Four years of survey work in the Bay of Gibraltar logged 2,410 dolphin sightings across 593 days at sea. The three species that live here were rarely recorded in the same water at the same time. That result was published on 2 June 2026, and it changes how you should read the ticket you buy at Marina Bay. You are not going out to see three species. You are going out to see one of them, and which one depends on where the boat goes and what month it is. The study ran from 2017 to 2020, off the back of a long running monitoring programme worked from a licensed dolphin watching boat. Observers used 7 by 50 binoculars and logged every sighting by species, age class and GPS position. Total effort came to 25,610 kilometres over 1,690 hours of navigation. [The paper is open access in the Journal of Marine Science and Engineering](https://res.mdpi.com/d_attachment/jmse/jmse-14-01044/article_deploy/jmse-14-01044.pdf). The short beaked common dolphin was the most frequently sighted, with numbers climbing from summer into autumn. The bottlenose was the least, at 102 records in four years. A chi square test found no significant seasonal variation in bottlenose occurrence across years and seasons, which is a statistician's way of saying they are around all the time and never in numbers. Here is the part that matters on a boat. When the researchers measured the gap between a bottlenose sighting and the next sighting of either other species, the distances ran from 261 metres to 12 kilometres, and the time gaps from 33 seconds to 5 hours 38 minutes. Overlaps of 300 seconds or less were infrequent. In the sequences analysed, not one mixed group involving a bottlenose and either other species was recorded. We are going to be straight about the limits of this, because most write ups of a paper are not. The authors ran logistic models and found no statistically significant relationships. They say so plainly, call their own results descriptive rather than explanatory, and point at uneven sampling effort and missing variables such as depth and prey distribution. The pattern is there in the data. The mechanism behind it is not established. A dolphin is above water for about a second at a time, and size will not save you: a common dolphin runs 1.9 to 2.5 metres and a striped one 1.8 to 2.5, so on the water they are the same animal. Learn one marking per species instead. The field marks below follow the standard reference accounts, including [the striped dolphin's distinctive blaze and flank stripes](https://en.wikipedia.org/wiki/Striped_dolphin). The group sizes are the ones actually recorded in this bay. |Species|Size and build|The giveaway|Group size recorded here| |Short beaked common|Roughly 1.9 to 2.5 m, slim, sharp pointed beak|A tan and grey hourglass on the flank, pale gold forward of the dorsal fin|Usually 30 to 90, with aggregations of over 1,000 on several occasions| |Striped|Roughly 1.8 to 2.5 m, slim|Thin dark stripes from the eye to the flipper and along the flank, and a pale blaze sweeping up towards the dorsal fin|Usually 30 to 40 mothers with calves, and summer groups of juveniles up to about 200| |Bottlenose|Roughly 2.5 to 3.5 m, bulky, short thick beak|Plain grey with almost no pattern, and clearly larger than the other two|Usually 10 to 40| Two habits help as much as the markings. Common dolphins here move in loose, fast, noisy groups that often include calves and neonates, and they will ride a bow wave. Striped dolphins leap, and in winter and spring their small juvenile groups of five to twenty animals were often found mixed in with the common dolphins. The bottlenose kept away from both. The Bay of Gibraltar is about 10 kilometres long and 8 kilometres wide, some 75 square kilometres of water with Algeciras on one shore, La Linea at the head and the Rock on the other. [Reference works give its depth as around 400 metres](https://en.wikipedia.org/wiki/Bay_of_Gibraltar). The survey papers are more specific and a little deeper: one submarine canyon runs north to south across the bay in what the researchers call a specular S, bottoming out at 450 metres in the 2026 paper and 460 metres in the same team's 2023 one. We cannot reconcile those two figures and we are not going to pretend they agree. The canyon is why any of this is here. [A 2023 study in the Journal of Environmental Management](https://doi.org/10.1016/j.jenvman.2022.116546) mapped three years of common dolphin sightings and found the pods strung along the canyon's vertical axis, feeding, mating, breeding and rearing calves in a well defined area the authors call critical habitat. The water does the rest. Atlantic water pours in through the Strait on the surface, denser Mediterranean water slides out underneath, tides drag the two layers about, and a local upwelling sits at the mouth of the bay. The result is a small patch of sea that keeps producing food. It is also under heavy pressure. The 2026 paper lists what shares the bay with the dolphins: one o