Characterising shelter preferences in captive juvenile Jasus edwardsii (Palinuridae)

Any attempt to enhance rock lobster production by increasing survival after settlement, or by ongrowing or outplanting young juveniles, requires knowledge of the shelter preferences of young juveniles. For juvenile Jasus edwardsii in the wild these are not well known. Information available suggests that juveniles up to c. 35 mm carapace length (CL) occupy shelters that generally conform closely to their body dimensions but that larger juveniles use shelters of more variable dimension, often much larger than their body size. We investigated mainly physical factors important in shelter choice by 15–59 mm CL (c. 2–24‐month‐old juveniles) in laboratory tank experiments. In overnight tests, all sizes of juvenile lobster chose to occupy holes (shelters with sides) over open horizontal gaps. Preference for open horizontal gaps versus horizontal crevices (where the height reduces from a maximum at the mouth to zero at the opposite end) was much less clear‐cut; choice varied according to lobster size. For the number of entrances into holes, there was evidence for an ontogenetic shift in preference, small lobsters preferring two openings over one, whereas those >30 mm CL (c. 9 months old) preferred one over two. For lobsters <40 mm CL, the hole size and gap size preferences revealed were generally consistent with the field evidence for J. edwardsii in that there was a close and proportional relationship between lobster size and shelter size; what differed was that the open gaps chosen in the tanks by the smallest lobsters (15–19 mm CL) were larger than the holes used in the tank experiments and 30–50% larger than those reportedly used in the field. For lobsters >40 mm CL, the holes and gaps chosen in the tanks were generally larger and more variable in size, as in the field.     

Comparison of catches on two types of collector of recently settled stages of the spiny lobster (Panulirus argus), Florida,United States

This study compared catches of Panulirus argus pueruli and very young juveniles between Hunt and Sandwich collectors at Long and Big Munson Keys, Florida, United States. Catch comparisons were made over the peak puerulus settlement period between February and July 2002, using six Sandwich and six Hunt collectors at each site. The collectors were set out in arrays and the relative positions of the two collector types were reversed each month after they had been checked and the catch removed. A total of 3470 pueruli and juveniles were collected; 2011 and 1459 by Sandwich and Hunt collectors, respectively. Sandwich collectors caught an average of 5.43 more pueruli and juveniles per check than Hunt collectors, with this difference being significant for catches of clear pueruli (P1s), pigmented pueruli (P3s), and juvenile stages (J1s and J2s) (P < 0.05), but not for catches of semi‐pigmented pueruli (P2s). The catches made by both collector types were highly dependant on the month of collection and site of the collectors (P < 0.01). Catches were generally not influenced by the location of the collector in the array (P = 0.50), but corner collectors caught significantly fewer P1s, P2s, P3s, and J1s and J2s than all other collectors (P < 0.01). Conditioning time influenced the total catch (P < 0.01) but was not significant for all individual P1s, P2s, P3s, and J1s and J2s stages of development. Overall, the time taken for collectors to condition in Florida was less than the Sandwich collectors used for P. cygnus in Western Australia.     

Temperature effects on the embryo development and hatching of the spiny lobster Sagmariasus verreauxi

Factors affecting the development of the embryos and production of larvae of the spiny lobster Sagmariasus verreauxi were investigated. Mature lobsters were collected from the fishery in New Zealand and held in captivity until they moulted, mated, and extruded eggs. For females, moulting took place in winter (July/August) and mating occurred 58–88 days later in early spring. The ovigerous females were then held at three temperatures and embryo development monitored at approximately weekly intervals. Mean times to hatch were 55, 75, and 130 days at 20°C, 17°C, and 13°C respectively. The total number of larvae that hatched from each female ranged from 0.97 to 1.4 million. The theoretical temperature at which embryo development ceases (a biological zero) for S. verreauxi, of 9.4°C, was calculated from data on the appearance of the median eye, the eyes and the chromatophores, and the time to hatch. An eye index formula was also derived to allow prediction of time to hatch at a range of temperatures using the cumulative difference between the rearing temperature and the biological zero. First instar phyllosomas from embryos reared at 20°C were significantly smaller than those from 17°C and 13°C but there was no significant difference in fitness. This study shows that hatching can be spread over a number of months, without significantly affecting larval quality, simply by manipulating holding temperature.     

Measurement of bacterial water pollution and the log‐normal distribution (note)

Examination of bacteriological, water pollution in river and nearshore ocean waters of southern Hawke Bay suggests that presentation and analysis of data expressed in terms of the median, as stipulated by New Zealand water pollution legislation, is often unsatisfactory. Data distributions are non‐normal and statistical comparisons over time and area difficult. These difficulties can be largely overcome by a simple log transformation of data.     

The Hispaniola Fluvial System and its Morphostructural Context

This paper presents results of the geomorphological study of river elements for a morphostructural characterization of Hispaniola. The fluvial system and its primary and secondary drainage divides were delimited using a specially developed methodology. More than 120 fluvial basins were studied. The largest rivers are the sixth-order Yaque del Norte and Yaque del Sur. The fluvial density is in the range of 0.08-4.0 km/km², with highest values in the Cordillera Central. There are two large hydrological regions, the Western and the Eastern, with a northeastern transverse diagonal boundary, coinciding with the direction of the Beata Escarpment. Using quantitative data to characterize the morphostructure of the fluvial network in Hispaniola enabled us to make comparisons with a Cuban network. As is shown, the river pattern in Hispaniola is basically tectonic, with a remarkable directional diversity in the main first-order drainage divide. In the Caribbean area, Eastern Cuba is the only other location with this pattern.     

Ecohydrology and water resources management: a pilot study in Trinidad

Abstract

An area of rainforest in Trinidad (10°N, 61°W) is remarkably rich in biodiversity, and receives the highest amount of rainfall in the island due to its orography and the dominant northeast trade winds. However, a year-round transfer of water from its pristine rivers is likely in the future, with ecological consequences. The results of a pilot study are presented, based on a simple, and graphical, segment-scale multi-objective methodology for the estimation of the optimal instream flow of the 13 rivers in this area. This methodology is based on a dimensionless ecohydrological factor, Δ, which enables the required hydraulic mean depth at a river cross-section to be expressed in terms of the average species length at maturity for a target group of amphibians, birds, fish, mammals and reptiles. Moreover, the methodology considers the socio-economic cost of ecological degradation brought about by streamflow abstraction, as well as the economic benefit of the same. An example illustrates the estimation of optimal instream flow for a value of Δ and, thereby, the corresponding optimal river intake operating rule, based on the hydraulic characteristics of a 0.1 km segment of one of the rivers, for the 20-year average dry (January—May) and wet (June–December) seasons. The limitations of the pilot study, and areas for further research, are also highlighted with a hope that it will ultimately evolve into a decision-making tool for water resources management.     

The Geologic Evolution of the Southern Sierra de Guanajuato,Mexico: A Documented Example of the Transition from the Sierra Madre Occidental to the Mexican Volcanic Belt

Geologic mapping and new K-Ar and ⁴⁰Ar/³⁹Ar geochronology of the southeastern Sierra Madre Occidental (SMO), at its intersection with the northern margin of the Mexican Volcanic Belt (MVB), indicate the occurrence of three volcanic groups. The oldest group corresponds to the SMO, and includes 29 to 22 Ma voluminous ignimbrites and 30 Ma andesites and rhyolites. The youngest group includes widespread basaltic-andesitic lava plateaus that yielded ages from 14.6 to 8.8 Ma and are interpreted as the beginning of the MVB. From 22 to 14.6 Ma, volcanic activity in the area was significantly reduced, but did not cease entirely. We refer to the third group as transitional volcanism, which is dominated by andesitic and rhyolitic lava domes but also includes high-grade andesitic ignimbrites. We conclude that the change from volcanism proper of the SMO to that of the MVB was gradual with respect to age and drastic with respect to composition and style, from a voluminous-silicic-ignimbrite domain to a widespread basaltic-andesitic-lava plateau domain. This change may have been related to major plate tectonic reorganizations within the interval from 25 to 12 Ma that involved the waning of subduction of the Farallon plate west of northern Mexico and the associated southward migration of the triple junction of the Pacific-Farallon-North America plates, the subsequent break-up of the Farrallon plate into the Guadalupe and Cocos plates, and the counterclockwise and clockwise rapid rotation of the ridge between them around 16 to 12.5 Ma.     

Scaling Caribbean (in)dependence

Recently there has been much ado about the territorial implications of globalization. Geographers have made a significant contribution to these debates, pointing to the tension between forces of deterritorialization and those of re-territorialization. In particular, there is a growing body of work in political and economic geography that draws attention to processes of re-scaling where, at the same time as scales such as the nation-state appear threatened, new scales of economic, political and social regulation emerge. Much of this literature, however, focuses on the ability of already powerful states to re-scale their activities and manage the border crossing abilities of global capital. In this paper I examine the process of supra-national regional integration in the Caribbean as an example of re-scaling and re-territorialization in a post-colonial context. I draw attention to the historic permeability of Caribbean states and argue regionalism in the Caribbean needs to be viewed as part of a longer process of defining economic, political and cultural independence in what, for post-colonial states, has always been an interdependent world economy. This analysis suggests that while new scales can be understood as spatialized attempts to manage changing global economics, they are also ambivalent productions, and as such, sites of resistance as well as domination and regulation.