to make critical decisions about farming practices in the future.  Through partnerships with NJ farmers, hard clams will be sampled from two aquaculture sites in different estuaries in the state. To determine short term growth patterns, samples will be collected monthly from April - October to assess condition index (CI), which is a widely used indicator for molluscan bivalve health status, environmental variables, and more (Zeng and Yang, 2021).  These measurements will be paired with an age analysis using shell ring measurements to evaluate  growth trends over the past decade.  These data will be compared with continuous water quality measurements collected by the NJ Department of Environmental Protection (NJDEP) to determine if there is evidence of a relationship between environmental variables and growth.

    We will coordinate with Sea Grant extension and NJDEP to present our findings at NJ Shellfish Council meetings. We will also host a workshop at the Milford Aquaculture Seminar to discuss with growers and scientists across the Northeast region. Findings will be distributed more broadly through NOAA Fisheries communications platforms online.

    Project objectives from proposal:

    Objective 1: To identify periods of slow growth during the annual production season using condition index as an indicator of metabolic energy balance. Data will be compared between sites and against historical data to describe timing and severity of changes in growth.


    Objective 2: To use shell aging analysis of older clams to describe long-term patterns in hard clam growth within and between growing sites. 

    Objective 3: Informed by observations from Objectives 1&2, identify changes in seasonal and long-term trends in environmental variables. Assess the sensitivity of hard clam growth and survival to conditions to provide insight on the regionally observed poor clam production. 

    Outcomes/Deliverables: Quantification of the slow growth effects being observed by New Jersey clam farmers. Quantitative understanding of the extent and severity of this issue will aid farmers in attracting support to explore options to counteract the problem. Identifying the temporal sequence associated with poor performance will better inform future research so that studies are relevant to the problems facing the commercial sector. We intend for the results of the correlative study between environmental variables and clam performance to be applied to farm management and siting practices to help farmers make informed choices about their production plans.

    Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.