Possible Demographic Consequences of Intraspecific Shelter Competition Among American Lobsters

Pioneering work by J. Stan Cobb described how habitat architecture and body size scaling affect shelter-related behavior of American lobsters. Subsequent research suggested that shelter availability and competition could set local carrying capacity and demographics for this species. To determine how shelter spacing affects population density, the intensity of intraspecific competition and the distribution of body size for this species, I deployed sets of 10 identically sized artificial shelters spaced at distances of 2.5, 0.5, 1.0, 1.5 and 2.0 meters on otherwise featureless substrate at 10 m depth in mid-coast Maine, U.S.A. Five sets had two parallel strings of five opposing shelters and an additional linear string set 2 to apart without opposing shelters was the most widely separated treatment. Shelters spaced I m apart and closer had higher lobster population densities, more intraspecific competition and higher proportions of empty shelters. Surprisingly, lobsters there were also significantly smaller, declining from 62.7 mm to 50.9 on the carapace (CL) for 2 to linear to 0.25 m spaced shelters, respectively. Nearly all 932 lobsters measured in this study were juvenile (< 90 mm CL) and preharvestable (< 83 mm CL) sized, so mate selection and fishing effects were unlikely. At the scale of the experiment, larger lobsters leave or avoid areas of high lobster population density and intense competition for areas of low population density and relaxed competition (called "demographic diffusion"). Scuba surveys in coastal zones found lobster population densities scale with shelter densities and were highest in boulder habitat where, like the experiment, more than half the shelters were vacant. Fisheries independent scuba and trawl surveys in Maine's shallow coastal zone repeatedly recorded declines of preharvestable, lobsters larger than 60 turn CL in size and increases of those sizes offshore and in deep water. It is possible that this demographic diffusion is driven by behaviors associated with intraspecific shelter competition.

Recruitment Habitats and Nursery Grounds of the American Lobster Homarus Americanus: A Demographic Bottleneck?

We have identified benthic recruitment habitats and nursery grounds of the American lobster Homarus americanus Milne Edwards in the coastal Gulf of Maine, USA, by systematically censusing subtidal sediment, cobble, and ledge substrata. We distinguish lobsters between settlement size (5 mm carapace length (CL) to ca 40 mm CL as the 'early benthic phase' (EBP) because they are ecologically and behaviorally distinct from larger lobsters. EBP lobsters are cryptic and apparently restricted to shelter-providing habitats (primarily cobble substratum) in coastal Gulf of Maine. In these habitats we found average population densities of EBP lobsters as high as 6.9 m-2. EBP lobsters were virtually absent from ledge and sedimentary substrata devoid of vegetation although larger lobsters are commonly found there. It is possible that the requirement for shelter-providing substrata by this life phase creates a natural demographic 'bottleneck' to benthic recruitment for the species. Prime cobble recruitment habitat is relatively rare and comprises ca 11 % of the 60.2 km of shoreline at our study area in midcoast Maine. If this low availability of cobble exists throughout the Gulf of Maine, as other studies indicate, it could limit lobster production potential. We verified the geographic extent of recruitment to cobble habitats censused in 3 of 4 regions spanning ca 300 km of the coastal Gulf of Maine (from Nahant, Massachusetts to Swans Island, Maine). Early benthic phase lobsters were absent from cobble censused in the northeastern extreme of our survey (Swans Island). This pattern is consistent with earlier speculation that relatively cool water temperatures may limit larval settlement in this region.

The Relationship Among Resilience, Forgiveness, and Anger Expression in Adolescents

This study was designed to investigate and describe the relationship among resilience, forgiveness and anger expression in adolescents. The purpose of the study was to explore whether certain adolescent resiliencies significantly related to positive or negative affective, behavioral, or cognitive levels of forgiveness and certain types of anger expression in adolescents. This study also investigated whether there were certain adolescent resiliencies and types of forgiveness that can predict lower levels of negative anger expression in adolescents. This research was built on two conceptual models: Wolin and Wolin's (1993) Challenge Model and the Forgiveness Process Model (Enright & Human Development Study Group, 1991). It was based on a quantitative, single-subject correlational research design. A multiple regression analysis was also used to explore possible effects of resilience and forgiveness on anger expression in adolescents. In addition, two demographic variables, Age and Gender, were examined for possible effects on anger expression. Data were gathered from a convenience sample sample of 70 students in three Maine public high schools using three separate assessment instruments: the Adolescent Resiliency Attitudes Scale (ARAS), the Adolescent Version of the Enright Forgiveness Inventory (EFI), and the Adolescent Anger Rating Scale (AARS). Correlational analyses were done on the scales and subscales of these surveys. Significant relationships were found between several adolescent resiliencies and forms of forgiveness as well as between some adolescent resiliencies and types of anger expression. The data indicated that Total Resiliency significantly correlated with Total Forgiveness as well as Total Anger. The findings also identified particular adolescent resiliencies that significantly predicted types of anger expression, while forgiveness did not predict types of anger expression. The data revealed that Age and Gender had no significant affect on anger expression. These findings suggest that the constructs of adolescent resilience and forgiveness have commonalities that can influence how adolescents express anger, and further suggest that intervention and prevention programs expand their focus to incorporate forgiveness skills. The findings from this study can provide critical information to counselors, therapists, and other helping professionals working with adolescents, on approaches to designing and implementing therapy modalities or developmental school guidance programs for adolescents.