Anthropogenic habitats such as marinas and docks are focal points for marine invasions, but relatively little is known about the infiltration of nearby natural habitats by these invaders. To address infiltration by four geographically widespread ascidian invaders, we used a two‐step approach: (i) a field survey with equitable sampling in adjacent artificial and natural habitats in British Columbia, Canada, and (ii) a literature review, to infer larger scale patterns across species’ introduced global ranges. Our field survey revealed differential distribution patterns among the four ascidians recorded, with infiltration of natural rocky habitats by two species, Botrylloides violaceus and Botryllus schlosseri. We did not record Didemnum vexillum or Styela clava in natural habitats, though they were both recorded on adjacent artificial structures. Globally, these ascidian species are predominantly found associated with anthropogenic habitats including floating docks, pilings and aquaculture installations, but they have infiltrated natural habitats in some areas of their introduced range. The factors contributing to infiltration of nearby natural benthic habitats remains unclear, but determining which mechanisms are important for encouraging or hindering the establishment and spread of nonindigenous species beyond artificial structures requires survey and experimental work beyond anthropogenic habitats. Such work will aid our understanding of marine introduction dynamics, invasiveness, and associated management implications.

The structure of the retina of the harbour seal, Phoca vitulina richardii, is described. It is shown that the retina of the harbour seal is similar to that of the harp seal, in that it shows little zonation of the inner nuclear layer, possesses large horizontal cells, and has similar nuclear densities within the different retinal layers throughout the retina. The outer nuclear layer is also the thickest of all the retinal layers. Two types of photoreceptor cell, types B and C, were observed with a ratio of roughly 1:23 respectively. This ratio, along with a well-developed and extensive tapetum, indicates a highly light-sensitive retina. The existence of retinal folding in marine mammals is also questioned and discussed.

The trap fishery for Dungeness crabs Cancer magister in British Columbia is regulated by a minimum legal size limit of about 154 mm notch‐to‐notch carapace width (CW). This effectively bars females from the catch in most regional fisheries because few females attain this size. Consequently, in heavily exploited populations, males greater than the minimum legal size are rare and the sex ratio of adults favors females. As is typical of cancrid crabs, female Dungeness crabs mate with males considerably larger than themselves. In light of this and of data we present on male mating activity, sizes of mating pairs, and the degree of exploitation of males, we propose that females greater than about 140 mm CW would have difficulty finding a sexual partner in intensively exploited fisheries. Fewer matings of larger females could result in lost egg production, which suggests to us that increased understanding of the effects of a male‐only fishery on the dynamics of Dungeness crab reproduction is important for confident management.

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Legislated marine "protected" areas are now widely distributed throughout tropical and temperate waters, but the nature of human activities actually restricted in any area varies. This ambiguity about what "protected" means has resulted in contradictory claims as to both the benefits and costs of marine protected areas. Here, we give our perspective on the current status of marine resource protection in Canada in general and British Columbia in particular. We first describe and discuss the history of Canadian marine protected areas established to date. Many areas are claimed to be protected, with little understanding by either the general public or even most marine resource experts as to what human activities are actually regulated by legislative designations. Second, we present an overview of biological reasons and objectives for marine protected areas, followed by a review of both the conservation and fisheries management effects and implications resulting from effective renewable resource protection. Finally, we propose a unique qualitative scheme for classifying and describing marine protected areas of different types to determine relative measures of protection.