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Two morphometric relationships, carapace length versus total length (CL versus TL), and carapace length versus weight (CL versus W), were estimated for the spiny lobster Palinurus elephas fished in northwestern Sardinia. The calculations were done for both sexes and for the years 1998 and 1999. The power function y = ax b was used in both relationships. The first derivate dY/dCL = abCL b−1 , where Y is either TL or W was used to study the growth tendency of TL and W in relation to CL. The results showed no interannual differences in the CL versus TL relationship for both sexes. A negative allometry, b < 1, was found for males which was also reflected in their decreasing growth rate of TL in relation to CL. However, this negative allometry would not have been detected if the function y = a + (bx) had been used since it yields only isometric growth. Conversely, the CL versus W relationship showed significant interannual differences for both sexes and a general negative allometry, b < 3. This negative allometry was more stressed for males in both years which also was reflected in their lower W growth rate in relation to CL. Consequently, for a better estimation of the W from the CL versus W relationship it is recommended to calculate this yearly using local values, and limiting the application of the calculated regression only to the range of measures employed. Finally, the use of some condition indices in relation to the negative allometry and the interannual variability in the CL versus W relationship is also discussed.

The Southwestern Atlantic is often perceived as remote region, yet it is not immune to biological invasions. Patchy information on historical community composition hinders our ability to identify introductions to coastal ecosystems in this region. Hull fouling is an under-managed shipping vector that likely continues to transport large numbers of marine species worldwide. The port of Mar del Plata is a comparatively well-studied shipping and commercial hub that may serve as an observatory to monitor new introductions to the Argentine coast. Following detection of nonindigenous isopods during preliminary port sampling in 2007-2008, we organized regular port surveys aimed at assessing the level of population establishment and evaluated hull fouling as a potential introduction vector in the Port of Mar del Plata. In 2011-2012, we conducted 12 monthly dive surveys of port isopod communities in combination with three opportunistic surveys (two in-water, one in dry-dock) of hull fouling communities attached to a domestic research vessel during consecutive port calls at its base in this port. Replicate biofouling samples from underwater dock structures and the vessel's hull were collected by scraping invertebrates in 20 × 20 cm quadrats (even surfaces) and 1000 cm 3 of biofouling organisms (uneven surfaces). Both in port-and hull-fouling communities, we discovered the presence of the nonindigenous isopods Dynamene edwardsi and Paracerceis sculpta. This report constitutes the first detection of these two global marine invaders in American and Argentine waters, respectively. They likely represent relatively recent introductions to this corner of the world's oceans, yet our data indicate that both species are currently well established in Mar del Plata. These results demonstrate (for the first time in the case of D. edwardsi) the potential for hull fouling to disperse both species, and raise a warning on their potential expansion to other Southwestern Atlantic ports and Antarctica in a near future. Research on the marine communities of the Southwestern Atlantic is pressingly needed to establish pre-invasion communities and detect new introductions. Simultaneous surveillance of ports (invasion hubs) and vessels (vectors) can effectively detect invaders and inform prevention efforts in this region.

Non-indigenous ascidians are transported across oceans in vessel-hull fouling communities, and regional traffic plays a role in their secondary spread. We found the ascidian Ascidiella scabra (M&uuml;ller, 1776) in the hull-fouling community of an oceanographic vessel confined to waters of the southwestern Atlantic and Southern Oceans. The previously known distribution of this species was restricted to its native area (Mediterranean Sea and northeastern Atlantic); its presence in the southwestern Atlantic may have been masked in the past by the occurrence of its congener Ascidiella aspersa (M&uuml;ller, 1776).

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